ArticlePDF AvailableLiterature Review

Protocatechuic Acid and Human Disease Prevention: Biological Activities and Molecular Mechanisms

Authors:

Abstract

Epidemiological evidence has shown that a high dietary intake of vegetables and fruit rich in polyphenols is associated with a reduction of cancer incidence and mortality from coronary heart disease. The healthy effects associated with polyphenol consumption have made the study of the mechanisms of action a matter of great importance. In particular, the hydroxybenzoic acid protocatechuic acid (PCA) has been eliciting a growing interest for several reasons. Firstly, PCA is one of the main metabolites of complex polyphenols such as anthocyanins and procyanidins that are normally found at high concentrations in vegetables and fruit, and are absorbed by animals and humans. Since the daily intake of anthocyanins has been estimated to be much higher than that of other polyphenols, the nutritional value of PCA is increasingly recognized. Secondly, a growing body of evidence supports the concept that PCA can exert a variety of biological effects by acting on different molecular targets. It has been shown that PCA possesses antioxidant, anti-inflammatory as well as antihyperglycemic and neuroprotective activities. Furthermore, PCA seems to have chemopreventive potential because it inhibits the in vitro chemical carcinogenesis and exerts pro-apoptotic and anti-proliferative effects in different tissues. This review is aimed at providing an up-dated and comprehensive report on PCA giving a special emphasis on its biological activities and the molecular mechanisms of action most likely responsible for a beneficial role in human disease prevention.
Current Medicinal Chemistry, 2012, 19, 2901-2917 2901
1875-533X/12 $58.00+.00 © 2012 Bentham Science Publishers
Protocatechuic Acid and Human Disease Prevention: Biological Activities and
Molecular Mechanisms
R. Masella*,1, C. Santangelo1, M. D’Archivio1, G. LiVolti2,3, C. Giovannini1 and F. Galvano2,3
1Dept. Veterinary Public Health and Food Safety, Istituto Superiore di Sanità, V.le Regina Elena 299, 00161 Rome, Italy
2Dept. of Drug Science, University of Catania, V.le A. Doria 6, 95125 Catania, Italy
3Dept. of Cardiac Surgery, IRCCS Policlinico “San Donato”, San Donato Milanese, Milan, Italy
Abstract: Epidemiological evidence has shown that a high dietary intake of vegetables and fruit rich in polyphenols is associated with a
reduction of cancer incidence and mortality from coronary heart disease. The healthy effects associated with polyphenol consumption
have made the study of the mechanisms of action a matter of great importance. In particular, the hydroxybenzoic acid protocatechuic acid
(PCA) has been eliciting a growing interest for several reasons. Firstly, PCA is one of the main metabolites of complex polypheno ls s uch
as anthocyanins and procyanidins that are normally found at high concentrations in vegetables and fruit, and are absorbed by animals and
humans. Since the daily intake of anthocyanins has been estimated to be much higher than that of other polyphenols, the nutritional value
of PCA is increasingly recognized. Secondly, a growing body of evidence supports the concept that PCA can exert a variety of biological
effects by acting on different molecular targets. It has been shown that PCA possesses antioxidant, anti-inflammatory as well as anti-
hyperglycemic and neuroprotective activities. Furthermore, PCA seems to have chemopreventive potential because it inhibits the in vitro
chemical carcinogenesis and exerts pro-apoptotic and anti-proliferative effects in different tissues. This review is aimed at providing an
up-dated and comprehensive report on PCA giving a special emphasis on its biological activities and the molecular mechanisms of action
most likely responsible for a beneficial role in human disease prevention.
Keywords: Antioxidants, apoptosis, atherosclerosis, bioavailability, cancer, inflammation, phenolic acids, polyphenols, protocatechuic acid,
signaling pathways, type 2 diabetes.
INTRODUCTION
Over the last years great interest has b een growing in the effects
that lifestyle strategies may have on the risk of developing chronic-
degenerative diseases such as cardiovascular diseases, diabetes,
neurodegenerative diseases and cancer. The consumption of a diet
rich in vegetables and fruit seems to exert beneficial healthy effects
because of the high content in fibers, mineral salts, vitamins, and a
large number of non-nutrient phytochemicals such as polyphenols
[1,2]. Nowadays, daily consumption of five portions of fruit and
vegetables is recommended, although there is not guidance on the
specific type of fruit and vegetables to consume [3]. Thus, to date
there is not convincing evidence for the identification of those
vegetable foods that could significantly contribute to chronic-
degenerative disease prevention. The picture is further complicated
by the high number of potentially protective components, e.g.
polyphenols, contained in fruit and vegetables. Dietary polyphenols
comprise a great diversity of compounds among which flavonoids
and several classes of non-flavonoids are distinguished (Fig. 1) [4].
Notably, evidence has been growing on the potential biological
activities that individual compounds can exert, not necessarily
related either to the complexity of the structure or to the abundance
in food sources[5]. In this regard, protocatechuic acid, a catechol-
type o-diphenol phenolic acid (PCA, 3,4-dihydroxybenzoic acid),
has elicited the interest of researchers in th e last few years because
of the antioxidant activity and the additional biological functions it
is able to exert. The aim of this work is to review what is known
about PCA, including distribution in food, metabolic formation, and
bioavailability. Particular attention will be paid to the mechanisms
of action by which PCA might exert potential protective/therapeutic
effects. We will focus on the capability to modulate oxidative
stress, inflammation, and apoptosis processes that, often in
combination one another, play a main role in the pathogenesis of
chronic-degenerative diseases.
*Address correspondence to this author at the Istituto Superiore di Sanità, Viale Regina
Elena 299, 00161 Rome, Italy; Tel: +390649902544; Fax: +390649387101;
E-mail: roberta.masella@iss.it
NUTRITIONAL VALUE OF PCA
PCA is contained in fruit and vegetables, but also in plant-
derived beverages such as tea, white grape wine and in herbal
medicine [6-30], and its content varies considerably depending on
the type of food. In Table 1 are shown the main dietary sources of
PCA. It is important to underscore that numerous factors, such as
ripeness at the time of harvest, environmental factors, and storage,
may affect the polyphenol content of plants (for details see [31-
33]).
Because of its low concentrations in fruit and vegetables, until a
few years ago little attention has been paid to the beneficial effects
of PCA on health. However, recent data have clarified that PCA
concentration in vivo could be higher than the simple quantity
ingested because it is a main metabolite of complex polyphenols,
e.g. anthocyanins (ACNs) [34]. Polyphenols can undergo a great
deal of structural transformation both in vivo and in vitro that will
undoubtedly alter their activity. This is particularly apparent for the
flavonoid subclass ACNs. ACNs are water-soluble pigments
dissolved in the vacuolar sap of the ep idermal tissue of flowers and
fruit [35] to which they impart the peculiar red-orange to blue-
violet colors [36]. ACNs are widely distributed in the human diet:
they are mainly found in fruits, especially those of the berry family,
pomegranate and pigmented varieties of oranges (Tarocco, Mo ro ,
and Sanguinello). For these reasons, their daily intake is much
higher (180-250 mg/d) [37,38] than that of other polyphenols
(estimated at 20-30 mg/d) [39,40]. ACNs are absorbed in animals
and humans as both intact glycosides and metabolite [41-45].
Indeed, they are rapidly metabolized ultimately leading to the
formation of phenolic acids and aldehydes [45]. In particular, at
physiological pH, ACNs easily convert to PCA [46], which is also
abundantly formed and absorbed in the large intestine because of
microbial metabolization [34]. Consequently, PCA deserves great
nutritional interest as main human ACN metabolite that might reach
tissues in such an amount to exert biological healthy effects [47].
ABSORPTION, METABOLISM, AND BIOAVAILABILITY
The absorption of some, but not all, dietary polyphenols occurs
in the small intestine. It is widely accepted that two possible
2902 Current Medicinal Chemistry, 2012 Vol. 19, No. 18 Masella et al.
Fig. (1). Principal classes of polyphenols.
Table 1. PCA Food Content
Dietary sources PCA maximum concentration found in foo d References
Mushrooms (Ramaria botrytis) 34.27 mg/100g dry weight Barros L. et al. [16]
Green Chicory 30.18 mg/100g fresh weight Rossetto M. et al. [235]
Red Chicory 25.71 mg/100g fresh weight Rossetto M. et al. [235]
Black olives 21.00 mg/100g fresh weight Boskou, G. et al. [236]
Black raspberry 8.35 mg/100g dry weight Wu X. et al. [18]
Date, dried 8.34 mg/100g dry weight Al-Farsi M. et al. [237]
Date, fresh 4.49 mg/100g fresh weight Al-Farsi M. et al. [237]
Green olives 2.00 mg/100g fresh weight Boskou G. et al. [236]
Apple Juice 1.64 mg/100ml Gokmen V. et al. [238]
Vinegar 1.62 mg/100ml Natera R. et al. [239]
White wine 1.30 mg/100 ml Ping L. et al. [240]
Blackberries 1.01mg/100g dry weight Zadernowski R. et al. [241]
Red wine 0.72 mg/100 ml Minussi R.C. et al. [242]
Black currant 0.71mg/100g, dry weight Zadernowski R et al. [241]
Grape, raisin 0.68 mg/100g fresh weight Karadeniz F. et al. [243]
Beer (alcohol free) 0.51 mg/100ml Garcia A. et al. [244]
Cauliflower 0.45 mg/100g fresh weight Ping, L. et al. [240]
Almond 0.44 mg/100g fresh weight Milbury P.E. et al. [245]
Virgin olive oil 0.24 mg/100g fresh weight Liberatore L. et al. [246]
Pomegranate, pure juice 0.20 mg/100 ml Poyrazoglu E. et al. [247]
Lentils 0.14 mg/100g fresh weight Duenas M. et al. [248]
mechanisms exist to hydrolysed glycosides. The first mechanism
involves the lactase phloridizin hydrolase (LPH) that is present in
the brush-border of the small intestine epithelial cells [48]. The
released aglycones can enter th e epithelial cell by passive diffusion
as a result of their increased lipophilicity. The second mechanism
involves the cytosolic -glucosidase (CBG) that is present within
Lignans
Proanthocyanidins
POLYPHENOLS
Phenolic acids
Flavones lsoflavones
Flavonols Flavanones
Flavanols/Catechins
Stilbenes
Lignins
Hydroxy benzoic
acids
(R1=R2=OH, R3=H: Protocatechuic acid)
Hydroxy cinnamic
acids
Anthocyanins
(R3’=OH, R5’=H, R3= -O-glycoside: (Cyanidin 3 Glucoside)
R3
R5’
R3’
Flavonoids
Protocatechuic Acid and Human Disease Prevention Current Medicinal Chemistry, 2012 Vol. 19, No. 18 2903
the epithelial cells where th e polar glycosides are transported
through the active sodium-dependent glucose transporter SGLT1
[49].
The polyphenols that are not absorbed in the small intestine
reach the colon where they undergo substantial structural
modifications. In fact the colonic microflora hydrolyze glycosides
into aglycones and degrade them to simple phenolic acids [50, 51].
This is of great importance because specific active metabolites are
produced. Once absorbed, and p rior to the passage into the
bloodstream, the polyphenols, now simple aglycones, undergo
addition al structural modifications through the conjugation process.
The conjugation, mainly methylation, sulfation, and glucuroni-
dation, represents a metabolic detoxication process that facilitates
the biliary and urinary excretion of the polyphenols by increasing
their hydrophilicity (Fig. 2). Therefore, any single polyphenol
generates several metabolites, and the compounds that reach cells
and tissues are chemically, biologically and, in many cases
functionally different from the original dietary form [52]. These
modifications can affect the polyphenol bioavailability and
consequently their biological activity. The term ‘bioav ailability’
means the fraction or compound of an ingested nutrient that reaches
the systemic circulation and the specific sites where it can exert its
biological action [53]. Even though a compound has strong
antioxidant or other biological activities in vitro, it would have little
biological activity in vivo if insufficient or none of the compound
reaches the target tissues. The most abundant polyphenols in our
diet are not necessarily those that have the best bioavailability
profile. Only a small part of the dietary ACNs are absorbed, an d
large amounts of the ingested compounds are likely to enter the
colon. Until now, ACNs have been thought to have a very low
bioavailability, in fact human pharmacokinetic studies generally
identified less than 1% of the ingested parent ACNs in biological
fluids, despite the consumption of doses exceeding 500 mg [54].
This percentage is lower than that found for other flavonoids [55].
However, it is to underline that spontaneous degradation of ACNs
to phenolic acids and aldehydes has been reported to occur under
experimental [56] and biological conditions [34, 50]. The
incongruity between bioavailability and reported bioactivity has
undoubtedly hindered the field of ACN research, and future
research into ACNs bioactivity should include their degradation
products. In particular, it has been shown that, at physiological pH
such as in the bloodstream, Cyanidin-3-Glucoside (C3G), the most
abundant ACN in food, easily degrades to cyanidin, that rapidly and
spontaneously degrades to PCA, which can be further metabolized
to glucuronide and sulphate conjugates [47]. Furthermore, Wang et
al. [57] have demonstrated that C3G is intensively transformed into
PCA in apoE-deficient mice, and that the plasma maximal level of
C3G is 3.7-fold lower than that of PCA. In human, PCA accounts
for 44.4% of the ingested C3G in 6-h post-consumption
bloodstream [34]. A mean concentration of PCA of 2.0 nmol/g has
been found in fecal samples collected the day after pigmented
orange juice consumption, thus suggesting that the in vivo
production of PCA by human colon microflora occurs [34, 58].
Finally, studies carried out in rats and in perfused rat heart have
shown that PCA may further be converted to vanillic acid [59].
However, to establish conclusive evidence for the effectiveness
of a dietary compound in disease prevention and human health
improvement, it is essential to know its bioavailability but also to
evaluate its biological activity in target tissues.
In a recent study [60] seventy-two human subjects consuming
moderate amounts of berry for 8 weeks in a randomized dietary
intervention trial, have shown increased plasma PCA levels (+21%)
with respect to the control group. In another randomized, cross-over
study [61], 375 ml of Champagne wine or a control matched
beverage have been administered to 15 healthy human volunteers.
The consumption of Champagne wine induced an increase in
urinary excretion of a number of phenolic metabolite, among which
PCA, compared with the control intervention. Finally, an interesting
study has demonstrated that male Balb/cA mice fed a standard diet
supplemented with PCA for 12 weeks showed increased PCA
deposit in plasma and tissues such as brain, heart, liver, and kidneys
[62].
ANTIOXIDANT ACTIVITY
Oxidative stress plays a pivotal role in the pathogenesis of
several degenerative diseases such as atherosclerosis,
cardiovascular diseases, type 2 diabetes, neurodegenerative
diseases, and cancer. Furthermore, the ‘free radical theory of
ageing’ casts lights on understanding the process of ageing, and in
Fig. (2). Gastrointestinal metabolism and absorpt ion of polyphenols. In the stomach oligomeric polyphenols dissociate into monomers. In the small
intestine a few of the polyphenol glycosides are hydrolysed to aglycons. In the colon polyphenols undergo substantial structural modifications by colonic
microflora resulting in the formation of metabolites such as phenolic acids. Most of the conjugation process takes place in the liver. The conjugation, that
mainly includes methylation, sulfation, and glucuronidation, represents a metabolic detoxication process that facilitates the biliary and urinary excretion of the
polyphenols by increasing their hydrophilicity.
Monomeric
units
Oligomeric
polyphenols
Stomach
Small Intestine
jejunum
ileum
Colon
Liver
Phenolicacids
glucuronides
Kidney
Urine
Omethylated
Sulphates
Portal
vein
Further
metabolism
Renal excretion
ofglucuronides
Oligomers
cleaved cells
SKINAND
BRAIN
Gutmicroflora
Flavonoids
Polyphenols
glucuronides
2904 Current Medicinal Chemistry, 2012 Vol. 19, No. 18 Masella et al.
finding effective anti-ageing agents [63-67]. The reactive oxygen
species (ROS) are continuously produced within the cell,
particularly during mitochondrial electron transport chain, and in
peroxisomes [68]. Furthermore, ROS can be generated as a
consequence of foreign compounds, toxins, drugs and foods, or
exposure to environmental factors such as pollutants, heavy metals
or ultraviolet radiations [69]. Notably, at low physiological levels,
ROS function as ‘redox messengers’ in intracellular signaling and
regulation [70], whereas excess of ROS induces oxidative
modification of cellular macromolecules, which leads to aberrant
cell functions causing membrane and DNA damage, enzyme
inactivation and, ultimately, cell death [71]. Controlling the
intracellular redox state by means of efficient antioxidant
machinery represents thus a crucial event in the prevention of cell
damage, and it is easily understandable why humans have
developed sophisticated mechanisms to cope with an excess of free
radical production. Endogenous enzymatic and non-enzymatic
antioxidant defenses, and exogenous antioxidants supplied by the
diet play a pivotal role in such protective mechanisms.
A central role in the endogenous defense system is played by
glutathione (GSH), a ubiquitous cysteine-containing tripeptide that
participates in redox reactions by the reversible oxidation of its
active thiol group (GSSG) [72]. GSH scavenges directly free
radicals or act as an enzymatic substrate for antioxidant/detoxifying
enzymes including glutathione peroxidase (GPx) and glutathione-S-
transferases (GST), which are involved in the detoxification/
reduction of H2O2, lipid hydroperoxides and electrophilic
compounds. In the presence of oxidative stress the ratio
GSH/GSSG rapidly decreases. The produced GSSG can be reduced
by glutathione reductase (GR) [73]. In addition, GSH can be de
novo synthesized by the glutathione synthase complex [74]. The
efficiency of the entire GSH cycle depends on the functionality of
GSH-related enzymes and the availability of amino acids (Fig. 3).
Among the endogenous non-enzymatic antioxidant defenses, it
should be mentioned uric acid which is the most concentrated
antioxidant in human blood [75]. Uric acid is an intermediate
product of purine metabolism. It cannot scavenge superoxide, but
does act against peroxynitrite, peroxides, and hypoclorous acid
[76]. However, the presence of ascorbic acid in plasma is required
for the antioxidant effects of uric acid [77].
Nutritional antioxidants, among which plant polyphenols, have
been considered pivotal in determining the risk of disease because
of their capability of counteracting oxidative stress. Plant
polyphenols are multifunctional as they act as reducing agents,
hydrogen donating antioxidants, and singlet oxygen quenchers. In
some cases metal chelation properties have been demonstrated. The
chemical properties of polyphenols, in terms of availability of the
phenolic hydrogens as hydrogen donating radical scavengers,
predict their antioxidant activity in vitro. Actually, the effective in
vivo antioxidant potential of dietary polyphenols depends on several
factors such as quantities consumed, absorbed and/or metabolized,
plasma and/or tissue concentrations, type and content of single
polyphenol, and, finally, synergistic effects. However, the chemical
structure of phenolic compounds differently affects all the factors
described above. For instance, a glycosylated anthocyanin shows
lower radical-scavenging activity than the correspondent aglycone,
as the glycosylation reduces the ability of the anthocyanin radical to
delocalize electrons. Fukumoto & Mazza [78] have reported that
the antioxidant activity of anthocyanidins increase with the number
of hydroxyl groups in the molecule, and decrease with
glycosylation process.
Furthermore, strong evidence has been provided for an indirect
antioxidant activity of polyphenols exerted by activating the
endogenous defense system. In this regard, a number of studies
have shown that the consumption of food reach in polyphenols,
such as red wine, spinach, strawberries, black and green tea, and
wheat bran, is associated with a significant plasma antioxidant
capacity (PAC) enhancement [79-81], which seems to be associated
mainly to the increase of uric and ascorbic acids in plasm a [82, 83].
However, it has recently been demonstrated th at ascorbic acid an d
Fig. (3). GSH and related enzymes. Reduced glutathione (GSH) is the substrate for glutathione peroxidases (GPx) and glutathione transferases (GST) during
the detoxification of hydrogen peroxide, lipid hydroperoxides, and electrophilic compounds. During GST-mediated reactions, GSH is conjugated with various
electrophiles, and the GSH adducts formed are actively secreted by the cell. During GPx mediated reaction oxidized glutathione (GSSG) is formed. Since
GSSG is highly toxic for the cell, it is in part extruded from the cells and in part back-reduced to GSH by glutathione reductase (GR) utilizing NADPH as
reductant. The resulting depletion of cellular GSH is replaced by de novo synthesis through two sequential ATP-dependent reactions catalyzed by -
glutamylcysteine synthetase (-GCS),– the rate-limiting enzyme – and glutathione synthetase.
Glutamate Cysteine Glycine
J
-GCS
GSH H2O2
Hydroperoxides
H2O
Hydroxy compounds
GSSG
GPx
GR
NADP+
NADPH
Toxic
compounds
GST
GSH-adducts
out
in
Protocatechuic Acid and Human Disease Prevention Current Medicinal Chemistry, 2012 Vol. 19, No. 18 2905
urate levels do not significantly change from the baseline after
polyphenol consumption suggesting that the enhanced PAC is most
likely caused by phenolics [84]. In addition, several experimental
data indicate a tight interrelation between GSH and its related
enzymes, and dietary polyphenols. Actually, the strengthening of
the cellular antioxidant defense system by specific nutrients can
represent a central event in determining the fate of the cells since
the depletion of host antioxidant defenses contributes to sub-
cellular damage and cytotoxicity. In general, the increased
vulnerability of th e cells to the assault of free radical in an
inflammatory environment results in mitochondrial and DNA
damage until apoptosis in several tissues, which might lead to
multiple o rgan failure.
Antioxidant Activity of PCA
Hydroxybenzoic acid derivatives exhibit potent antioxidant
activities. In particular, catechol-type o-diphenols such as PCA and
its esters, show high antiradical activity towards 2,2-diphenyl-1-
picrylhydrazyl (DPPH) in vitro [85,86], as they are readily
converted to the corresponding o-quinones and further complex
products [87,88] (Fig. 4). The molecular structure of PCA indicates
that it possesses potent antioxidant and anti-radical activities [85]
due to the number of phenolic hydroxyl group present in PCA
molecule. However, PCA esters have higher antioxidant activity
than PCA likely because of the higher lipophilicity, which is a main
factor in counteracting lipoperoxidation [89, 90]. It has been
demonstrated that the radical scavenging activities of PCA and its
esters depend on the solvent used [91, 92]. In non-alcoholic acetone
or acetonitrile PCA and its esters consume two radicals and are
converted to the corresponding quinones. In contrast, in methanol
or ethanol PCA esters rapidly scavenge more than four radicals
with a concomitant conversion to the corresponding quinone-3-
hemiacetals and the production of alcohol adducts at C2 (Fig. 4)
[93]. In particular, the regeneration of catechol structures by the
nucleophilic addition of a solvent alcohol molecule on o-quinones
is a key reaction responsible for the higher radical scavenging
activity of PCA esters in alcoholic solvents than in non-alcoholic
solvents [91]. Notably, the radical scavenging activity is greatly
affected by the C-1 substituent on the catechol ring [94]. Studies
carried out in several cell models have confirmed the effectiveness
of PCA in counteracting lipoperoxidation and oxidative stress
mediated by hydrogen peroxides and oxidized lipids [95-100]. For
the sake of information it has to be taken in account that high
concentrations of PCA, as for other antioxidants, could exert pro-
oxidant activities, thus favoring toxic effects and tissue damages. A
few studies have been specifically addressed to clarify this aspect
showing that PCA (500mg/Kg) intraperitoneal administered to mice
induces depletion of GSH content and, consequently, liver, kidney,
and skin damages [101]. A growing body of evidence has
demonstrated a close relationship between PCA and the
endogenous antioxidant defenses that might be the principal
responsible for the antioxidant activity of PCA in biological
systems. It is worthy of note that the efficiency of the antioxidant
defense system is reduced in degenerative diseases and ageing
process; for instance, the activities of SOD, catalase, and the
enzymes of GSH cycle have been demon strated to be reduced in
plasma of patients with ageing brain disorders [102]. Interestingly,
PCA purified from Alpinia oxyphylla extracts dose-dependently
balances the endogenous antioxidant system by increasing the
activity of GPx, SOD, and catalase, consequently reducing lipid
peroxidative damage in rat pheochromocytoma cell line PC12
[103], as well as in spleen and liver of aged rats injected intra-
peritoneal with different doses of PCA for 7 days [104]. Notably,
PCA administered to aged rats improves rat cognitive function by
attenuating ageing alterations [96].
Many studies in different cell models have demonstrated that
PCA prevents the d ecrease in GSH levels in the presence of an
oxidant such as oxidized LDL (oxLDL), and increases the basal
level of intracellular GSH [100, 105]. This might be the result of
GSH sparing due to the antioxidant activity of PCA that substitutes
GSH in scavenging radicals. However, it might be related to the
ability of PCA in strengthening the activity of the entire GSH-cycle
by improving the efficiency of GSH-related enzymes. At this
regard, it has been shown that PCA can directly activate mRNA
transcription and activity of antioxidant/detoxifying enzymes such
as GPx and GR in murine macrophages [105].
It is well known that the transcriptional activation of
antioxidant/detoxifying enzyme genes is regulated by common
upstream regulatory elements called AREs, or antioxidant response
elements, present in the promoter region of those genes [106].
There is a fair amount of evidence that ARE sequences regulate the
cellular defense system, being in turn strictly regulated by
transcrip tional factors such as the nuclear factor erythroid 2 (NF-
E2)-related factor 2 (Nrf2), a member of the cap'n'collar family of
basic leucine zipper transcription factors ubiquitously expressed
[107]. Under homeostatic conditions, Kelch lik e ECH-associated
protein 1 (Keap1) sequesters Nrf2 in the cytoplasm by forming
heterodimers [108]. The intracellular level of ROS regulates gene
expression by modulating various signaling pathways and
transcription factors including Nrf2 [107, 109, 110]. A major
mechanism for Nrf2 activation is phosphorylation due to several
kinases such as mitogen-activated protein kinases (MAPKs),
protein kinase C (PKC) and phosphatidylinositol 3-kinases (PI3K)
[111-113]. Phosphorylated Nrf2 is more stable and has a reduced
binding affinity toward Keap 1; consequently it can translocate into
the nucleus where it binds to the ARE sequences of target genes
inducing the expression of the majority of detoxifying/antioxidant
enzymes [114]. ARE sequences have recently been demonstrated in
the promoter region of GPx and GR [115,116]. Polyphenols have
been demonstrated to induce ARE-dependent antioxidant genes by
activating Nrf2 (Fig. 5) [72, 117]. Recently, we have provided
scientific evidence of the molecular mechanism responsible for the
modulation of mRNA expression of antioxidant enzymes by PCA
in macrophages [118]. PCA induces the increase of Nrf2 mRNA
expression and, mainly, a strong increase in Nrf2 phosphorylation
mediated by JNK, which allows the transcription factor to escape
degradation, translocate into the nucleus, and bind the specific ARE
sequences present in GPx and GR promoters. Taken together these
findings support the concept that PCA, as well as several other
polyphenols, improves antioxidant cellular defenses in critical
CO
2
R
OH
OH
-2H
+
-2 .
(DPPH)
CO
2
R
O
O
MeOH
CO
2
R
O
OH
OMe
R=H Protocatechuic acid
R=Me Methyl protacatechuate
R=H Protocatechuic quinone
R=Me Protocatechuic quinone methyl ester
R=H Protocatechuic quinone methyl hemiacetal
R=Me Protocatechuic quinone methyl hemiacetal methyl ester
Fig. (4). Chemical structures of protocatechuic acid and its derivatives.
2906 Current Medicinal Chemistry, 2012 Vol. 19, No. 18 Masella et al.
target cells, such as macrophages, whose dysfunction has been
implicated in many patho-physiological processes that entail
inflammation and atherogenesis [119-120].
Fig. (5). PCA up-regulates antioxidant/detoxifying enzyme expressions.
PCA directly activates mRNA transcription of antioxidant/detoxifying
enzymes through antioxidant responsive elements (AREs). PCA might
influence the pathways that regulate ARE activation by i) modifying the
capability of Kelch like ECH-associated protein 1(Keap1) in sequestering
nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), ii) activating
Mitogen-activated protein kinases (MAPK) involved in Nrf2 stabilization,
and/or iii) directly affecting Nrf2 binding to AREs.
ANTI-INFLAMMATORY ACTIVITY
Oxidative stress and inflammatory processes seem to jointly
contribute to the pathophysiology of almost all chronic-
degenerative diseases. The generation of ROS as well as of reactive
nitrogen species (RNS) is able to activate redox sensitive
transcription factors that induce the expression of pro-inflammatory
molecules leading to a state of chronic inflammation. On the other
hand, inflammation itself might contribute to ROS and RNS
generation amplifying the damages in target cells and organs.
Inflammatory process represents a protective response occurring in
tissues as a consequence of any insult with the aim of destroying or
diluting the cause of cell injury with no detriment to the host [121].
As described by Celsus, rubor (redness), tumor (swelling), dolor
(pain), and calor (heat) are the symptomatic manifestations of
complex tissue responses to harmful stimuli. Briefly, inflammation
is a reaction of the microcirculation that is characterized by the
movement of serum proteins and leukocytes (neutrophils,
eosinophils and macrophages) from the blood to the extra-vascular
tissue, and by the activation of cell- and plasma-derived
inflammatory mediators. The inflammato ry process is regulated by
coordinated activation of different signaling pathways that
modulate the expression of both pro- and anti-inflammatory
mediators in resident tissue cells (such as fibroblasts, endothelial
cells, tissue macrophages, and mast cells), and recruit leucocytes
[122,123]. From a more actual point of view, inflammation
represents an important process for the maintenance of biological
homeostasis [121]. However, uncontrolled inflammation might be
potentially harmful and may represent a main pathogenetic
mechanism for many diseases [123]. Indeed, the inability to self-
limiting inflammatory response leads to prolonged activation of
pro-inflammatory mediators responsible for ongoing tissue injury
and organ dysfunction. As a consequence, chronic inflammation
plays a critical role in the pathophysiology of the major chronic
diseases including obesity, cardiovascular disease (CVD), type 2
diabetes (T2D), Alzheimer’s disease (AD) and many types of
cancer [121,124,125].
PCA and Inflammation
A relationship between nutrition and the immune system does
exist, as well as a link between nutrition and chronic diseases [126].
It is thus not surprising that huge efforts and resources have been
focused on the understanding of how dietary nutrients might impact
pharmacological targets of inflammation. In addition, since several
synthetic drugs provide unknown side effects, there has been a need
for new and safe anti-inflammatory agents. Various phyto-
chemicals, including phenolic compounds, have shown anti-
inflammatory activity in vitro and in vivo. Many data have
suggested that polyphenols can work as modifiers of signal
transduction pathways to elicit their beneficial effects [127-129].
Targeting these inflammatory regulators by using food components
may be a useful strategy to prevent or to ameliorate the
development of chronic inflammation-related diseases; PCA
appears to be a good candidate since recent studies have suggested
that ACNs and PCA might exert important anti-inflammatory
activities [98,130,131].
A large number of mediators, including nitric oxide, lipid
mediators, cytokines/chemokines, adhesion molecules, and matrix
metalloproteinases (MMPs), are involved in the initiation,
maintenance, and resolution of inflammatory process [132,133].
PCA and Nitric Oxide
Mediators such as histamine and nitric oxide (NO) are potent
vasodilatators that propagate and amplify the inflammatory
response. NO is ex-novo synthesized by endothelial (eNOS),
neuronal (nNOS), and inducible (iNOS) nitric oxide synthases.
Both lack and excess of NO production appear to have important
implications in chronic diseases [134-136]. In fact, while a
significant increase in NO -iNOS-produced- participates in
provoking inflammatory process [137], a low NO bioavailability –
eNOS produced- is central to the development and maintenance of
hypertension and related endothelial dysfunction [138].
Consequently, the inhibition of excessive inducible NO production
may be an anti-inflammatory therapeutic target, and the protection
against a decrease in constitutive NO production in the vasculature
may prevent the development of atherosclerosis and endothelial
dysfunction [135, 139]. PCA appears to significantly reduce iNOS
protein expression and NO production both in vitro and in vivo.
Specifically, PCA reduces NO production and iNOS expression in a
dose-dependent manner in LPS-treated RAW 264.7 cells [130]. The
PCA pre-treatment of CCl(4)-treated rat results in the reduction of
iNOS expression in liver, and NO levels in plasma [98]. Finally, the
topical application of PCA on mouse epidermis, counteracts the
increase in iNOS protein level and the nitrite production induced by
12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse skin [140].
PCA and Lipid Mediators
Lipid mediators such as arachidonic acid-derived prostanoids
and leukotrienes, as well as oxidized phospholipids and platelet-
activating factors (PAF), are potent pro-inflammatory mediators
[141]. Prostaglandin E2 (PGE2), prostaglandin I2 , and tromboxane
A2 are produced by cyclooxygenases (COXs) which exist in two
major isoforms (COX-1 and COX-2) and one variant (COX-3).
COX-1 is constitutively expressed in many tissues, whereas COX-2
is expressed in inflammation-related cells (i.e., macrophages,
monocytes, neutrophils, fibroblasts) in response to various stimuli
ARE/EpRE
Nucleus
Nrf 2
P
Keap1
Nrf 2
P
Nrf 2 Keap1
PCA
PCA
PCA
Nrf 2
MAPK
cascade
MAPK cascade
Protocatechuic Acid and Human Disease Prevention Current Medicinal Chemistry, 2012 Vol. 19, No. 18 2907
[142]. Lipoxygenases are the enzyme responsible for generating
hydroxyl acids, and leukotrienes B4 and C4.
Oxidized phospholipids (OxPLs) are generated when LDL and
cellular phospholipids containing polyunsaturated fatty acids
(PUFA) undergo oxidative attack. Accumulating data demonstrate
that OxPLs are formed in vivo in a variety of pathological
situations, and play an important role in atherosclerosis. However,
the large number of different OxPLs identified makes difficult to
elucidate their contribution to the pathology [141]. PAF is one of
the most potent phospholipid with atherogenic effects being
implicated in many inflammatory actions including monocytes
activation and infiltration [143,144]. The inhibition of lipid
mediator generating enzymes is one of the PCA anti-inflammatory
mechanisms. PCA inhibits COX-2 and PGE2 expression both in
vitro in LPS-treated RAW264.7 cells and in vivo in mice treated
with carrageenan, a polysaccharide that induces inflammation
[130]. The over-expression of COX-2 in Sprague-Dawley treated
with CCl4 is significantly reduced by the pre-treatment with PCA
[98]. Similarly, pre-treatment w ith PCA diminishes the dramatic
increase of COX-2 protein expression and activity, induced by TPA
in mouse skin, by approximately 50% [140].
Furthermore, in vitro experiments have demonstrated that PCA,
as well as other polyphenols, is able to inhibit LDL oxidation
[145,146].
PCA and Cytokines/Chemokines
Cytokines, produced by both resident and migrating cells, are
the major mediators of intercellular communications required for an
integrated response to a variety of stimuli in immune and
inflammatory processes [147,148]. A distinct group of cytokines,
called chemokines, which include IL-8, monocyte chemoattractant
protein (MCP)-1, and macrophage inflammatory proteins (MIP),
has shown the ability to recruit and activate leukocytes at the site of
inflammation [149]. Thus, the imbalance between pro-
inflammatory (i.e. IL-1, IL-2, TNF, Il-6, IL-8 and IFN-) and
anti-inflammatory cytokines (i.e. IL-10, IL-4, TGF) might
determine the outcome of disease, both on the short- and long-term
basis [127,148]. In addition, TNF and IL-1 interact with
endothelial cells to produce adhesion molecules, such as
intracellular adhesion molecule (ICAM)-1, vascular adhesion
molecule (VCAM)-1, and E-selectin, that allow inflammatio n
progression and exacerbate the severity of clinical disorders [149-
153]. Notably, IL-1 has recently b een shown to exert auto crine
action on monocytes and to influence redox balance and glutathione
levels [144]. Targeting cytokine/chemokine system with plant-
derived compounds represents thus an important and alternative
approach for the treatment of inflammatory diseases [127, 154].
Notably, the pre-treatment of mouse aortic endothelial cells with
PCA inhibited the cytokine-induced expression of ICAM-1 and
VCAM-1 [131].
PCA and the Complement System
The complement system orchestrates immunological and
inflammatory processes, extending far beyond simple elimination
of danger. It consists of a number of small proteins found in the
blood, normally circulating as inactive precursors that initiate and
amplify a cascade of further activations when stimulated by one of
several triggers [155]. The effects of complement are normally
beneficial to the host, but they can also cause adverse effects
depending on the site, extent, and duration of activation. AD is
associated with neuroinflammation, and up-to-date works provide
evidence of complement activation, localized with both fibrillar
amyloid- (A) plaques and tangles [124, 156]. Thus it appears
very hopeful a recent report demonstrating that compounds, among
which PCA extracted from black colored rice bran can exert anti-
complement activity against the classical complement pathway
[157].
PCA, Nuclear Factor-
B, and MAPKs
Among a huge number of pro-inflammatory mediators nuclear
factor-B (NF-B) and MAPKs are the principal effectors that,
directly or indirectly, regulate inflammatory responses [158-160].
In particular, the inhibitor B (IB) kinase (IKK)/NF-B signaling
pathway regulates genes involved in many aspects of the
inflammatory response, and has been implicated in the pathogenesis
of several inflammatory diseases [161]. Increased activation of NF-
B has often been detected in both immune and non-immune cells
in tissues affected by chronic inflammation, where it is believed to
exert detrimental functions by inducing the expression of pro-
inflammatory mediators that orchestrate and sustain the
inflammation [162].
NF-B is a dimer that classically consists of a p50 subunit and a
trans-activating subunit p65 (or relA). In un-stimulated cells, NF-
B is sequestered in the cytoplasm as an inactive non-DNA-binding
form associated with the inhibitory proteins IBs [163]. Upon cell
stimulation with various NF-B inducers, IBs are rapidly
phosphorylated by IKK complex on two serine residues, which
targets th e inhibitor protein for ubiquitination and subsequent
degradation by the ubiquitin-proteasome pathway. As a
consequence, the translocation of NF-B to the nucleus is
facilitated, as well as the binding to specific DN A sites and the
induction of a wide range of genes encoding pro-inflammatory
cytokines (e.g., IL-1, IL-2, IL-6, and TNF), chemokin es (e.g., IL-
8, MIP-1 and MCP-1), adhesion molecules (e.g., ICAM, VCAM,
and E-selectin), acute-phase proteins, immuno-receptors, growth
factors, and inducible enzymes such as COX-2, MMPs, and iNOS
[159]. The critical role of NF-B in pro-inflammatory gene
expression has generated an enormous effort to develop specific
inhibitors for the treatment of chronic inflammation [164, 165]. It is
worthy of note that PCA treatment inhibits, in a dose-dependent
manner, the TNF-induced expression and activation of NF-B
(p65) in mouse aortic endothelial cells [131]. A similar effect has
been described for PCA extracted from black rice and used to treat
LPS-induced RAW 264.7 cells. Specifically, this agent inhibits
LPS-induced IB d egradation and NF-B activation as well as the
translocation of p65 subunit into the nucleus [130]. The pre-
treatmen t with PCA has b een described to decrease NF-B p65-
DNA binding and to inhibit the TPA-induced IKK activity,
consequently reducing COX-2 activity and iNOS expression, in
mouse skin [140]. Interestingly, it has been demonstrated that PCA
specifically inhibits the nuclear translocation of NF-B, but not of
other nuclear transcription factors such as AP-1, in human gastric
carcinoma cells [166] (Fig. 6).
The MAPK cascades are intracellular signal transduction
pathways that respond to changes in the cellular environment, and
constitutive upstream regulators of transcription factor activities
that control a large number of fundamental cellular processes
including inflammation, cell growth, proliferation, death and
differentiation [158]. Mammals express at least four distinctly
regulated groups of MAPKs, namely the extracellular signal-related
kinases (ERK)-1/2, the c-Jun amino-terminal kinases (JNK1/2/3),
the p38 kinases (, , , and ) and the ERK5. The MAPKs are
activated by specific MAPK kinases (MAPKK s) that, in turn, can
be activated by different MAPKK kinases (MAPKKKs), increasing
the complexity of the MAPK pathways. MAPKs are activated in
response to diverse arrays of extracellular stimuli, and mediate
signal transduction from the cell surface to the nucleus. Mitogens
and growth factors frequently activate the ERK1/2 route, while
stress and inflammation constitute the main triggers for the JNK
and p38 cascades, sometimes referred as ‘stress activated protein
kinases’ [167]. Increased activity of MAPKs and their involvement
in the regulation of the synthesis of inflammation mediators make
them potential targets for novel anti-inflammatory therapeutics
[127, 167, 168]. Notably, PCA might exert potent anti-
inflammatory effects by regulating MAPK activation (Fig. 6). A
2908 Current Medicinal Chemistry, 2012 Vol. 19, No. 18 Masella et al.
recent work has shown that PCA counteracts the LPS-stimulated
phosphorylation of ERK1/2, JNK1/2, and p38 MAPKs in RAW
264.7 cells. In fact, LPS stimulates the activation of all three
MAPK pathways whereas PCA inhibits the activation of p38, ERK
and JNK pathways [130].
In conclusion, few studies have demonstrated that PCA presents
important anti-inflammatory actions because of the ability to inhibit
the synthesis and/or activity of most inflammatory mediators and
regulatory pathways. However, it is worth of note that, in vivo
studies, besides those in vitro, have suggested the potential utility of
PCA in reducing the severity of inflammatory response that takes
part in many chronic diseases. In particular, PCA supplied to
streptozotocin (STZ)-induced diabetic mice substantially decreases
inflammatory cytokine levels in kidney and heart, and consequently
plasma levels of C reactive protein (CRP) and von Willebrand
factor. In addition, in the same organs, PCA markedly d ecreases
MCP-1 levels. These findings strongly suggest that PCA might be a
potent agent against diabetic-asso ciated cardiac and renal
inflammatory injuries [169]. The same suggestion comes from two
other studies. One of these has shown that PCA pre-treatment
couples the inhibitory action on plasma TNF levels with the
enhancement of IL-10 release in LPS/D-galactosamine-treated
mouse [170]. The other one has showed that PCA diminishes
inflammatory stress by lowering the level of IL-1, IL -6, TNF,
and MCP-1 in the liver of mice fed a trans-fatty acid-rich diet, and
thus it could be considered a potent agent for alleviating hepatic
steatosis as well [171].
Min et al. have found that oral administration of black rice,
C3G, or PCA once a day for three days before carrageenan
injection into subcutaneous air pouches, protects male BALB/c
mice from in flammation. In fact, the carrageenan-induced increases
in inflam matory markers, such as TNF, IL-1, and PGE2, as well
as in COX-2 expression, and NF-B and MAPK activation, are
potently inhibited by all the tested polyphenols, being PCA the
most potent inhibitor [130].
However, for the completeness of information, we have to point
out that other studies have reported opposite effects of PCA [172];
this discrepancy might be due to the dosage of PCA and the cell
type used.
PCA, Atherosclerosis and CVD
It is well known that atherosclerosis is a multistep, chronic,
inflammatory process associated with a disorder of lipid
metabolism. Taken together the alterations in both lipid metabolism
and immune responses in macrophages play a significant role in
promoting the development of atherosclerotic lesions [173]. It has
been demonstrated that PCA is able to influence various events
involved in the pathogenesis of atherosclerosis, especially because
of its antioxidant and anti-inflammatory properties. First of all,
PCA exerted a powerful protective activity against vessel damage
by counteracting a major initiating event, i.e. the oxidation of LDL
by macrophage cells, considered to be responsible for early
vascular damages [105]. PCA inhibited LDL oxidation induced by
the macrophage-like cell line J774 A.1likely by the up-regulation of
GPx and GR expressions and activities, thus ameliorating the entire
functionality of GSH system [174]. A typical sign of the early stage
of atherosclerosis is the infiltration of circulating monocytes into
the vascular wall [175]; this process is modulated by a number of
chemokines and their receptors [176]. Notably, PCA treatment, at
physiological order of concentrations, attenuates the expression of
CCR2 in PBMC isolated from apo-E-deficient mice, which leads to
a functional consequence. More importantly, orally administered
PCA reduces macrophage infiltration into the abdominal cavity of
the mice [57]. Furthermore, PCA administration in apo-E-deficient
mice is able to reduce aortic and plasma VCAM-1 and ICAM-1
expressions, as well as NF-B activity, consequently inhibiting the
formation of the early atherosclerotic lesions. In addition, in the
same animal model, PCA supplementation reduces cholesterol
accumulation in aortas by 50%, without modifying the plasma lipid
profile [131]. This finding might indicate that the beneficial effect
of PCA on the cardiovascular system is mainly due to its anti-
inflammatory prop erties. A crucial event in the progression of
atherosclerotic plaque, as well as in the increase of inflammatory
process, is the occurrence of apoptosis (see below). In particular, in
Fig. (6). Schematic representation of potential points of action of PCA within the infla mmatory cascade. PCA might exert anti-inflammatory activities
by acting at different levels of the inflammatory process. PCA a) counteracts inflammatory mediators, b) inhibits the progression of inflammation by
modulating different signal transduction pathways, c) modifies the activity of transcription factors and, consequently, the expression of specific genes.
Mitogen-activated protein kinases (MAPK), MAPK-kinase (MAPKK); MAPK kinase kinase (MAPKKK); p50-RelA (NF-B); nuclear factor erythroid 2 (NF-
E2)-related factor 2 (Nrf2). Inhibition =; activation = .
inflammatory cytokines,
stress, aging, oxidative stress,
genotoxic agents
Maf
RelA
p50 Nrf2
transcription
Cytokines, transcription factors,
adhesion molecules
Nucleus
ARE system and cellular
defense enzymes
MAPKKKs
MAPKKs
MAPKs
PCA
a
b
b
b
c
c
Protocatechuic Acid and Human Disease Prevention Current Medicinal Chemistry, 2012 Vol. 19, No. 18 2909
advanced atherosclerotic plaques, up to 50% of the apoptotic cells
are macrophages, which may promote core expansion and plaque
instability. In advanced human atheroma the defective phagocytic
clearance of dead macrophages leads to plaque necrosis, which
triggers acute atherothrombotic vascular events [177]. We have
studied the properties of PCA to counteract oxLDL mediated
cytotoxic and pro-apoptotic activity in murine macrophages. Worth
of note, the treatment with PCA inhibits the apoptosis occurrence in
macrophages not only by counteracting oxidative stress, but also by
specifically modulating intracellular signaling pathways responsible
for caspase activation [178]. Furthermore, anti-thrombotic activity
of ACNs and colonic metabolites, mainly exerted through the
inhibition of platelet functions, has been demonstrated [179].
Anti-Hyp erglicemic Activity o f PCA
Maintenance of glucose homeostasis by strict hormonal control
is of utmost importance to human physiology. Failure of this
control, with defects in both insulin action and insulin secretion,
can result in the metabolic syndrome, a multi-symptom disorder of
energy homeostasis. The disturbance of glucose metabolism is often
related to the increase of fat mass, especially in the abdominal area,
which, in turn, results in inflammation, exacerbated oxidative stress
at the whole body level with increased circulating oxLDL levels
and malfunction in several organs including adipose tissue [180,
181]. Insulin resistance seems to underlie the early stages of the
development of the metabolic syndrome, and thus approaches to
improve insulin action have been, and remain, key targets for
slowing or ultimately preventing type 2 diabetes [182, 183]. The
potential of polyphenols in controlling glycemia is currently under
intensive study, and indications for positive effects of AC Ns on
glucose homeostasis have been obtained in vitro and in an imal
studies [184-187]. In particular, some compelling studies have
reported that ACNs improve insulin sensitivity and glucose uptake
in diabetic rats [186]. Notably, Harini et al. [188], have
demonstrated that PCA adm inistered orally to STZ-diabetic rats for
45 days prevents the increase in plasma glucose and glycosylated
hemoglobin, and the decrease in plasma insulin and hemoglobin. In
addition, PCA normalizes the activities of gluconeogenic enzymes
like glucose 6-phosphatase and fructose 1,6-bisphosphatase, as well
as that of the glycolytic enzyme glucokinase. Worth of note, PCA
does not induce significant effects in normal rats. Thus, PCA might
exert a potential antihyperglycemic effect that is comparable with
that obtained with classical antidiabetic drugs such as
glibenclamide. In addition, PCA reverts the alterations of lipid
profile associated with STZ-induced diabetes in rats [189]. In STZ-
diabetic mice, Lin et al. [189] have demonstrated that dietary
supplementation with PCA improves glycemic control and
attenuates homeostatic disorder. Furthermore, they have found that
orally administered PCA reduces the hyperglycemia-induced
advanced glycation end-products (AGEs) both in plasma and in
organs such as kidney [62]. This is of great importance since the
accumulation of AGEs leads to organ deterioration, and favors the
development of diabetic complications [190]. This antiglycative
activity of PCA might be related to the attenuation of oxidative and
inflammatory stresses [169]; however, the authors have also found
that PCA diminishes the renal activity and expression of aldose
reductase and sorbitol dehydrogenase, both involved in AGE
production. Interestingly, the authors have provided possible
molecular mechanisms for PCA action. First of all they have found
that PCA diminishes the mRNA expression and activity of PKC-
and PKC-, and, consequently, of TGF1 that, in turn, promotes
ECM formation and tissue fibrosis. Secondly, PCA reverts the
down-regulation of PPAR and, particularly, of PPAR, that is a
principal metabolic regulator of glucose and lipid metabolism, the
most extensively studied and clinically validated gene for
therapeutic utility in type 2 diabetes, and a main target for many
antidiabetic drugs such as thiazolidinediones (TZDs) [191, 192].
Indeed P PAR is a target of insulin activity, and regulates the
expression and activity of key players in the maintenance of
glucose transport machinery efficiency, such as glucose transporter
(GLUT) 4 and adiponectin. Very recently we have demonstrated
that PCA is able to increase the glucose uptake and to enhance
GLUT4 translocation and adiponectin secretion in human primary
omental adipocytes [193]. This insulin-like activity, probably
caused by the increased activity of PPAR induced by PCA, might
offer interesting possibility in diabetes care. In fact, new ligands for
PPAR that do not procure the unwanted side-effects shown by
many insulin-sensitizing agents, e.g. TZDs, are being sought.
ANTIAPOPTOTIC/PROAPOPTOTIC ACTIVITY
Polyphenols can improve cell survival and protect against
cytotoxicity by inhibiting apoptosis, but also they can induce
apoptosis and prevent tumor growth [194, 195]; these opposite
effects are mainly due to the control of cell redox state. In fact,
acting as antioxidants or pro-oxidants, these compounds behave as
anti-apoptotic or pro-apoptotic agents, respectively. Since the
modulation of cell apoptosis is one of the main mechanisms
responsible for the protective action against degenerative
pathologies, polyphenols have been proposed as therapeutic agents
against cancer, neurodegenerativ e diseases, and cardiovascular
diseases [196, 197].
Apoptosis is a genetically controlled and evolutionarily
conserved form of cell death of critical importance for the normal
embryonic development and for the maintenance of tissue
homeostasis in the adult organism. Apoptosis is mediated by two
main pathways that, although strictly intertwined, represent
different ways to reach the same result, i.e. the death of a cell via
caspase activation (Fig. 7).
The extrinsic, or death receptor, pathway is activated when a
specific ligand, such as Fas ligand, binds its corresponding death
receptor, such as Fas receptor, on the cell surface. This induces a
cascade of events leading to the formation of a supramolecular
complex called death-inducing signaling complex (DISC), which
results in the cleav age of inactive pro caspases-8 to the active
caspase-8. Caspase-8, in turn, triggers a series of reaction
eventually affecting the mitochondrial membrane potential, thus
interacting with the intrinsic pathway [195].
The intrinsic, or mitochondrial, pathway is activated by
different agents which all induce ROS overproduction and the onset
of oxidative stress. Activation of the intrinsic pathway is
accompanied by mitochondria membrane potential collapse and
cytochrome c translocation from the mitochondrial inter-membrane
space into the cytoplasm. Cytochrome c, and several pro-apoptotic
factors (Apaf-1, dATP), bind procaspase-9 to form the
‘apoptosome’ complex that activates caspase-9 through
autocatalysis. Both caspase-9 and caspase-8 cleave pro caspase-3
generating the active form of caspase-3 that, in turn, activates other
executor caspases, cleaves cyto skeletal, and activates specific
DNase. The activation of caspases is regulated by several factors
[195] including MAPKs and the tumor suppressor protein p53. The
activation of p53 is affected by ROS, and regulates, positively or
negatively, the transcription of dozen downstream effector genes
such as BAX, a member of the Bcl-2 family of proteins, and p66Sh,
an oxidative stress sensor protein, that promote the opening of the
mitochondrial permeability transition pore and trigger apoptosis
[198]. Furthermore, p53 modulates the balance between pro- and
anti-apoptotic proteins belonging to Bcl-2 family. MAPKs and the
isoform of PKC control the cellular level and nuclear
accumulation of p53 [95, 103, 199-201]. Among MAPKs, ERKs
have been associated with the regulation of cell proliferation. In
contrast, the activation of JNK and p38 kinases is controlled by
stress signaling and has been associated with the induction of
apoptosis.
2910 Current Medicinal Chemistry, 2012 Vol. 19, No. 18 Masella et al.
In conclusion, apoptosis represents a very complex process
whose modulation depends on many players differently regulating
crucial intracellular events. Consequently, these facto rs represent
suitable targets for focused interventions.
Several in vitro and in vivo studies have demonstrated that
PCA, as other polyphenols, can exert pro-oxidant/anti-oxidant and
pro-apoptotic/anti-apoptotic effects as well.
Anti-Apoptotic Effects of PCA
It has been found by Zhou-Stache [201] that PCA, isolated from
Salvia mitorrhizam, inhibits TNF-induced cell death of human
umbilical vein endothelial cells (HUVECs) and Jurkat cells. PCA,
isolated from th e kernels of Alpinia oxyphylla, stimulates cell
proliferation and markedly attenuates mitochondrial dysfunction by
inhibiting the loss of mitochondrial membrane potential, the
formation of ROS, the GSH depletion, the activation of caspase-3,
and the down-regulation of Bcl-2 [95,103,202,203]. In another
study carried out in PC12 cells, the protective effects of PCA on
H2O2-induced has been investigated. Authors showed that PCA
increases PC12 viability and markedly reduces apoptotic cell death
in a dose-dependent manner. In these cells, the levels of GSH and
the activity of catalase increase, while GPx activity remains
unchanged, suggesting that PCA acts mainly as antioxidant [204].
This hypothesis has been confirmed by Tarozzi et al. [205] that
have demonstrated the ability of cyanidin and PCA, but not of C3G,
to inhibit mitochondrial function loss and DNA fragmentation. The
potential protective effects of compounds generated during in vivo
metabolism of ACNs has been the topic of comparative studies on
the effects of different compounds in the human neuroblastoma cell
line SH-SY5Y. C3G, cyanidin, and PCA inhibit H2O2-induced ROS
formation, but at different cellular levels: C3G at membrane level,
PCA at cytosolic level, and cyanidin at both levels. In addition,
cyanidin shows a higher antioxidant activity at membrane and
cytosolic level than C3G and PCA, respectively.
Taken in account all these findings that demonstrate the
anticytotoxic and anti-apoptotic activities of PCA, it becomes clear
that PCA might have interesting application in the prevention and
treatment of chronic-degenerative diseases. The effects of PCA in
preventing neurodegenerative diseases, such as Parkinson’s disease,
have been extensively studied in PC12 cell model. Parkinson's
disease is characterized by the progressive degeneration of
dopaminergic neurons in substantia nigra with the presence of -
synuclein inclusions termed Lewy bodies. It has been demonstrated
in vitro that PCA inhibits cytotoxicity, apoptotic morphology,
reduction of tyrosine hydroxylase expression, and abnormal
oligomerization of -synuclein in PC12 cells treated with1-methyl-
4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) [206]. In an in vivo
study, the same group has demonstrated that PCA inhibits the
reduction of the latent periods in a rotarod test, and the contents of
dopamine and its metabolites in striatum as well. Furthermore, PCA
counteracts the decreased expression of tyrosine hydroxylase in
substantia nigra of C57BL/6J mice induced by MPTP [207].
The A peptide aggregation into oligomeric and fibrillar species
affects neuronal viability, having a causal role in the development
of AD. PCA isolated from Smilacis chinae rhizome has been found
to prevent A (25-35)-induced neurotoxicity in cultured rat cortical
Fig. (7). Apoptosis pathways. The extrinsic pathway is triggered by members of the death receptor superfamily such as Fas. Binding of Fas ligand (Fas-L) to
Fas induces trimerization of the receptor, recruitment of specific adaptor proteins (FADD) and procaspase 8 molecules. The multi-molecular complex (DISC)
results in the activation of caspase-8. Active caspase-8 can, in turn, activate Bid, a pro-apoptotic member of Bcl-2 family of proteins.
Oxidants, toxicants, drugs or ionizing radiation, which all induce ROS overproduction, can activate the intrinsic pathway (right). The intrinsic or mitochondrial
pathway is also triggered by DNA damage and ROS overproduction via p53 activities. The death stimuli result in loss of mitochon drial membrane integrity
and release of cythocrome c, apoptotic protease activating factor 1 (Apaf-1) and other pro-apoptotic factors in the cytoplasm. Maintenance or perturbation of
mitochondrial membrane potential depends on the ratio between pro-apoptotic (Bax) and anti-apoptotic (Bcl-2) members of Bcl-2 family, causing or
preventing cythocrome c release. Multiple molecules of cythocrome c, Apaf-1, dATP and procaspase-9 associate to form a supramolecular complex termed
apoptosome, that activates caspase-9 through autocatalysis. Both the activated caspase-9 and caspase-8 cleave procaspase-3 generating the active caspase-3
that, in turn, activates other executor caspases and cleaves cellular targets. Procaspase cleavage and caspase activities are tightly controlled by several factors
such as the Inhibitors of Apoptosis Protein (IAPs) family.
D
D
ROS
Oxidants, Toxicants,
Drugs, Ionizing radiations
DNA DAMAGE
FasL
Fas/CD95
FADD
Cytochrome C
Cellular
Tar ge t s
Cellular
Tar ge t s
Procaspase 8
DISC
IAPs
c-FLIP
Bcl-2
D
BID
Bax
p53
p66Shc
Death Receptor pathway Mitochondrial pathway
Procaspase 3
Apaf-1
Procaspase 9
Apoptosome
Apaf-1
Target genes
Caspase 9
Caspase 3
Caspase 8
Protocatechuic Acid and Human Disease Prevention Current Medicinal Chemistry, 2012 Vol. 19, No. 18 2911
neurons by interfering with the increase of [Ca(2+)], and by
inhibiting glutamate release, generation of ROS and caspase-3
activity [208]. However, C3G, but not PCA, might protect and
rescue the neuronal cells from toxicity induced by A (1-42), by
inhibiting its spontaneous aggregation in human neuronal SH-
SY5Y cells [205]. A recent study has been aimed at investigating
the protective effects exerted by PCA against apoptosis induced by
oxidized lipids in intestinal Caco-2 cells [100]. We have found that
PCA fully counteracts the oxidized lipid-induced redox imbalance
by inhibiting ROS overproduction, GSH depletion, and the
impairment of SOD, catalase and GPx. Furthermore, the oxidized
lipids induce a dramatic increase in p66Shc expression that
irreversibly lead to cells apoptosis by mitochondrial depolarization,
and caspase-9 and caspase-3 activation. These effects are fully
counteracted by PCA that blocks the cascade of intracellular signals
responsible for the over-expression and rearrangement of p66Shc.
These results suggest that the anti-apoptotic effect of dietary
polyphenols might represent an intestinal protecting mechanism
able to neutralize dietary oxidant-induced intestinal damage. In fact,
although the bioavailability of the polyphenols is a limiting factor
in the majority of the body districts, dietary polyphenols
concentrate in th eir active forms in the intestinal lumen because of
the enzymatic activities of enterocytes and colon bacteria. This
could result in a more pronounced protective activity on the
intestinal mucosa, and, thus, in a highly effective prevention of
damages induced by diet oxidant.
PCA as Growth Inducer
The protective activity exerted by PCA against cytotoxicity
might be due not only to the anti-apoptotic activity, but also to the
capability of stimulating cell proliferation and growth. Recently, it
has been reported that PC A is able to increase cultu red neural stem
cells (NSC) viability and to stimulate cell proliferation in a dose-
and time-dependent manner [203]. This finding might strongly
support the hypothesis that PCA is a good candidate for the
treatment of neurodegenerative diseases. Indeed, NCS isolated from
embryonic brain are a heterogeneous population of multipotential
cells recently reported to exist also in the adult nervous system, in
particular in the hippocampus and in the subventricular zone. Worth
of note, it has been shown that NCS from hippocampus have the
potential for differentiating to functional neurons, which indicates
them as candidate targets for stimulating neurogenesis in
neurodegenerative diseases [209]. Notably, pharmacokinetics
studies have demonstrated that PCA readily permeates the blood
brain barrier after oral administration in rats [210].
Similar results have been obtained in human adipose tissue-
derived stromal cells [211]. The authors have demonstrated that the
cell cycle progresses from the G0/G1 phase to the S phase after
treatment with PCA, and the cells retain their functional
characteristics of multipotential mesenchymal progenitors.
Interestingly, the PCA-induced cell proliferation depends on the
over-expression of cyclin D1.
Pro-Apoptotic Activity of PCA
Besides the anti-apoptotic effects reported above, PCA has been
demonstrated to exert also a strong pro-apoptotic activity, which
might be relevant to some pathological conditions such as cancer.
This opposite behavior is likely related to environmental conditions.
Indeed, although polyphenols have been considered as antioxidant
agents, they can be pro-oxidant in certain circumstances such as in
cancer cells. Cancer cells constitutively generate large, but
tolerable, amounts of ROS [212]. As described above, polyphenols,
by acting as anti-oxidants, can contribute to counteract oxidative
stress occurrence, consequently suppressing the oxidative stress-
responsive genes and the proliferation of cancer cells. On the other
hand, polyphenols can induce ROS hyper-production determining
an intolerable lev el of oxidative stress in cancer cells that are thus
irreparably damaged and undergo apoptosis. Since apoptosis
eliminates genetically damaged cells or cells that may be
inappropriately induced to proliferate, it represents a protective
mechanism against neoplastic transformation and development of
tumors.
This dual-effect of PCA and other polyphenols has been
investigated in the human leukemia cells HL-60 [213],
demonstrating that PCA, apigenin, or bisabolol show an anti-
genotoxic effect by counteracting H2O2 and also exhibit tumoricidal
activity by inducing apoptosis. However, the pro-apoptotic activity
could be due to the ability to modulate oxidative stress as well as to
a direct action on regulatory proteins and signaling pathways, that
exert their regulatory effect in determining cell fate [214]. In the
study of Tseng et al. [215] PCA, isolated from the dried flower of
Hibiscus sabdariffa L. (Malvaceae), has been found to inhibit the
survival of human promyelocytic leukemia HL-60 cells in a
concentration- and time-dependent manner. The study has revealed
that HL-60 cells undergo internucleosomal DNA fragmentation and
morphological changes characteristic of apoptosis after a 9-hr
treatment with 2 mM PCA. Moreover, PCA treatment causes an
increase in the level of hypo-phosphorylated retinoblastoma protein
(RB) and, on the contrary, a decline in hyper-phosphorylated RB. A
rapid loss of RB has been observed when the treatment period is
extended. Furthermore, PCA application dramatically reduces Bcl-2
and increases BAX expressions. The authors conclude that the
reduction of RB phosphorylation and Bcl-2 protein may play a
crucial role in the pro-apoptotic induction exerted by PCA.
It has been demonstrated that antioxidant and antitumo r
activities of Rhus Verniciflua Stokes (RVS), used as a food additive
and a traditional herbal medicine, is closely associated with th e
polyphenol content. The purified polyphenol extract strongly
suppresses the proliferative capability of B lymphoma cells by
inducing apoptosis with DNA fragmentation, low fluorescence
intensity in the nuclei after propidium iodide staining, and
appearance of DNA laddering. In particular, the authors have
identified PCA, fustin, fisetin, sulfuretin, and butein, as the main
active compounds responsible for the antioxidant and
antiproliferative activities of RVS extract [216]. The same purified
extract inhibits growth and induces apoptosis in human
osteosarcoma (HOS) cells by activating caspase-8, modifying the
balance between BAX and Bcl-2, and inducing the release of
cytochrome c. Furthermore, PARP cleavage is closely associated
with the induction of apoptosis in HOS cells [217].
An interesting study by Stagos et al. [218] has been addressed
to investigate th e mechanisms by which g rape ex tracts and
individual polyphenols contained in those extract (caffeic acid,
ferulic acid, gallic acid, PCA, and rutin) exert their
chemopreventive and antitumor activities in cancer cells. The grape
extracts, the polyphenol-rich fractions, and individual polyphenols,
among which PCA, have been shown to be potent inhibitors of
topoisomerase I (topo I), indicating that the inhibition of this
enzyme might be one of the mechanisms accounting for the
anticancer and chemopreventive activity. Moreover, the grape
extracts inhibit the mitomycin C-induced DNA strand breakage
suggesting that they could prevent ROS-mediated DNA damage.
On the contrary, the polyphenol-rich fractions and the individual
polyphenols enhance the mitomycin C-induced DNA strand
breakage indicating a pro-oxidant activity that lead to the
enhancement of DNA damage and might account for the cytotoxic
and pro-apoptotic properties of these compounds towards cancer
cells. The anticancer activity of PCA has also been studied in
human gastric adenocarcinoma (AGS) cells, by analyzing in detail
the signaling pathways involved [219]. Molecular data have shown
that the effects of PCA in these cells might be mediated via
sustained phosphorylation and activation of JNK and p38 MAPK,
but not of ERK. In fact, either the treatment with pharmacological
2912 Current Medicinal Chemistry, 2012 Vol. 19, No. 18 Masella et al.
inhibitors or the transfection with the mutant p38 or/and JNK
expression vectors reduces the JNK/p38 MAPK-related protein
phosphorylation and expression, and eventually the PCA-mediated
apoptosis. Similar results have been obtained in HepG2 cells where
PCA, but not chlorogenic acid or luteolin, dose-dependently and
specifically stimulate JNK and p38 activities [220].
Szaefer et al. [221] have demonstrated that PCA, as well as
other phenolic acids, may affect TPA-induced tumor promotion and
inflammation in female Swiss mice by inhibiting specific isoforms
of PKC, which is considered a major intracellular recepto r for th e
mouse skin tumor promoter TPA. Pre-incubation with Nok-1
monoclonal antibody, which is inhibitory to Fas signaling,
interferes with PCA-induced cleavage of pro-caspase and
sensitization to anti-Fas receptor-induced apoptosis. These results
suggest that the multiple signaling pathways from the MAPK to the
subsequent mitochondria- and/or Fas-mediated caspase activation
might be potential requirements for PCA-induced apoptosis. Yin,
M.C. et al. [222] have examined the apoptotic effects of PCA at
micromolar concentrations on human breast cancer MCF7, lung
cancer A549, HepG2, cervix HeLa, and prostate cancer LNCaP
cells. PCA treatment causes strong apoptotic effects in these cancer
cells by increasing DNA fragmentation, decreasing mitochondrial
membrane potential, lowering Na
+
-K
+
-ATPase activity, and
elevating caspase-3 and caspase-8 activities.
Finally, it should be highlighted that PCA exerts cytotoxic
effects ag ainst hepatocellular carcinoma cells, whereas it protects
primary hepatocytes against cytotoxicity [220,223]. These findings
further support the hypothesis that PCA is likely to be a useful
chemotherapeutic agent, without harmful effects on normal cells,
since it shows a higher selectivity towards cancerous cells than to
normal human cells.
PCA, and Metastasis Development
It has recently been described the potential ability of PCA to
interfere with the metastasis development. The metastatic p rocess
consists of different steps such as tumor cell detachment, lo cal
invasion, migration, angiogenesis, vessel invasion, and adhesion to
endothelial cells, extravasation, and growth in other organs. When
cancer cells invade normal tissues, degradation of the extracellular
matrix (ECM), migration and proliferation of malignant cells occur.
These ev ents are accompanied by several cell alteration s, including
the over-expression of proteolytic enzyme activities, such as
MMPs, especially MMP-2 and MMP-9. In this regard, phenolic
acids, including PCA, have been shown to exert strong anticancer
activity by inhibiting cell migration and reducing metastatic power
of AGS cells, most likely because of the down-regulation of
PI3K/AkT/small GTPase signals that inhibit NF-B, MMP-2, and
MMP-9 activities [224]. Furthermore, in different cancer cell lines,
PCA also inhibits the production of the vascular endothelial growth
factor (VEGF), a signal protein that contribute to cancer growth and
dissemination when over-expressed [222].
Lin et al. [166] have used B16/F10 mouse melanoma cells,
widely used as model system in studying metastasis, to inject
C57/BL6 mice orally treated with PCA for 6 weeks. Interestingly,
the treatment with PCA reduces the number of metastatic nodules,
the volume of hepatocellular tumors, and the weight of liver
compared with the untreated animals. The authors also
demonstrated that the down-regulation of the Ras/Akt/NF-B
signaling pathway is responsible for the inhibitory effects of PCA.
The inhibition of this pathway is considered a promising approach
in cancer treatment, because it is involved in cell migration and
invasiveness, most likely by the up-regulation of MMP-2, which
degrades the ECM. According to this hypothesis, the same study
shown that PCA inhibits MMP-2 secretion in AGS cells.
Furthermore, PCA decreases the migration of the cells in a dose-
and time-dependent manner probably by inhibiting NF-B nuclear
translocation.
ANTI-MICROBIAL ACTIVITY OF PCA
Polyphenols, including PCA, exert antimicrobial activity, which
represents an interesting field of application both in health
protection and in food preservation in order to avoid food-borne
illnesses [225-227]. Furthermore, the in vitro antimicrobial activity
of natural compounds could provide useful information for
developing novel antibiotics. Medicinal plants could be used as a
possible way to treat diseases caused by multidrug-resistan t bacteria
[228,229]. The antimicrobial activity of purified flavonoids may
result in susceptibility differences against species with different
origins and background [225]. PCA has been shown to be active
against both Gram-negative and Gram-positive strains, including
E.Coli, Ps. Aeruginosa, S. Aureus, B. cereus, and Enterobacteria
[230-232] Notably, PCA, as well as other phytochemicals, interacts
synergistically with selected antibiotics against Ps. aeruginosa, that
is a major nosocomial pathogen resistant to many antibacterial
drugs and particularly dangerous to immune-depressed population.
PCA used in combination with antibiotics increases th e
susceptibility of the pathogen to the drugs and reduces drug toxicity
in vitro [230,232,233].
Finally, PCA, as well as diallyl disulphide and diallyl
trisulphide, exhibited in vitro inhibitory effects against the growth
of susceptible, drug-resistant, H. pylori in broth and mouse stomach
homogenate. This finding indicates that PCA might be useful in the
prevention or therapy of H. pylori that is implicated in peptic ulcer,
duodenal ulcer and gastric cancer [234].
CONCLUSION
A growing body of evidence provides new insight in the
comprehension of the cellular and molecular mechanisms
responsible for the potential preventive/therapeutic activity of PCA
against a number of human diseases. The experimental data suggest
a multifaceted action of PCA through the modulation of cell redox
environment and signals and biochemical pathways involved in the
control of inflammation and oxidative stress. Consequently, PCA
modulates the balance between cell survival and cell death.
Notably, PCA can exert opposite effects depending on the
concentration, the cell system, and the type or stage of th e
degenerative process. It is worth mentioning that PCA seems to
specifically behavior as a chemotherapeutic agent, without harmful
effects on normal cells. However, much evidence of such properties
has been collected from cellular and animal studies, while clinical
studies are still lacking. Although the in vitro systems represent a
useful tool for unraveling the mechanisms of action that allow the
identification of the specific molecular targets, data obtained in
vitro may not be physiologically relevant. This means that further
studies and clinical trials are needed to fully establish the
preventive and therapeutic effectiveness of PCA, and to prove its
safety in humans.
CONFLICT OF INTERESTS
None of the authors have conflict of interest.
ACKNOWLEDGEMENTS
This work was partially supported by Italy/USA cooperation
program (Targeted Research Project no. 11US/23)
REFERENCES
[1] Arts, I. C.; Hollman, P. C. Polyphenols and disease risk in epidemiologic
studies. Am. J. Clin. Nutr., 2005, 81(1), 317S-325S.
[2] Williamson, G.; Manach, C. Bioavailability and bioefficacy of polyphenols
in humans. II. Review of 93 intervention studies. Am. J. Clin. Nutr.,2005,
81(1), 243S-255S.
Protocatechuic Acid and Human Disease Prevention Current Medicinal Chemistry, 2012 Vol. 19, No. 18 2913
[3] U.S. Department of Agriculture (USDA). U.S. Department of Health and
Human Services. Dietary Guidelines for Americans 2005. Food Groups to
Encourage.
http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter5.ht
m (Accessed July 28, 2008).
[4] Cheynier, V. Polyphenols in foods are more complex than often thought.
Am. J. Clin. N utr., 2005, 81(1 Suppl), 223S-229S.
[5] Rababah, T. M.; Ereifej, K. I.; Esoh, R. B.; Al-u'datt, M. H.; Alrababah, M.
A.; Yang, W. Antioxidant activities, total phenolics and HPLC analyses of
the phenolic compounds of extracts from common Mediterranean plants.
Nat. Prod. Res., 2011, 25(6), 596-605.
[6] Rodrigues, R. B.; Lichtenthaler, R.; Zimmermann, B. F.; Papagiannopoulos,
M.; Fabricius, H.; Marx, F.; Maia, J. G.; Almeida, O. Total oxid ant
scavenging capacity of Euterpe oleracea Mart. (acai) seeds and identification
of their polyphenolic compounds. J. Agric. Food Chem., 2006, 54(12), 4162-
7.
[7] Jayaprakasha, G. K.; Ohnishi-Kameyama, M.; Ono, H.; Yoshida, M.;
Jaganmohan Rao, L. Phenolic constituents in the fruits of Cinnamomum
zeylanicum and their antioxidant activity. J. Agric. Food Chem., 2006, 54(5),
1672-9.
[8] Loots, D. T.; van der Westhuizen, F. H.; Jerling, J. Polyphenol composition
and antioxidant activity of Kei-apple (Dovyalis caffra) juice. J. Agric. Food
Chem., 2006, 54(4), 1271-6.
[9] Rodrig uez Madrera, R.; Picinelli Lobo, A.; Suarez Valles, B. Phenolic profile
of Asturian (Spain) natural cider. J. Agric. Food Chem., 2006, 54(1), 120-4.
[10] Fang, Z.; Zhang, M.; Tao, G.; Sun, Y.; Sun, J. Chemical compo sition of
clarified bayberry (Myrica rubra Sieb. et Zucc.) juice sediment. J. Agric.
Food Chem., 2006, 54(20), 7710-6.
[11] Nuntanakorn, P.; Jiang, B.; Einbond, L. S.; Yang, H.; Kronenberg, F.;
Weinstein, I. B.; Kennelly, E. J. Polyphenolic constituents of Actaea
racemosa. J. Nat. Prod., 2006, 69(3), 314-8.
[12] Sanz, M.; Cadahia, E.; Esteruelas, E.; Munoz, A. M.; Fernandez De Simon,
B.; Hernandez, T.; Estrella, I. Phenolic comp ounds in cherry (Prunus avium)
heartwood with a view to their use in cooperage. J. Agric. Food Chem.,2010,
58(8), 4907-14.
[13] Zhang, H.; Jiang, L.; Ye, S.; Ye, Y.; Ren, F. Systematic evaluation of
antioxidant capacities of the ethanolic extract of different tissues of jujube
(Ziziphus jujuba Mill.) from China. Food Chem. Toxicol., 2011, 48(6), 1461-
5.
[14] Ao, C.; Higa, T.; Ming, H.; Ding, Y. T.; Tawata, S. Isolation and
identification of antioxidant and hyaluronidase inhibitory compounds from
Ficus microcarpa L. fil. bark. J. Enzyme Inhib. Med. Chem., 2010, 25(3),
406-13.
[15] Beevi, S. S.; Narasu, M. L.; Gowda, B. B. Polyphenolics profile, antioxidant
and radical scavenging activity of leaves and stem of Raphanus sativus L.
Plant Foods Hum. Nutr., 2010, 65(1), 8-17.
[16] Barros, L.; Duenas, M.; Ferreir a, I. C.; Baptista, P.; Santos-Buelga, C.
Phenolic acids determination by HPLC-DAD-ESI/MS in sixteen different
Portuguese wild mushrooms species. Food Chem. Toxicol., 2009, 47(6),
1076-9.
[17] Zhong, G. X.; Li, P.; Zeng, L. J.; Guan, J.; Li, D. Q.; Li, S. P. Chemical
characteristics of Salvia miltiorrhiza (Danshen) collected from different
locations in China. J. Agric. Food Chem., 2009, 57(15), 6879-87.
[18] Wu, X.; Pittman Iii, H. E.; Hager, T.; Hager, A.; Howard, L.; Prior, R. L .
Phenolic acids in black raspberry and in the gastrointestinal tract of pigs
following ingestion of black raspberry. Mol. Nutr. Food Res., 2009, 53(Suppl
1), S76-84.
[19] Chin, Y. W.; Chai, H. B.; Keller, W. J.; Kinghorn, A. D. Lignans and other
constituents of the fruits of Eu terpe oleracea (Acai) with antioxidant and
cytoprotective activities. J. Agric. Food Chem., 2008, 56(17), 7759-64.
[20] Ma, Y. Q.; Ye, X. Q.; Fang, Z. X.; Chen, J. C.; Xu, G. H.; Liu, D. H.
Phenolic compounds and antioxidant activity of extracts from ultrasonic
treatment of Satsuma Mandarin (Citrus unshiu Marc.) peels. J. Agric. Food
Chem., 2008, 56(14), 5682-90.
[21] Pacheco-Palencia, L. A.; Mertens-Talcott, S.; Talcott, S. T. Chemical
composition, antioxidant properties, and th ermal stability of a phytochemical
enriched oil from Acai (Euterpe oleracea Mart.). J. Agric. Food Chem., 2008,
56(12), 4631-6.
[22] Slimestad, R.; Fossen, T.; Vagen, I. M. Onions: a source of unique dietary
flavonoids. J. Agric. Food Chem., 2007, 55(25), 10067-80.
[23] Chan, K. C.; Ho, H. H.; Huang, C. N.; Lin, M. C.; Chen, H. M.; Wang, C. J.
Mulberry leaf extract inhibits vascular smooth muscle cell migratio n
involving a block of small GTPase and Akt/NF-kappaB signals. J. Agric.
Food Chem., 2009, 57(19), 9147-53.
[24] Ramadan, M. A.; Ahmad, A. S.; Nafady, A. M.; Mansour, A. I. Chemical
composition of the stem bark and leaves of Ficus pandurata Hance. Nat.
Prod. Res., 2009, 23(13), 1218-30.
[25] Kwak , J. H.; Kim, H. J.; Lee, K. H.; Kang, S. C.; Zee, O. P. Antioxidative
iridoid glycosides and phenolic compounds from Veronica peregrina. Arch.
Pharm. Res., 2009, 32(2), 207-13.
[26] Ekiert, H.; Szewczyk, A.; Kus, A. Free phenolic acids in Ruta graveolens L.
in vitro culture. Pharmazie, 2009, 64(10), 694-6.
[27] Arimboor, R.; Kumar, K. S.; Arumughan, C. Simultaneous estimation of
phenolic acids in sea buckthorn (Hippophae rhamnoides) using RP-HPLC
with DAD. J .Pharm. Biomed. Anal., 2008, 47(1), 31-8.
[28] Ayinde, B. A.; Onwukaeme, D. N.; Omogbai, E. K. Isolation and
characterization of two phenolic compounds from the stem bark of Musanga
cecropioides R. Brown (Moraceae). Acta Pol. Pharm., 2007, 64(2), 183-5.
[29] Ajila, C. M.; Jaganmohan Rao, L.; Prasada Rao, U. J. Characterization of
bioactive compounds from raw and ripe Mangifera indica L. peel extracts.
Food Chem. Toxicol., 2010, 48(12),3406-11.
[30] Sanz, M.; Cadahia, E.; Esteruelas, E.; Munoz, A. M.; Fernandez de Simon,
B.; Hernandez, T.; Estrella, I. Phenolic compounds in chestnut (Castanea
sativa Mill.) heartwood. Effect of toasting at cooperage. J. Agric. Food
Chem., 2010, 58(17), 9631-40.
[31] Waterhouse, A. L. Wine phenolics. Ann. N. Y. Acad. Sci., 2002, 957, 21-36.
[32] D'Archivio, M.; Filesi, C.; Vari, R.; Scazzocchio, B.; Masella, R.
Bioavailability of the polyphenols: status and controversies. Int. J. Mol. Sci.,
2011, 11(4), 1321-42.
[33] Carrasco-Pancorbo, A.; Cerretani, L.; Bendini, A.; Segura-Carretero, A.;
Gallina-Toschi, T.; Fernandez-Gutierrez, A. Analytical determination of
polyphenols in olive oils. Journal of Separation Science, 2005, 28(9-10),
837-858.
[34] Vitaglione, P.; Donnarumma, G.; Napolitano, A.; Galvano, F.; Gallo, A.;
Scalfi, L.; Fogliano, V. Protocatechuic acid is the major human metabolite of
cyanidin-glucosides. J. Nutr., 2007, 137(9), 2043-8.
[35] Mazza, G.; Miniati, E. Anthocyanins in fruits, vegetables, and g rains. CRC
Press. Boca Raton, Florida, USA, 1991.
[36] Giov annini, C.; Vari, R.; Scazzocchio, B.; Sanchez, M.; Santangelo, C.;
Filesi, C.; D'Archivio, M.; Masella, R. OxLDL induced p53-dependent
apoptosis by activating p38MAPK and PKCdelta signaling pathways in
J774A.1 macrophage cells. J. Mol. Cell. Biol., 2011, 3(5), 316-8.
[37] Felgines, C.; Texier, O.; Besson, C.; Lyan, B.; Lamaison, J.L.; Scalbert ,
A.Strawberry pelargonidin glycosides are excr eted in urine as intact
glycosides and glucuronidated pelargonidin derivatives in rats. Br. J. Nutr.,
2007, 98(6),1126-31.
[38] Gonthier, M. P.; Donovan, J. L.; Texier, O.; Felgines, C.; Remesy, C.;
Scalbert, A. Metabolism of dietary procyanidins in rats. Free Radic. Biol.
Med., 2003, 35(8), 837-44.
[39] Tsuda, T.; Horio, F.; Osawa, T. Absorption and metabolism of cyanidin 3-O-
beta-D-glucoside in rats. FEBS Lett., 1999, 449(2-3), 179-82.
[40] Galv ano, F.; Vitaglione, P.; Li Volti, G.; Di Giacomo, C.; Gazzolo, D.;
Vanella, L.; La Fauci, L.; Fogliano, V. Protocatechuic acid: the missing
human cyanidins' metabolite. Mol. Nutr. Food Res., 2008, 52(3), 386-7;
author reply 388.
[41] Wu, X.; Beecher, G. R.; Holden, J. M.; Haytowitz, D. B.; Gebh ardt, S. E.;
Prior, R. L. Concentrations of anthocyanins in common foods in the United
States and estimation of normal consumption. J. Agric. Food Chem., 2006,
54(11), 4069-75.
[42] Chun, O. K.; Chung, S. J.; Song, W. O. Estimated dietary flavonoid intake
and major food sources of U.S. adults. J. Nutr., 2007, 137(5), 1244-52.
[43] Havsteen, B. H. The biochemistry and medical significance of the
flavonoids. Pharmacol. Ther., 2002, 96(2-3), 67-202.
[44] Hertog, M. G.; Hollman, P. C.; Katan, M. B.; Kromhout, D. Intake of
potentially anticarcinogenic flavonoids and their determinants in adults in
The Netherlands. Nutr. Cancer, 1993, 20(1), 21-9.
[45] Kay, C. D.; Mazza, G.; Holub, B. J.; Wang, J. Anthocyanin metabolites in
human urine and serum. Br. J. Nutr., 2004, 91(6), 933-42.
[46] Kay, C. D.; Mazza, G. J.; Holub, B. J. Anthocyan ins exist in the circulation
primarily as metabolites in adult men. J. Nutr., 2005, 135(11), 2582-8.
[47] Kay, C. D.; Kroon, P. A.; Cassidy, A. The bioactivity of dietary anthocyanins
is likely to be mediated by their degradation products. Mol. Nutr. Food Res.,
2009, 53(Suppl 1), S92-101.
[48] Day, A. J.; Canada, F. J.; Diaz, J. C.; Kroon, P. A.; McLauchlan, R.; Faulds,
C. B.; Plumb, G. W.; Morgan, M. R.; Williamson, G. Dietary flavonoid and
isoflavone glycosides are hydrolysed by the lactase site of lactase phlorizin
hydrolase. FEBS Lett., 2000, 468(2-3), 166-70.
[49] Gee, J. M.; DuPont, M. S.; Day, A. J.; Plumb, G. W.; Williamson, G.;
Johnson, I. T. Intestinal transport of quercetin glycosides in rats involves
both deglycosylation and interaction with the hexose transport pathway. J.
Nutr., 2000, 130(11), 2765-71.
[50] Aura, A. M.; Martin-Lopez, P.; O'Leary, K. A.; Williamson, G.; Oksman-
Caldentey, K. M.; Poutanen, K.; Santos-Buelga, C. In vitro metabolism of
anthocyanins by human gut microflora. Eur J. Nutr., 2005, 44(3), 133-42.
[51] Kuhnau, J. The flavonoids. A class of semi-essential food components: their
role in human nutrition. World Rev. Nutr. Diet., 1976, 24, 117-91.
[52] Del Rio, D.; Costa, L. G.; Lean, M. E.; Crozier, A. Polyphenols and health:
What compounds are involved? Nutr. Metab. Cardiovasc. Dis., 2010, 20(1),
1-6.
[53] Porrini, M.; Riso, P. Factors influencing the bioavailability of antioxidants in
foods: a critical appraisal. Nutr. Metab. Cardiovasc. Dis., 2008, 18(10), 647-
50.
[54] Kay, C. D. Aspects of anthocyanin absorption, metabolism and
pharmacokinetics in humans. Nutr. Res. Rev., 2006, 19(1), 137-46.
[55] Manach, C.; Williamson, G.; Morand, C.; Scalbert, A.; Remesy, C.
Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97
bioavailability studies. Am. J. Clin. Nut r., 2005, 81(1 Suppl), 230S-242S.
[56] Sadilova, E.; Stintzing, F. C.; Carle, R. Anthocyanins, colour and antioxidant
properties of eggplant (Solanum melongena L.) and violet pepper (Capsicum
annuum L.) peel extracts. Z. Naturforsch C., 2006, 61(7-8), 527-35.
2914 Current Medicinal Chemistry, 2012 Vol. 19, No. 18 Masella et al.
[57] Wang, D.; Zou, T.; Yang, Y.; Yan, X.; Ling, W. Cyanidin-3-O-beta-
glucoside with the aid of its metabolite protocatechuic acid, reduces
monocyte infiltration in apolipoprotein E-deficient mice. Biochem.
Pharmacol., 2011, 82(7), 713-9.
[58] Gao, K.; Xu, A.; Krul, C.; Venema, K.; Liu, Y.; Niu, Y.; Lu, J.; Bensoussan,
L.; Seeram, N. P.; Heber, D.; Henning, S. M. Of the major phenolic acids
formed during human microbial fermentation of tea, citrus, and soy flavonoid
supplements, only 3,4-dihydroxyphenylacetic acid has antiproliferative
activity. J. Nutr., 2006, 136(1), 52-7.
[59] Cao, Y. G.; Zhang, L.; Ma, C.; Chang, B. B.; Chen, Y. C.; Tang, Y. Q.; Liu,
X. D.; Liu, X. Q. Metabolism of protocatechuic acid influences fatty acid
oxidation in rat heart: new anti-angina mechanism implication. Biochem.
Pharmacol., 2009, 77(6), 1096-104.
[60] Koli, R.; Erlund, I.; Jula, A.; Marniemi, J.; Mattila, P.; Alfthan, G.
Bioavailability of various polyphenols from a diet containing moderate
amounts of berries. J. Agric. Food Chem., 2010, 58(7), 3927-32.
[61] Vauzour, D.; Houseman, E. J.; George, T. W.; Corona, G.; Garnotel, R.;
Jackson, K. G.; Sellier, C.; Giller y, P.; Kennedy, O. B.; Lovegrove, J. A.;
Spencer, J. P. Moderate Champagne consumption promotes an acute
improvement in acute endothelial-independent vascular function in healthy
human vo lunteers. Br. J. Nu tr., 2010, 103(8), 1168-78.
[62] Lin, C. Y.; Tsai, S. J.; Huang, C. S.; Yin, M. C. Antiglycative effects of
protocatechuic acid in the kidneys of diabetic mice. J. Agric. Food Chem.,
2011, 59(9), 5117-24.
[63] de Moura, M. B.; dos Santos, L. S.; Van Houten, B. Mitochondrial
dysfunction in neurodegenerative diseases and cancer. Environ. Mol.
Mutagen., 2010, 51(5), 391-405.
[64] Patten, D. A.; Germain, M.; Kelly, M. A.; Slack, R. S. Reactive oxygen
species: stuck in the middle of neurodegeneration. J. Alzheimers Dis., 2010,
20(2), S357-67.
[65] Queen, B. L.; Tollefsbol, T. O. Polyphenols and aging. Curr. Aging Sci.,
2010, 3(1), 34-42.
[66] Kan eto, H.; Katakami, N.; Matsuhisa, M.; Matsuoka, T. A. Role of reactive
oxygen species in the progression of type 2 diabetes and atherosclerosis.
Mediators Inflamm., 2010, 453892.
[67] Victo r, V. M.; Apostolova, N.; Herance, R.; Hernandez-Mijares, A.; Rocha,
M. Oxidative stress and mitochondrial dysfunction in atherosclerosis:
mitochondria-targeted antioxidants as potential therapy. Curr. Med. Chem.,
2009, 16(35), 4654-67.
[68] Cadenas, E.; Sies, H. Oxidative stress: excited oxygen species and enzyme
activity. Adv. Enzyme Regul., 1985, 23, 217-37.
[69] Hanukoglu, I. Antioxidant protective mechanisms against reactive oxygen
species (ROS) generated by mitochondrial P450 systems in steroidogenic
cells. Drug . Metab. Re v., 2006, 38(1-2), 171-96.
[70] Han, D.; Ybanez, M. D.; Ahmadi, S.; Yeh, K.; Kaplowitz, N. Redox
regulation of tumor necrosis factor signaling. Antioxid. Redox Signal., 2009,
11(9), 2245-63.
[71] Circu, M. L.; Aw, T. Y. Reactive oxygen species, cellular redox systems, and
apoptosis. Free Radic. Biol. Med., 2010, 48(6), 749-62.
[72] Masella, R.; Di Benedetto, R.; Vari, R.; Filesi, C.; Giovannini, C. Novel
mechanisms of natural antioxidant compounds in biological systems:
involvement of glutathione and glutathione-related enzymes. J. Nutr.
Biochem., 2005, 16(10), 577-86.
[73] Argyrou, A.; Blanchard, J. S. Flavoprotein disulfide reductases: advances in
chemistry and function. Prog. Nucleic Acid. Res. Mol. Biol., 2004, 78, 89-
142.
[74] Huang, Z. A.; Yang, H.; Chen, C.; Zeng, Z.; Lu, S. C. Inducers of gamma-
glutamylcysteine synthetase and their effects on glutathione synthetase
expression. Biochim. Biophys. Acta, 2000, 1493(1-2), 48-55.
[75] Glantzounis, G. K.; Tsimoyiannis, E. C.; Kappas, A. M.; Galaris, D. A. Uric
acid and oxidative stress. Curr. Pharm. Des., 2005, 11(32), 4145-51.
[76] Frei, B.; Stocker, R.; Ames, B. N. Antioxidant defenses and lipid
peroxidation in human blood plasma. Proc. Natl. Acad. Sci. USA, 1988,
85(24), 9748-52.
[77] Kuzkaya, N.; Weissmann, N.; Harrison, D. G.; Dikalov, S. Interactions of
peroxynitrite with uric acid in the presence of ascorbate and thiols:
implications for uncoupling endothelial nitric oxide synthase. Biochem.
Pharmacol., 2005, 70(3), 343-54.
[78] Fukumoto, L. R.; Mazza, G. Assessing antioxidant and prooxidant activities
of phenolic compounds. J. Agric. Food Chem., 2000, 48(8), 3597-604.
[79] Duthie, G. G.; Pedersen, M. W.; Gardner, P. T.; Morrice, P. C.; Jenkinson,
A. M.; McPhail, D. B.; Steele, G. M. The effect of whisky and wine
consumption on total phenol content and antioxidant capacity of plasma from
healthy volunteers. Eur. J. Clin. Nutr., 1998, 52(10), 733-6.
[80] Cao, G.; Russell, R. M.; Lischner, N.; Prior, R. L. Serum antioxidant
capacity is increased by consumption of strawberries, spinach, red wine or
vitamin C in elderly women. J. Nutr., 1998, 128(12), 2383-90.
[81] Leenen, R.; Roodenburg, A. J.; Tijburg, L. B.; Wiseman, S. A. A single dose
of tea with or without milk increases plasma antioxidant activity in humans.
Eur. J. Clin. Nutr., 2000, 54(1), 87-92.
[82] Fernandez-Pachon, M. S.; Villano, D.; Troncoso, A. M.; Garcia-Parrilla, M.
C. Antioxidant capacity of plasma after red wine intake in human volunteers.
J. Agric. Food Chem., 2005, 53(12), 5024-9.
[83] Lotito, S. B.; Frei, B. The in crease in human plasma antioxidant capacity
after apple consumption is due to the metabolic effect of fructose on urate,
not apple-derived antioxidant flavonoids. Free Radic. Biol. Med., 2004,
37(2), 251-8.
[84] Frank, T.; Netzel, G.; Kammerer, D. R.; Carle, R.; Kler, A.; Kriesl, E.;
Bitsch, I.; Bitsch, R.; Netzel, M. Consumption of Hibiscus sabdariffa L.
aqueous extract and its impact on systemic antioxidant potential in healthy
subjects. J Sci Food Agric. 2012, doi: 10.1002/jsfa.5615.
[85] Sroka, Z.; Cisowski, W. Hydrogen peroxide scavenging, antioxidant and
anti-radical activity of some phenolic acids. Food Chem. Toxicol., 2003,
41(6), 753-8.
[86] Kawabata, J.; Saito, S. DPPH (=2,2-diphenyl-1-picrylhydrazyl) radical-
scavenging reaction of protocatechuic acid (=3,4-dihydroxybenzoic acid):
Difference in reactivity between acids and their esters. Helvetica Chimica
Acta, 2006, 89(7), 1395-1407.
[87] Arakawa, R.; Yamaguchi, M.; Hotta, H.; Osakai, T.; Kimoto, T. Product
analysis of caffeic acid oxidation by on-line electrochemistry/electrospray
ionization mass spectrometry. J. Am. Soc. Mass Spectrom. 2004, 15(8),
1228-36.
[88] Saito, S.; Kawabata, J. A novel oxidative dimer from protocatechuic esters:
contribution to the total radical scavenging ability of protocatechuic esters.
Biosci. Biotechnol. Biochem., 2008, 72(7), 1877-80.
[89] Reis, B.; Martins, M.; Barreto, B.; Milhazes, N.; Garrido, E. M.; Silva, P.;
Garrido, J.; Borges, F. Structure-property-activity relationship of phenolic
acids and derivatives. Protocatechuic acid alkyl esters. J. Agric. Food
Chem.,2010, 58(11), 6986-93.
[90] Siquet, C.; Paiva-Martins, F.; Lima, J. L.; Reis, S.; Borges, F. Antioxidan t
profile of dihydroxy- and trihydroxyphenolic acids--a structure-activity
relationship study. Free Radic. Res., 2006, 40(4), 433-42.
[91] Saito, S.; Okamoto, Y.; Kawabata, J. Effects of alcoholic solvents on
antiradical abilities of protocatechuic acid and its alkyl esters. Biosci.
Biotechnol. Biochem., 2004, 68(6), 1221-7.
[92] Sentandreu, E.; Navarro, J. L.; Sendra, J. M. Reduction kinetics of the
antiradical probe 2,2-diphenyl-1-picrylhydrazyl in methanol and acetonitrile
by the antiradical activity of protocatechuic acid and protocatechuic acid
methyl ester. J. Agric. Food Chem., 2008, 56(13), 4928-36.
[93] Saito, S.; Okamoto, Y.; Kawabata, J.; Kasai, T. Quinone hemiacetal
formation from protocatechuic acid during the DPPH radical scavenging
reaction. Biosci. Biotechnol. Biochem., 2003, 67(7), 1578-9.
[94] Saito, S.; Kurakane, S.; Seki, M.; Takai, E.; Kasai, T.; Kawabata, J. Radical
scavenging activity of dicaffeoyloxycyclohexanes: contribution of an
intramolecular interaction of two caffeoyl residues. Bioorg. Med. Chem.,
2005, 13(13), 4191-9.
[95] Guan, S.; Jiang, B.; Bao, Y. M.; An, L. J. Protocatechuic acid suppresses
MPP+ -induced mitochondrial dysfunction and apoptotic cell death in PC12
cells. Food Chem. Toxicol., 2006, 44(10), 1659-66.
[96] Shi, G. F.; An, L. J.; Jiang, B.; Guan, S.; Bao, Y. M. Alpinia protocatechuic
acid protects against oxidative damage in vitro and reduces oxidative stress
in vivo. Neuro sci. Lett., 2006, 403(3), 206-10.
[97] Tarozzi, A.; Morroni, F.; Hrelia, S.; Angeloni, C.; Marchesi, A.; Cantelli-
Forti, G.; Hrelia, P. Neuroprotective effects of anthocyanins and their in vivo
metabolites in SH-SY5Y cells. Neuro sci. Lett., 2007, 424(1), 36-40.
[98] Hsu, C. C.; Hsu, C. L.; Tsai, S. E.; Fu, T. Y.; Yen, G. C. Protective effect of
Millettia reticulata Benth against CCl(4)-induced hepatic damage and
inflammatory action in rats. J. Med. Food., 2009, 12(4), 821-8.
[99] Chou, T. H.; Ding, H. Y.; Lin, R. J.; Liang, J. Y.; Liang, C. H. Inhibition of
melanogenesis and oxidation by protocatechuic acid from Origanum vulgare
(oregano). J. Nat. Prod., 2010, 73(11), 1767-74.
[100] Giovannini, C.; Scazzocchio, B.; Matarrese, P.; Vari, R.; D'Archivio, M.; Di
Benedetto, R.; Casciani, S.; Dessi, M. R.; Straface, E.; Malorni, W.; Masella,
R. Apoptosis induced by oxidized lipids is associated with up-regulation of
p66Shc in intestinal Caco-2 cells: protective effects of phenolic compounds.
J. Nutr. Bio chem., 2008, 19(2), 118-28.
[101] Nakamura, Y.; Torikai, K.; Ohigashi, H. Toxic dose of a simple phenolic
antioxidant, protocatechuic acid, attenuates the glutathione level in ICR
mouse liver and kidney. J. Agric. Food Chem., 2001, 49(11), 5674-8.
[102] de la Torre, M. R.; Casado, A.; Lopez-Fernandez, M. E.; Carrascosa, D.;
Casado, M. C.; Venarucci, D.; Venarucci, V. Human aging brain disorders:
role of antioxidant enzymes. Neurochem. Res., 1996, 21(8), 885-8.
[103] An, L. J.; Guan, S.; Shi, G. F.; Bao, Y. M.; Duan, Y. L.; Jiang, B.
Protocatechuic acid from Alpinia oxyphylla against MPP+-induced
neurotoxicity in PC12 cells. Food Chem. Toxicol., 2006, 44(3), 436-43.
[104] Zhang, X.; Shi, G. F.; Liu, X. Z.; An, L . J.; Guan, S. Anti-agein g effects of
protocatechuic acid from Alpinia on spleen and liver antioxidative system of
senescent mice. Cell. Biochem. Funct., 2011, 29(4), 342-7.
[105] Masella, R.; Vari, R.; D'Archivio , M.; Di Benedetto, R.; Matarrese, P.;
Malorni, W.; Scazzocchio, B.; Giovannini, C. Extra virgin olive oil
biophenols inhibit cell-mediated oxidation of LDL by increasing the mRNA
transcription of glutathione-related enzymes. J. Nutr., 2004, 134(4), 785-91.
[106] Wasserman, W. W.; Fahl, W. E. Functional antioxidant responsive elements.
Proc. Natl. Acad. Sci. USA, 1997, 94(10), 5361-6.
[107] Nguyen, T.; Nioi, P.; Pickett, C. B. The Nrf2-antioxidant response element
signaling pathway and its activation by oxidative stress. J. Biol. Chem.,
2009, 284(20), 13291-5.
[108] Itoh, K.; Wakabayashi, N.; Katoh, Y.; Ishii, T.; O'Connor, T.; Yamamoto, M.
Keap1 regulates both cytoplasmic-nuclear shuttling and degradation of Nrf2
in response to electrophiles. Genes Cells, 2003, 8(4), 379-91.
Protocatechuic Acid and Human Disease Prevention Current Medicinal Chemistry, 2012 Vol. 19, No. 18 2915
[109] Galanis, A.; Pap pa, A.; Giannakakis, A.; Lanitis, E.; Dangaj, D .;
Sandaltzopoulos, R. Reactive oxygen species and HIF-1 signalling in cancer.
Cancer Le tt., 2008, 266(1), 12-20.
[110] Liu, B.; Chen, Y.; St Clair, D. K., ROS and p53: a versatile partnership. Free
Radic. Biol. Med., 2008, 44(8), 1529-35.
[111] Huang, H. C.; Nguyen, T.; Pickett, C. B., Phosphorylation of Nrf2 at Ser-40
by protein kinase C regulates antioxidant response element-mediated
transcription. J. Biol. Chem., 2002, 277(45), 42769-74.
[112] Nakaso, K.; Yano, H.; Fukuhara, Y.; Takeshima, T.; Wada-Isoe, K.;
Nakashima, K., PI3K is a key molecule in the Nrf2-mediated regulation of
antioxidative proteins by hemin in human neuroblastoma cells. FEBS Lett.,
2003, 546(2-3), 181-4.
[113] D'Arch ivio, M.; Scazzocchio, B.; Filesi, C.; Vari, R.; Maggiorella, M. T.;
Sernicola, L.; Santangelo, C.; Giovan nini, C.; Masella, R. Oxidised LDL up-
regulate CD36 expression by the Nrf2 pathway in 3T3-L1 preadipocytes.
FEBS Lett., 2008, 582(15), 2291-8.
[114] Nguyen, T.; Yang, C. S.; Pickett, C. B. The pathways and molecular
mechanisms regulating Nrf2 activation in response to chemical stress. Free
Radic. Biol. Med., 2004, 37(4), 433-41.
[115] Nerland, D. E. The antioxidant/electrophile response element motif. Drug
Metab. Re v., 2007, 39(1), 235-48.
[116] Harvey, C. J.; Thimmulappa, R. K.; Singh, A.; Blake, D. J.; Ling, G.;
Wakabayashi, N.; Fujii, J.; Myers, A.; Biswal, S., Nrf2-regulated glutathione
recycling independent of biosynthesis is critical for cell survival during
oxidative stress. Free Radic. Biol. Med., 2009, 46(4), 443-53.
[117] Soyalan, B.; Minn, J.; Schmitz, H. J.; Schrenk, D.; Will, F.; Dietrich, H.;
Baum, M.; Eisenbrand, G.; Janzowski, C., Apple juice intervention
modulates expression of ARE-dependent genes in rat colon and liver. Eur. J.
Nutr., 2011, 50(2), 135-43.
[118] Vari, R.; D'Archivio, M.; Filesi, C.; Carotenuto, S.; Scazzocchio, B.;
Santangelo, C.; Giovannini, C.; Masella, R. Protocatechuic acid induces
antioxidant/detoxifying enzyme expression through JNK-mediated Nrf2
activation in murine macrophages. J. Nutr. Biochem., 2011, 22(5), 409-17.
[119] Sica, A.; Rubino, L.; Mancino, A.; Larghi, P.; Porta, C.; Rimoldi, M.;
Solinas, G.; Locati, M.; Allavena, P.; Mantovani, A. Targeting tumour-
associated macrophages. Expert Opin. Ther. Targets, 2007, 11(9), 1219-29.
[120] Yan, Z. Q.; Hansson, G. K. Innate immunity, macrophage activation, and
atherosclerosis. Immunol. Rev., 2007, 219, 187-203.
[121] Scr ivo, R.; Vasile, M.; Bartosiewicz, I.; Valesini, G. Inflammation as
"common soil" of the multifactorial diseases. Autoimmun. Rev., 2011, 10(7),
369-74.
[122] Feghali, C. A.; Wright, T. M. Cytokines in acute and chronic inflammation.
Front. Biosci., 1997, 2, d12-26.
[123] Lawrence, T.; Gilroy, D. W. Chronic inflammation: a failure of resolution?
Int. J. Exp. Pathol., 2007, 88(2), 85-94.
[124] Fonseca, M. I.; Chu, S. H.; Berci, A. M.; Benoit, M. E.; Peters, D. G.;
Kimura, Y.; Tenner, A. J. Contribution of complement activation pathways
to neuropathology differs among mouse models of Alzheimer's disease. J.
Neuroinflammation, 2011, 8(1), 4.
[125] Medzhitov, R. Inflammation 2010: new adventures of an old flame. Cell,
2010, 140(6), 771-6.
[126] Wolowczuk, I.; Verwaerde, C.; Viltart, O.; Delanoye, A.; Delacre, M.; Pot,
B.; Grangette, C. Feeding our immune system: impact on metabolism. Clin.
Dev. Immunol., 2008, 2008, 639803.
[127] Santangelo, C.; Vari, R.; Scazzocchio, B.; Di Benedetto, R.; Filesi, C.;
Masella, R. Polyphenols, intracellular signalling and inflammation. Ann. Ist.
Super. Sanita., 2007, 43(4), 394-405.
[128] Spencer, J. P. Beyond antioxidants: the cellular and molecular interactions of
flavonoids and how these underpin their actions on the brain. Proc. Nutr.
Soc., 2010, 69(2), 244-60.
[129] Sears, B.; Ricordi, C. Anti-inflammatory nutrition as a pharmacological
approach to treat obesity. J. Obes., 2011, pii: 431985.
[130] Min, S. W.; Ryu, S. N.; Kim, D. H. Anti-inflammatory effects of black rice,
cyanidin-3-O-beta-D-glycoside, and its metabolites, cyanidin and
protocatechuic acid. Int. Immunopharmacol., 2010, 10(8), 959-66.
[131] Wang, D.; Wei, X.; Yan, X.; Jin, T.; Ling, W. Protocatechuic acid, a
metabolite of anthocyanins, inhibits monocyte adhesion and reduces
atherosclerosis in apolipoprotein E-deficient mice. J. Agric. Food Chem.,
2010, 58(24), 12722-8.
[132] Manicone, A. M.; McGuire, J. K. Matrix metalloproteinases as modulators of
inflammation. Semin. Cell. Dev. Biol., 2008, 19(1), 34-41.
[133] Lawrence, T.; Fong, C. The resolution of inflammation: anti-inflammatory
roles for NF-kappaB. Int. J. Biochem. Cell. Biol., 2010, 42(4), 519-23.
[134] Moncada, S.; Higgs, E. A. The discovery of nitric oxide and its role in
vascular biology. Br. J. Pharmacol., 2006, 147(Suppl 1), S193-201.
[135] Ignarro, L. J.; Byrns, R. E.; Sumi, D.; de Nigris, F.; Napoli, C. Pomegranate
juice protects nitric oxide against oxidative destruction and enhances the
biological actions of nitric oxid e. Nitric Oxide, 2006, 15(2), 93-102.
[136] Luiking, Y. C.; Engelen, M. P.; Deutz, N. E. Regulation of nitric oxide
production in health and disease. Curr. Opin. Clin. Nutr. Metab. Care, 2010,
13(1), 97-104.
[137] Nathan, C. Nitric oxide as a secretory product of mammalian cells. Faseb J.,
1992, 6(12), 3051-64.
[138] Rajapakse, N. W.; Mattson, D. L. Role of L-arginine in nitric oxide
production in health and hypertension. Clin. Exp. Pharmacol. Physiol., 2009,
36(3), 249-55.
[139] Ugusman, A.; Zakaria, Z.; Hui, C. K.; Nordin, N. A. Piper sarmentosum
increases nitric oxide production in oxidative stress: a study on human
umbilical vein endothelial cells. Clinics (Sao Paulo) 2010, 65(7), 709-14.
[140] Cichocki, M.; Blumczynska, J.; Baer-Dubowska, W. Naturally occurring
phenolic acids inhibit 12-O-tetradecanoylphorbol-13-acetate induced NF-
kappaB, iNOS and COX-2 activation in mouse epidermis. Toxicology, 2010,
268(1-2), 118-24.
[141] Greig, F. H.; Kennedy, S.; Spickett, C. M. Physiological effects of oxidized
phospholipids and their cellular signaling mechanisms in inflammation. Free
Radic. Biol.M ed., 2012, 52(2), 266-80.
[142] Grosser, T. The pharmacology of selective inhibition of COX-2. Thromb.
Haemost., 2006, 96(4), 393-400.
[143] Ashraf, M. Z.; Kar, N. S.; Podrez, E. A. Oxidized phospholipids: biomarker
for cardiovascular diseases. Int. J. Biochem. Cell. Biol., 2009, 41(6), 1241-4.
[144] Verouti, S. N.; Fragopoulou, E.; Karantonis, H. C.; Dimitriou, A. A.;
Tselepis, A. D.; Antonopoulou, S.; Nomikos, T.; Demopoulos, C. A. PAF
effects on MCP-1 and IL-6 secretion in U-937 monocytes in comparison
with OxLDL and IL-1 beta effects. Atherosclerosis, 2011, 219(2), 519-25.
[145] Masella, R.; Cantafora, A.; Modesti, D.; Cardilli, A.; Gennaro, L.; Bocca, A.;
Coni, E. Antioxidant activity of 3,4-DHPEA-EA and protocatechuic acid: a
comparative assessment with other olive oil biophenols. Redox Rep., 1999,
4(3), 113-21.
[146] Di Benedetto, R.; Vari, R.; Scazzocchio, B.; Filesi, C.; Santangelo, C.;
Giovannini, C.; Matarrese, P.; D'Archivio, M.; Masella, R. Tyrosol, the
major extra virgin olive oil compound, restored intracellular antioxidant
defences in spite of its weak antioxidative effectiveness. Nutr. Metab.
Cardiov asc. Dis., 2007, 17(7), 535-45.
[147] Kim , H. P.; Son, K. H.; Chang, H. W.; Kang, S. S. Anti-inflammatory plant
flavonoids and cellular action mechanisms. J. Pharmacol. Sci., 2004, 96(3),
229-45.
[148] Kopf, M.; Bachmann, M. F.; Marsland, B. J. Averting inflammation by
targeting the cytokine environment. Nat. Rev. Drug. Discov., 2010, 9(9),
703-18.
[149] Wong, M. M.; Fish, E. N. Chemokines: attractive mediators of the immune
response. Semin. Immunol., 2003, 15(1), 5-14.
[150] Mohamed-Ali, V.; Armstrong, L.; Clarke, D.; Bolton, C. H.; Pinkney, J. H.
Evidence for the regulation of levels of plasma adhesion molecules by
proinflammatory cytokines and their soluble receptors in type 1 diabetes. J.
Intern. Med., 2001, 250(5), 415-21.
[151] Aso, Y.; Okumura, K.; Yoshida, N.; Tayama, K.; Kanda, T.; Kobayashi, I.;
Takemura, Y.; Inukai, T. Plasma interleukin-6 is associated with coagulation
in poorly controlled patients with Type 2 diabetes. Diabet. Med., 2003,
20(11), 930-4.
[152] Kitamoto, S.; Egashira, K. Anti-monocyte chemoattractant protein-1 gene
therapy for cardiovascular diseases. Expert. Rev. Cardiovasc. Ther., 2003,
1(3), 393-400.
[153] Hatanaka, E.; Monteagudo, P. T.; Marrocos, M. S.; Campa, A. Neutrophils
and monocytes as potentially important sources of proinflammatory
cytokines in diabetes. Clin. Exp. Immunol., 2006, 146(3), 443-7.
[154] Tunon, M. J.; Garcia-Mediavilla, M. V.; Sanchez-Campos, S.; Gonzalez-
Gallego, J. Potential of flavonoids as anti-inflammatory agents: modulation
of pro-inflammatory gene expression and signal transduction pathways. Curr.
Drug. Metab., 2009, 10(3), 256-71.
[155] Ricklin, D.; Hajishengallis, G.; Yang, K.; Lambris, J. D. Complement: a key
system for immune surveillance and homeostasis. Nat. Immunol.,2010,
11(9), 785-97.
[156] Ag er, R. R.; Fonseca, M. I.; Chu, S. H.; Sanderson, S. D.; Taylor, S. M.;
Woodruff, T. M.; Tenner, A. J. Microglial C5aR (CD88) expression
correlates with amyloid-beta deposition in murine models of Alzh eimer's
disease. J. Neurochem., 2010, 113(2), 389-401.
[157] Moon, H. I.; Lee, J. H.; Lee, Y. C.; Kim, S. K. Inhibitory Effects of Isolated
Compounds from Black Coloured Rice Bran on the Complement Classical
Pathway. Phytother. Res., 2011, doi: 10.1002/ptr.3485.
[158] Plotn ikov, A.; Zehorai, E.; Procaccia, S.; Seger, R. The MAPK cascades:
Signaling components, nuclear roles and mechanisms of nuclear
translocation. Biochim. Biophys. Acta., 2011, 1813(9):1619-33.
[159] Bonizzi, G.; Karin, M. The two NF-kappaB activation pathways and their
role in innate and adaptive immunity. Trends Immunol., 2004, 25(6), 280-8.
[160] Moynagh, P. N. The NF-kappaB pathway. J. Cell. Sci., 2005, 118(20), 4589-
92.
[161] Tak, P. P.; Firestein, G. S. NF-kappaB: a key role in inflammatory diseases.
J. Clin. In vest., 2001, 107(1), 7-11.
[162] Kar in, M.; Yamamoto, Y.; Wang, Q. M. The IKK NF-kappa B system: a
treasure trove for drug development. Nat. Rev. Drug. Discov., 2004, 3(1),
17-26.
[163] Hayden, M. S.; Ghosh, S. Signaling to NF-kappaB. Genes. Dev., 2004,
18(18), 2195-224.
[164] Nam, N. H. Naturally occurring NF-kappaB inhibitors. Mini Rev. Med.
Chem., 2006, 6(8), 945-51.
[165] Ivanenkov, Y. A.; Balakin, K. V.; Lavrovsky, Y. Small molecule inhibitors
of NF-kB and JAK/STAT signal transduction pathways as promising anti-
inflammatory therapeutics. Mini Rev. Med. Chem., 2011, 11(1), 55-78.
[166] Lin, H. H.; Chen, J. H.; Chou, F. P.; Wang, C. J. Protocatechuic acid inhibits
cancer cell metastasis involving the down-regulation of Ras/Akt/NF-kappaB
2916 Current Medicinal Chemistry, 2012 Vol. 19, No. 18 Masella et al.
pathway and MMP-2 production by targeting RhoB activation. Br. J.
Pharmacol., 2011, 162(1), 237-54.
[167] Kaminska, B. MAPK signalling pathways as molecular targets for anti-
inflammatory therapy--from molecular mechanisms to therapeutic benefits.
Biochim. Biophys. Acta., 2005, 1754(1-2), 253-62.
[168] Mayor, F., Jr.; Jurado-Pueyo, M.; Campos, P. M.; Murga, C. Interfering with
MAP kinase docking interactions: implications and perspective for the p38
route. Cell. Cycle., 2007, 6(5), 528-33.
[169] Lin, C. Y.; Huang, C. S.; Huang, C. Y.; Yin, M. C. Anticoagulatory,
antiinflammatory, and antioxidative effects of protocatechuic acid in diabetic
mice. J. Agric. Food Chem., 2009, 57(15), 6661-7.
[170] Yan, J. J.; Jung, J. S.; Hong, Y. J.; Moon, Y. S.; Suh, H. W.; Kim, Y. H.;
Yun-Choi, H. S.; Song, D. K. Protective effect of protocatechuic acid
isopropyl ester against murine models of sepsis: inhibition of TNF-alpha and
nitric oxide production and augmentation of IL-10. Biol. Pharm. Bull., 2004,
27(12), 2024-7.
[171] Liu, W. H.; Lin, C. C.; Wang, Z. H.; Mong, M. C.; Yin, M. C. Effects of
protocatechuic acid on trans fat induced hepatic steatosis in mice. J. Agric.
Food Chem., 2010, 58(18), 10247-52.
[172] Nakamura, Y.; Torikai, K.; Ohigashi, H. A catechol antioxidant
protocatechuic acid potentiates inflammatory leukocyte-derived oxidative
stress in mo use skin via a tyrosinase bioactivation pathway. Free Radic. Biol.
Med., 2001, 30(9), 967-78.
[173] Glass, C. K.; Witztum, J. L. Atherosclerosis. the road ahead. Cell, 2001,
104(4), 503-16.
[174] Vari, R.; D'Archivio, M.; Filesi, C.; Carotenuto, S.; Scazzocchio , B.;
Santangelo, C.; Giovannini, C.; Masella, R. Protocatechuic acid induces
antioxidant/detoxifying enzyme expression through JNK-mediated Nrf2
activation in murine macrophages. J. Nutr. Biochem., 2011, 22(5), 409-17.
[175] Dansky, H. M.; Barlow, C. B.; Lominska, C.; Sikes, J. L.; Kao, C.; Weinsaft,
J.; Cybulsky, M. I.; Smith, J. D. Adhesion of monocytes to arterial
endothelium and initiation of atherosclerosis are critically dependent on
vascular cell adhesion molecule-1 gene dosage. Arterioscler. Thromb. Vasc.
Biol., 2001, 21(10), 1662-7.
[176] Zernecke, A.; Weber, C. Chemokines in the vascular inflammatory response
of athero sclerosis. Card iovasc. Res. , 2010, 86(2), 192-201.
[177] Tabas, I.; Seimon, T.; Timmins, J.; Li, G.; Lim, W. Macrophage apoptosis in
advanced atherosclerosis. Ann. N. Y. Acad. Sci., 2009, 1173(Suppl 1), E40-
5.
[178] Santang elo, C.; Vari, R.; Scazzocchio, B.; Filesi, C.; D'Archivio, M.;
Giovannini, C.; Masella, R. CCAAT/enhancer-binding protein-beta
participates in oxidized LDL-enhanced proliferation in 3T3-L1 cells.
Biochimie., 2011, 93(9), 1510-9.
[179] Rechn er, A. R.; Kroner, C. Anthocyanins and colonic metabolites of dietary
polyphenols inhibit platelet function. Thromb. Res., 2005, 116(4), 327-34.
[180] Holv oet, P.; Lee, D . H.; Steffes, M.; Gro ss, M.; Jaco bs, D. R., Jr. Association
between circulating oxidized low-density lipoprotein and incidence of the
metabolic syndrome. Jama, 2008, 299(19), 2287-93.
[181] Masella, R.; Vari, R.; D'Archivio, M.; Santangelo, C.; Scazzocchio, B.;
Maggiorella, M. T.; Sernicola, L.; Titti, F.; Sanchez, M.; Di Mario, U.; Leto,
G.; Giovannini, C. Oxidised LDL modulate adipogenesis in 3T3-L1
preadipocytes by affecting the balance between cell proliferation and
differentiation. FEBS Lett., 2006, 580(10), 2421-9.
[182] Cusi, K.; Maezono, K.; Osman, A.; Pendergrass, M.; Patti, M. E.;
Pratipanawatr, T.; DeFronzo, R. A.; Kahn, C. R.; Mandarino, L. J. Insulin
resistance differentially affects the PI 3-kinase- and MAP kinase-mediated
signaling in human muscle. J. Clin. Invest., 2000, 105(3), 311-20.
[183] Folli, F.; Saad, M. J.; Backer, J. M.; Kahn, C. R. Regulation of
phosphatidylinositol 3-kinase activity in liver and muscle of animal models
of insulin-resistant and insulin-deficient diabetes mellitus. J. Clin. Invest.,
1993, 92(4), 1787-94.
[184] Adisakwattana, S.; Charoenlertkul, P.; Yibchok-Anun, S. alpha-Glucosidase
inhibitory activity of cyanidin-3-galactoside and synergistic effect with
acarbose. J. Enzyme. Inhib. Med. Chem., 2009, 24(1), 65-9.
[185] Takikawa, M.; Inoue, S.; Horio, F.; Tsuda, T. Dietary anthocyanin-rich
bilberry extract ameliorates hyperglycemia and insulin sensitivity via
activation of AMP-activated protein kinase in diabetic mice. J. Nutr., 2010,
140(3), 527-33.
[186] Nizamutdinova, I. T.; Jin, Y. C.; Chung, J. I.; Shin, S. C.; Lee, S. J.; Seo, H.
G.; Lee, J. H.; Chang, K. C.; Kim, H. J. The anti-diabetic effect of
anthocyanins in streptozotocin-induced diabetic rats through glucose
transporter 4 regulation and prevention of insulin resistance and pancreatic
apoptosis. Mol. Nutr. Food Res., 2009, 53(11), 1419-29.
[187] Seymour, E. M.; Lewis, S. K.; Urcuyo-Llanes, D. E.; Tanone, II; Kirakosyan,
A.; Kaufman, P. B.; Bolling, S. F. Regular tart cherry intake alters abdominal
adiposity, adipose gene transcription, and inflammation in obesity-prone rats
fed a high fat diet. J. Med. Food., 2009, 12(5), 935-42.
[188] Harini, R.; Pugalendi, K. V. Antihyperglycemic effect of protocatechuic acid
on streptozotocin-diabetic rats. J. Basic Clin. Physiol. Pharm acol., 2010,
21(1), 79-91.
[189] Harini, R.; Pugalendi, K. V. Antioxidant and antihyperlipidaemic activity of
protocatechuic acid on streptozotocin-diabetic rats. Redox. Rep., 2010,15(2),
71-80.
[190] Takeuchi, M.; Yamagishi, S. Alternative routes for the formation of
glyceraldehyde-derived AGEs (TAGE) in vivo. Med. Hypotheses., 2004,
63(3), 453-5.
[191] Desvergne, B.; Wahli, W. Peroxisome proliferator-activated receptors:
nuclear control of metabolism. Endocr. Rev., 1999, 20(5), 649-88.
[192] Spiegelman, B. M. PPAR-gamma: adipogenic regulator and
thiazolidinedione receptor. Diabetes, 1998, 47(4), 507-14.
[193] Scazzocchio , B.; Vari, R.; Filesi, C.; D'Archivio, M.; Santangelo, C.;
Giovannini, C.; Iacovelli, A.; Silecchia, G.; Li Volti, G.; Galvano, F.;
Masella, R. Cyanidin-3-O-beta-glucoside and protocatechuic acid exert
insulin-like effects by upregulating PPARgamma activity in human omental
adipocytes. Diabetes, 2011, 60(9), 2234-44.
[194] D'Archivio , M.; Santangelo, C.; Scazzocchio, B.; Vari, R.; Filesi, C.;
Masella, R.; Giovannini, C. Modulatory effects of polyphenols on apoptosis
induction: relevance for cancer prevention. Int. J. Mol. Sci., 2008, 9(3), 213-
28.
[195] Giovannini, C.; Scazzocchio, B.; Vari, R.; Santangelo, C.; D'Archivio, M.;
Masella, R. Apoptosis in cancer and atherosclerosis: polyphenol activities.
Ann. Ist. Super. Sanita., 2007, 43(4), 406-16.
[196] Birt, D. F.; Hendrich, S.; Wang, W. Dietary agents in cancer prevention:
flavonoids and isoflavonoids. Pharmacol. Ther., 2001, 90(2-3), 157-77.
[197] Kris-Etherton, P. M.; Keen, C. L. Evidence that the antioxidant flavonoids in
tea and cocoa are beneficial for cardiovascular health. Curr. Opin. Lipido l.,
2002, 13(1), 41-9.
[198] Orsini, F.; Moroni, M.; Contursi, C.; Yano, M.; Pelicci, P.; Giorgio, M.;
Migliaccio, E. Regulatory effects of the mitochondrial energetic status on
mitochondrial p66Shc. Biol. Chem., 2006, 387(10-11), 1405-10.
[199] Wu, G. S. The functional interactions between the p53 and MAPK signaling
pathway s. Cancer Biol . Ther., 2004, 3(2), 156-61.
[200] Yoshida, K. PKCdelta signaling: mechanisms of DNA damage response and
apoptosis. Cell Signal 2007, 19(5), 892-901.
[201] Zhou-Stache, J.; Buettner, R.; Artmann, G.; Mittermayer, C.; Bosserhoff, A.
K. Inhibition of TNF-alpha induced cell death in human umbilical v ein
endothelial cells and Jurkat cells by protocatechuic acid. Med. Biol. Eng.
Comput., 2002, 40(6), 698-703.
[202] An, L. J.; Guan, S.; Jiang, B.; Bao, Y. M. Protocatechuic acid suppresses
MPP+-induced mitochondrial dysfunction and apoptotic cell death in PC12
cells. Food and Chemical Toxicology, 2006, 44(10), 1659-1666.
[203] Guan, S.; Ge, D.; Liu, T. Q.; Ma, X. H.; Cui, Z. F. Protocatech uic acid
promotes cell proliferation and reduces basal apoptosis in cultured neural
stem cells. Toxicol. In vitro, 2009, 23(2), 201-8.
[204] Guan, S.; Bao, YM.; Bo, Jiang.; An, L.J. Protective effect of protocatechuic
acid from Alpinia oxyphylla on hydrogen peroxide-induced oxidative PC12
cell death. Eur. J. Pharmacol., 2006, 538, 73-9.
[205] Tarozzi, A.; Merlicco, A.; Morron i, F.; Franco, F.; Cantelli-Forti, G.; Teti,
G.; Falconi, M.; Hrelia, P. Cyanidin 3-O-glucopyranoside protects and
rescues SH-SY5Y cells against amyloid-beta peptide-induced toxicity.
Neuroreport, 2008, 19(15), 1483-6.
[206] Zhan g, H. N.; An, C. N.; Xu, M.; Guo, D. A.; Li, M.; Pu, X. P.
Protocatechuic acid inhibits rat pheochromocytoma cell damage induced by a
dopaminergic neurotoxin. Biol. Pharm. Bull., 2009, 32(11), 1866-9.
[207] Zhang, H. N.; An, C. N.; Zhang, H. N.; Pu, X. P. Protocatechuic acid inhibits
neurotoxicity induced by MPTP in vivo. Neurosci. Lett.,2010, 474(2), 99-
103.
[208] Ban, J. Y.; Cho, S. O.; Jeon, S. Y.; Bae, K.; Song, K. S.; Seong, Y. H. 3,4-
dihydroxybenzoic acid from Smilacis chinae rhizome protects amyloid beta
protein (25-35)-induced neurotoxicity in cultured rat cortical neurons.
Neurosci. Lett., 2007, 420(2), 184-8.
[209] Song, H. J.; Stevens, C. F.; Gage, F. H. Neural stem cells from adult
hippocampus develop essential properties of functional CNS neurons. Nat.
Neurosci., 2002, 5(5), 438-45.
[210] Zhang, Y. J.; Wu, L.; Zhang, Q. L.; Li, J.; Yin, F. X.; Yuan, Y.
Pharmacokinetics of phenolic compounds of Danshen extract in rat blood
and brain by microdialysis sampling. J. Ethnopharmacol., 2011, 136(1), 129-
36.
[211] Wang, H.; Liu, T. Q.; Zhu, Y. X.; Guan, S.; Ma, X. H.; Cui, Z. F. Effect of
protocatechuic acid from Alpinia oxyphylla on proliferation of human
adipose tissue-derived stromal cells in vitro. Mol. Cell. Biochem., 2009,
330(1-2), 47-53.
[212] Ramos, S. Effects of dietary flavonoids on apoptotic pathways related to
cancer chemoprevention. J. Nutr. Biochem., 2007, 18(7), 427-42.
[213] Anter, J.; Romero-Jimenez, M.; Fernandez-Bedmar, Z.; Villatoro-Pulido, M.;
Analla, M.; Alonso-Moraga, A.; Munoz-Serrano, A. Antigenotoxicity,
cytotoxicity, and apoptosis induction by apigenin, bisabolol, and
protocatechuic acid. J. Med. Food., 2011, 14(3), 276-83.
[214] Ramos, S. Cancer chemoprevention and chemotherapy: dietary polyphenols
and signalling pathway s. Mol. Nutr. Food Res., 2008, 52(5), 507-26.
[215] Tseng, T. H.; Kao, T. W.; Chu, C. Y.; Chou, F. P.; Lin, W. L.; Wang, C. J.
Induction of apoptosis by hibiscus protocatechuic acid in human leukemia
cells via reduction of retinoblastoma (RB) phosphorylation and Bcl-2
expression. Biochem. Pharmacol., 2000, 60(3), 307-15.
[216] Lee, J. C.; Lee, K. Y.; Kim, J.; Na, C. S.; Jung, N. C.; Chung, G. H.; Jang, Y.
S. Extract from Rhus verniciflua Stokes is capable of inhibiting the growth of
human lymphoma cells. Food Chem. Toxicol., 2004, 42(9), 1383-8.
Protocatechuic Acid and Human Disease Prevention Current Medicinal Chemistry, 2012 Vol. 19, No. 18 2917
[217] Jang, H. S.; Kook, S. H.; Son, Y. O.; Kim, J. G.; Jeon, Y. M.; Jang, Y. S.;
Choi, K. C.; Kim, J.; Han, S. K.; Lee, K. Y.; Park, B. K.; Cho, N. P.; Lee, J.
C. Flavonoids purified from Rhus verniciflua Stokes actively inhibit cell
growth and induce apoptosis in human osteosarcoma cells. Biochim.
Biophys. Acta., 2005, 1726(3), 309-16.
[218] Stagos, D.; Kazantzoglou, G.; Magiatis, P.; Mitaku, S.; Anagnostopoulos, K.;
Kouretas, D. Effects of plant phenolics and gr ape extracts from Greek
varieties of Vitis vinifera on Mitomycin C and topoisomerase I-induced
nicking of DNA. Int. J. Mol. Med., 2005, 15(6), 1013-22.
[219] Lin, H. H.; Chen, J. H.; Huang, C. C.; Wang, C. J. Apoptotic effect of 3,4-
dihydroxybenzoic acid on human gastric carcinoma cells involving JNK/p38
MAPK signaling activation. Int. J. Cancer., 2007, 120(11), 2306-16.
[220] Yip, E. C.; Chan, A. S.; Pang, H.; Tam, Y. K.; Wong, Y. H. Protocatechuic
acid induces cell death in HepG2 hepatocellular carcinoma cells through a c-
Jun N-terminal kinase-dependent mechanism. Cell. Biol. Toxicol., 2006,
22(4), 293-302.
[221] Szaefer, H.; Kaczmarek, J.; Rybczynska, M.; Baer-Dubowska, W. The effect
of plant phenols on the expression and activity of phorbol ester-induced PKC
in mouse epidermis. Toxicology, 2007, 230(1), 1-10.
[222] Yin, M. C.; Lin, C. C.; Wu, H. C.; Tsao, S. M.; Hsu, C. K. Apoptotic effects
of protocatechuic acid in human breast, lung, liver, cervix, and prostate
cancer cells: potential mechanisms of action. J. Agric. Food Chem., 2009,
57(14), 6468-73.
[223] Tseng, T. H.; Wang, C. J.; Kao, E. S.; Chu, H. Y. Hibiscus protocatechuic
acid protects against oxidative damage induced by tert-butylhydroperoxide in
rat primary hepatocytes. Chem. Biol. Interact., 1996, 101(2), 137-48.
[224] Ho, H. H.; Chang, C. S.; Ho, W. C.; Liao, S. Y.; Wu, C. H.; Wang, C. J.
Anti-metastasis effects of gallic acid on gastric cancer cells involves
inhibition of NF-kappaB activity and downregulation of PI3K/AKT/small
GTPase signals. Food Chem. Toxicol., 2010, 48(8-9), 2508-16.
[225] Taguri, T.; Tanaka, T.; Kouno, I. Antimicrobial activity of 10 different plant
polyphenols against bacteria causing food-borne disease. Biol. Pharm. Bull.,
2004, 27(12), 1965-9.
[226] Chao, C. Y.; Yin, M. C. Antibacterial e ffects of roselle calyx extracts and
protocatechuic acid in ground beef and apple juice. Foodborne Pathog. Dis.,
2009, 6(2), 201-6.
[227] Yin, M. C.; Chao, C. Y. Anti-Campylobacter, anti-aerobic, and anti-
oxidative effects of roselle calyx extract and protocatechuic acid in ground
beef. Int. J. Food Microbiol., 2008, 127(1-2), 73-7.
[228] D'Arrigo, M.; Ginestra, G.; Mandalari, G.; Furneri, P. M.; Bisignano, G.
Synergism and postantibio tic effect of tobramycin and Melaleuca alternifolia
(tea tree) oil against Staphylococcus aureus and Escherichia coli.
Phytomedicine, 2010, 17(5), 317-22.
[229] Lee, Y. S.; Kang, O. H.; Choi, J. G.; Oh, Y. C.; Chae, H. S.; Kim, J. H.; Park,
H.; Sohn, D. H.; Wang, Z. T.; Kwon, D. Y. Synergistic effects of the
combination of galangin with gentamicin against meth icillin-resistant
Staphylococcus aureus. J. Microbiol., 2008, 46(3), 283-8.
[230] Jayaraman, P.; Sakharkar, M. K.; Lim, C. S.; Tang, T. H.; Sakharkar, K. R.
Activity and interactions of antibiotic and phytochemical combinations
against Pseudomonas aeruginosa in vitro. Int. J. Biol. Sci., 2010, 6(6), 556-
68.
[231] Jayaraman, P.; Sakharkar, K. R.; Sing, L. C.; Chow, V. T.; Sakharkar, M. K.
Insights into antifolate activity of phytochemicals against Pseudomonas
aeruginosa. J. Drug. Target., 2011, 19(3), 179-88.
[232] Ku ete, V.; Nana, F.; Ngameni, B.; Mbaveng, A. T.; Keumedjio, F.; Ngadjui,
B. T. Antimicrobial activity of the crude extract, fractions and compounds
from stem bark of Ficus ovata (Moraceae). J. Ethnopharmacol., 2009, 124(3),
556-61.
[233] Sakharkar, M. K.; Jayaraman, P.; Soe, W. M.; Chow, V. T.; Sing, L. C.;
Sakharkar, K. R. In vitro combinations of antibiotics and phytochemicals
against Pseudomonas aeruginosa. J. Microbiol. Immunol. Infect., 2009,
42(5), 364-70.
[234] Liu, W. H.; Hsu, C. C.; Yin, M. C. In vitro anti-Helicobacter pylori activity
of diallyl sulphides and protocatechuic acid. Phytother. Res., 2008, 22(1), 53-
7.
[235] Rossetto, M.; Lante, A.; Vanzani, P.; Spettoli, P.; Scarpa, M.; Rigo, A. Red
chicories as potent scavengers of highly reactive radicals: a study on their
phenolic composition and peroxyl radical trapping capacity and efficiency. J.
Agric. Food Chem., 2005, 53(21), 8169-75.
[236] Boskou, G.; Salta, F.N.; Chrysostomou, S.; Mylona, A.; Chiou, A.;
Andrikopoulos, N.K. Antioxidant capacity and phenolic profile of table
olives from the Greek market. Food Chem., 2006, 94(4), 558-564.
[237] Al-Farsi, M.; Alasalvar, C.; Morris, A.; Baron, M.; Shahidi, F. Comparison
of antioxidant activity, anthocyanins, carotenoids, and phenolics of three
native fresh and sun-dried date (Phoenix dactylifera L.) varieties grown in
Oman. J. Agric. Food Chem., 2005, 53(19), 7592-9.
[238] Gokmen, V.; Artik, N.; Acar, J.; Kahraman, N.; Poyrazoglu, E. Effects of
various clarification treatments on patulin, phenolic compound and organic
acid compositions of apple juice. Eur. Food. Res. Technol., 2001, 213(3),
194-199.
[239] Natera, R.; Castro, R.; de Valme Garcia-Moreno, M.; Hernandez, M. J.;
Garcia-Barroso, C. Chemometric studies of vinegars from different raw
materials and processes of production. J. Agric. Food Chem., 2003, 51(11),
3345-51.
[240] Ping, L.; Xu-Qing, W.; Huai-Zhou, W.; Yong-Ning, W. High Performance
Liquid Chromatographic Determination of Phenolic Acids in Fruits and
Vegetables. Biomed. Environm. Sci., 1993, 6, 389-398.
[241] Zadernowski, R.; Naczk, M.; Nesterowicz, J. Phenolic acid profiles in some
small berries. J. Agric. Food Chem., 2005, 53(6), 2118-2124.
[242] Minussi, R.C.; Rossi, M.; Bologna, L.; Cordi, L.; Rotilio, D.; Pastore, G.M.;
Duran, N. Phenolic compounds and total antioxidant potential of commercial
wines. Food Chem., 2003, 82, 409-416.
[243] Karadeniz, F.; Durst, R. W.; Wrolstad, R. E. Polyphenolic composition of
raisins. J. Agric. Food Chem., 2000, 48(11), 5343-50.
[244] Garcia, A. A.; Grande, B. C.; Gandara, J. S. Development of a rapid method
based on solid-phase extraction and liquid chromatography with ultraviolet
absorbance detection for the determination of polyphenols in alcohol-free
beers. J. Chr omatogr. A, 2004, 1054(1-2), 175-80.
[245] Milbury, P.E.; Chen, C.Y.; Dolnikowski, G.G.; Blumberg, J.B.
Determination of flavonoids and phenolics and their distribution in almonds.
J. Agric.Food Chem., 2006, 54, 50 27-5033.
[246] Liberatore, L.; Procida, G.; d'Alessandro, N.; Cichelli, A. Solid-phase
extraction and gas chromatographic analysis of phenolic compounds in
virgin olive oil. Food Chemistry, 2001, 73(1), 119-124.
[247] Poyrazoglu, E.; Gokmen, V.; Artik, N. Organic acids and phenolic
compounds in pomegranates (Punica granatum L.) grown in Turkey. Journal
of Food Composition and Analysis, 2002, 15(5), 567-575.
[248] Duenas, M.; Hernandez, T.; Estrella, I. Changes in the con tent of bioactive
polyphenolic compounds of lentils by the action of exogenous enzymes.
Effect on their antioxidant activity. Food Chemistry, 2007, 101(1), 90-97.
Received: November 28, 20 11 R evised: Mar ch 26, 2012 Accepted: March 26, 20 12
... Diets high in vegetables and fruits have been demonstrated to elicit health benefits due to their nutrient and antioxidant-rich composition (Masella et al., 2012). Bioactive compounds such as dietary antioxidants play a key role in the human body protecting itself against oxidative damage, which is known to be associated with aging and degenerative diseases such as cancers and cardiovascular disease (Andre et al., 2010;Masella et al., 2012). ...
... Diets high in vegetables and fruits have been demonstrated to elicit health benefits due to their nutrient and antioxidant-rich composition (Masella et al., 2012). Bioactive compounds such as dietary antioxidants play a key role in the human body protecting itself against oxidative damage, which is known to be associated with aging and degenerative diseases such as cancers and cardiovascular disease (Andre et al., 2010;Masella et al., 2012). Several studies have shown that GP exhibits beneficial antioxidant activity, has antimicrobial actions against bacteria, fungi, and viruses, as well as inhibits low-density lipoprotein oxidation (Bhise et al., 2014;Deng et al., 2011;Jayaprakasha et al., 2003). ...
Article
Full-text available
Grape pomace (GP) is a waste product of the winemaking process and has been proposed as a nutritionally beneficial ingredient, as it contains phenolic compounds, dietary fiber, and antioxidant activity. It can be a polarizing ingredient due to its flavor components. Familiarity has been found to influence consumers’ preferences and sensory perception of food. A sensory test was conducted to evaluate the acceptance, sensory perception, and emotional response to pasta sauces containing GP (3% [3GP], 6% [6GP], 9% [9GP] by volume and control without GP addition). The sensory trials included wine consumers (n = 44) and nonconsumers of wine (n = 58) to determine how consumers’ familiarity with the flavor properties of GP influenced their perception of the pasta sauce. Overall, the addition of GP decreased the liking scores of the GP‐containing sauces, but the wine consumers’ hedonic scores for the control, 3GP, and 9GP were significantly higher than the nonconsumers. Both consumer groups identified that the samples with a higher amount of GP addition were associated with sour, bitter, astringency, grainy, and gritty attributes. However, the wine consumers used more positive emotions to describe their emotional response to the GP‐containing samples. The study identified that GP led to off‐flavors and textures in the pasta sauces. Practical Application GP is currently a waste product, but it has many nutritional benefits. Consumers are increasingly looking for nutritional benefits from their food. When incorporated into pasta sauces, GP decreased the acceptance of the pasta sauce and negatively impacted the flavor and texture. Familiarity has been found to impact consumer acceptance, and wine consumers had a more positive emotional response and higher hedonic scores in response to the GP‐containing pasta sauce than nonconsumers of wine.
... PCA, a phenolic acid chemically known as 3,4-dihydroxybenzoic acid, is naturally present in edible medicinal plants as a secondary metabolite. Its pharmacological activity is primarily attributed to its antioxidant and anti-inflammatory properties [17][18][19]. ...
... However, further investigation is necessary to ascertain the bioavailability of PCA and its specific role in the antioxidant potential in combination with other bioactive components in EAE. Nonetheless, this study indicates that PCA is considered safe at a dose of 100 mg/kg BW/day [54], exhibiting potent antioxidant, antibacterial, anticancer, antihyperlipidemic, antidiabetic, and anti-inflammatory properties [18,19,56,58]. Further research is imperative to evaluate its clinical reliability, safety, and efficacy. ...
Article
Full-text available
The increasing prevalence of age-related neurodegenerative disorders owing to the aging population worldwide poses substantial challenges. This study investigated the neuroprotective effects of protocatechuic acid (PCA), a compound found in various fruits, vegetables, and grains, using a scopolamine-induced hypomnesia mouse model. Six-week-old male C57BL/6J mice were orally administered PCA at doses of 10 and 100 mg/kg body weight per day for two weeks, along with intraperitoneal injections of scopolamine. Learning and memory abilities were assessed using the passive avoidance, Morris water maze, and Y-maze behavioral assays. Biochemical analyses evaluated the levels of oxidative stress markers, including 8-hydroxydeoxyguanosine (8-OHdG) in the blood and malondialdehyde (MDA) in the brain, as well as phase II antioxidant proteins in the hippocampus. Histological examination was conducted to determine hippocampal integrity. Our results demonstrated that PCA administration at 10 mg/kg body weight per day or higher for two weeks (i) significantly ameliorated scopolamine-induced learning and memory impairments, as evidenced by improved performance in behavioral tasks, (ii) reduced plasma 8-OHdG levels and cerebral MDA levels in a dose-dependent manner, (iii) increased antioxidant protein expressions in the hippocampal tissue, and (iv) mitigated histological damage in the hippocampal region of the brain. These findings suggest that oral administration of PCA provides neuroprotective effects against oxidative stress-induced learning and memory impairments, possibly through upregulating antioxidant machinery. Therefore, PCA may serve as a promising dietary supplement for mitigating cognitive deficits associated with neurodegenerative diseases.
... The fundamental relationship between diet, health, and disease has diverted researchers' attention toward phenolic compounds, which are secondary plant metabolites found in fruits and vegetables. Phenolic compounds, such as Protocatechuic Acid (PCA), have shown potential in regulating insulin-signaling pathways, such as IRS-1 and PI3K-Akt [23], and in increasing GLUT-4 translocation and glucose uptake [24], thus preventing and treating T2D [25]. In addition, PCA can enhance antioxidant capacity [26] and preserve skeletal muscle strength and endurance [27]. ...
Article
Full-text available
Background: Exercise training positively modulates myokine secretion and improves glucose metabolism. Herein, we analyzed the effect of moderate-intensity training, detraining, and Protocatechuic Acid (PCA) supplementation on myokine secretions and regulation of insulin-signaling pathways. Methods: A five-arm study was conducted on 47 healthy male Wistar rats, trained at a moderate intensity level for four weeks (T0-T4). Animals were randomly classified into groups according to PCA supplementation and exercise durations: four weeks of Aerobic Training with or without PCA (AT4, AT4-PCA), eight weeks of Aerobic Training with or without PCA (AT8, AT8-PCA), and PCA Vehicle Control (VC). The animals were followed up until week 12 (T12). We decapitated six rats at T0 and T4, four rats per group at T8, and three rats per group at T12. Myokines (IGF-1, IL-6, FGF-21, myostatin, and irisin) were analyzed with ELISA. Western blot analysis measured protein expression of insulin-signaling pathways and GLUT-4 in the gastrocnemius muscle. Results: The IL-6 levels increased significantly (p < 0.01) with 8-week training in AT8 by 34% and AT8-PCA by 32%, compared to groups trained for only 4 weeks (AT4 and AT4-PCA). Similarly, the PI3K, and GLUT-4 expression improved in AT8 and AT8-PCA at T8. Training for 4 weeks improved IGF-1 levels, but a further 14% improvement was observed with 8-week training in AT8 at T8. Myostatin level significantly dropped by 27% even with 4-week training (p < 0.001). However, detraining increased the myostatin levels in all groups, but in AT8-PCA with PCA dose, myostatin reduced by 11% compared to AT8 at T12. PCA supplementation reduced the FGF-21 levels by 54% during detraining at T12 in AT8-PCA compared to AT8. However, the irisin level did not change markedly in any group. Conclusions: Physical training (with and without PCA) modulates myokine production and improves glucose metabolism, but the benefits are lost after detraining.
... Protocatechuic acid (PCA, 3,4-dihydroxybenzoic acid) is the major metabolite of polyphenols abundant in fruits and vegetables [76]. Pretreatment with PCA mitigated oxidative stress by reducing ROS generation through activating the LKB1/AMPK/Nrf-2 pathway and reversed AMPK-dependent PGC1-α to enhance mitochondrial biosynthesis against lipotoxicity-induced oxidative stress in endothelial cells [68]. ...
Article
Full-text available
Excessive intake of free fatty acids (FFAs), especially saturated fatty acids, can lead to atherosclerosis and increase the incidence of cardiovascular diseases. FFAs also contribute to obesity, hyperlipidemia, and nonalcoholic fatty liver disease. Palmitic acid (PA) is human plasma’s most abundant saturated fatty acid. It is often used to study the toxicity caused by free fatty acids in different organs, including vascular lipotoxicity. Fatty acid overload induces endothelial dysfunction through various molecular mechanisms. Endothelial dysfunction alters vascular homeostasis by reducing vasodilation and increasing proinflammatory and prothrombotic states. It is also linked to atherosclerosis, which leads to coronary artery disease, peripheral artery disease, and stroke. In this review, we summarize the latest studies, revealing the molecular mechanism of free fatty acid-induced vascular dysfunction, targeting insulin resistance, reactive oxygen species, inflammation, programmed cell death, ER stress, and mitochondrial dysfunction. Meanwhile, this review provides new strategies and perspectives for preventing and reducing the impact of cardiovascular diseases on human health through the relevant targeting molecular mechanism.
Article
Metabolic dysfunction‐associated steatotic liver disease (MASLD) is highly prevalent and has emerged as a pressing issue for human health. A highly palmitoylated cluster of differentiation 36 (CD36) promotes free fatty acid (FFA) uptake, which contributes to the development of MASLD. Protocatechuic acid (PCA), the main metabolite of anthocyanins, was reported to inhibit MASLD by regulating the expression of CD36. However, the impact of PCA on CD36 palmitoylation has not been extensively studied. In the present study, we found that PCA could significantly reduce lipid uptake and accumulation in hepatocytes by decreasing CD36 palmitoylation. Inhibitors were used to prove that PCA suppressed CD36 palmitoylation by lowering zinc finger DHHC‐type palmitoyltransferase 5 (DHHC5) palmitoylation, but not in an acyl protein thioesterase 1 (APT1)‐dependent manner. Further experiments showed that PCA‐mediated inhibition of DHHC5 palmitoylation and acyltransferase activity was closely related to the reduction of the CD36/Fyn/Lyn complex. PCA diminished the palmitoylation of CD36 and DHHC5 and ultimately lessened lipid uptake and accumulation in hepatocytes.
Article
Background and purpose Chemotherapy with doxorubicin (DOX) is associated with toxicity in many organs including cardiac tissue. A large body of evidence has suggested that phenolic acids, such as protocatechuic acid (PCA), have beneficial effects on cardiovascular problems. This investigation was conducted to evaluate the ameliorative properties of PCA against DOX-induced cardiotoxicity in Wistar rats. Experimental approach Animals were treated with PCA (50, 100, and 200 mg/kg, orally) for 10 days. On the 7th day, a single injection of DOX (20 mg/kg/day, i.p.) was administered to induce cardiotoxicity. Electrocardiography, biochemical analysis of cardiac markers, and histological inspections were performed. Findings/Results Pretreatment with PCA, especially at the doses of 100 and 200 mg/kg for 7 days before the administration of DOX, significantly improved cardiac rhythm and pathological changes, reduced serum levels of creatine phosphokinase-MB, lactate dehydrogenase, aspartate aminotransferase, lipid peroxides and also prevented heart weight rise. Conclusions and implications The in-vivo findings of the current study revealed that PCA exhibits protective effects against DOX-induced cardiotoxicity. These results suggest that PCA, a natural phenolic acid, may serve as a promising candidate for cardioprotective interventions in clinical trials involving chemotherapy with DOX.
Article
Aim: Aronia melanocarpa is a red-purple medicinal fruit known for its therapeutic properties in the urinary system by anti-inflammatory effects with high antioxidant content. The aim of the study is to show the supportive effect of Aronia melanocarpa extract delayed toxicity on the bladder induced by cyclophosphamide (CYC) that an antineoplastic agent. Material and Methods: In the study three groups were constituted control (n=7), CYC(urotoxicity group, n=7) and CYC+ARONIA(treatment group, n=7). 100 mg/kg CYC intraperitoneally were given to CYC and CYC+ARONIA groups and waited for 4 weeks to be created delayed toxicity. At the end of the 4 weeks, 200 mg/kg Aronia melanocarpa was administered 15 times by oral gavage every other different day to CYC+ARONIA group (1 month in total). Sacrification was performed and after serum and urine samples were taken, the bladder was released from the sphincter region with curved-tipped forceps. Bladder tissues were investigated histologically. P38 mitogen activated preotein kinase (P38 MAPK), total antioxidant (TAS) and oxidant (TOS) status were evaluated in serum and urine samples. Results: In histology, histological damage in the bladder continued in the CYC group, while Aronia melanocarpa treatment caused healing in the bladder tissue in the CYC+ARONIA group. No difference was found between the groups in terms of P38 MAPK, TAS and TOS in serum and urine samples. Conclusion: According to the experimental results, the fact that Aronia melanocarpa extract improves the histological damage caused by CYC in the delayed period, and the serum and urine findings were the same as the controls, brought up the therapeutic effect of Aronia melanocarpa in urotoxicity.
Article
Full-text available
For some classes of dietary polyphenols, there are now sufficient intervention studies to indicate the type and magnitude of effects among humans in vivo, on the basis of short-term changes in biomarkers. Isoflavones (genistein and daidzein, found in soy) have significant effects on bone health among postmenopausal women, together with some weak hormonal effects. Monomeric catechins (found at especially high concentrations in tea) have effects on plasma antioxidant biomarkers and energy metabolism. Procyanidins (oligomeric catechins found at high concentrations in red wine, grapes, cocoa, cranberries, apples, and some supplements such as Pycnogenol) have pronounced effects on the vascular system, including but not limited to plasma antioxidant activity. Quercetin (the main representative of the flavonol class, found at high concentrations in onions, apples, red wine, broccoli, tea, and Ginkgo biloba) influences some carcinogenesis markers and has small effects on plasma antioxidant biomarkers in vivo, although some studies failed to find this effect. Compared with the effects of polyphenols in vitro, the effects in vivo, although significant, are more limited. The reasons for this are 1) lack of validated in vivo biomarkers, especially in the area of carcinogenesis; 2) lack of long-term studies; and 3) lack of understanding or consideration of bioavailability in the in vitro studies, which are subsequently used for the design of in vivo experiments. It is time to rethink the design of in vitro and in vivo studies, so that these issues are carefully considered. The length of human intervention studies should be increased, to more closely reflect the long-term dietary consumption of polyphenols.
Article
Full-text available
The transcription factor NF-kappaB has been the focus of intense investigation for nearly two decades. Over this period, considerable progress has been made in determining the function and regulation of NF-kappaB, although there are nuances in this important signaling pathway that still remain to be understood. The challenge now is to reconcile the regulatory complexity in this pathway with the complexity of responses in which NF-kappaB family members play important roles. In this review, we provide an overview of established NF-kappaB signaling pathways with focus on the current state of research into the mechanisms that regulate IKK activation and NF-kappaB transcriptional activity.
Article
Full-text available
Five different varieties of greek table olives (Kalamon, Tsakistes, Crete, Amfissas and Thrubes Crete) were investigated for the total polyphenol content and phenolic compounds, humidity, fat and total antioxidant capacity. Analysis was performed on the flesh and kernel of the table olives. Total polyphenol content was estimated with the Folin–Ciocalteau assay, humidity with freeze drying and total fat with Soxhlet extraction. Qualitative analysis of phenols and phenolic acids was performed with gas chromatography/mass spectrometry and thirteen compounds were identified in flesh as well in kernel except of oleanolic acid. Finally the antioxidant activity of olives was assessed by scavenging of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Total antioxidant capacity is in descending order: Tsakistes>Amfissas>Kalamon>Crete>Thrubes Crete. By the present work, the consumption of table olives, is considered to offer a high intake of antioxidants, mainly polyphenols, and so a health benefit for the prevention of many decadent diseases.
Book
This text is a comprehensive reference covering the chemistry, physiology, chemotaxonomy, biotechnology and food technology aspects of the anthocyanins. Topics discussed include types of anthocyanins, structural transformations, colour stabilization and intensification factors, biosynthesis and intensification factors, biosynthesis, analysis and functions of anthocyanins. An in-depth review of the literature discussing anthocyanins of fruits, cereals, legumes, roots, tubers, bulbs, cole crops, oilseeds, herbs, spices, and minor crops is included as well.
Article
Antioxidants have been shown to be effective in murine models of sepsis. Protocatechuic acid has antioxidant activity. In the present study, the protective effects of protocatechuic acid and its derivatives were investigated in a mouse model of septic shock induced by lipopolysaccharide (LPS)/D-galactosamine (GalN). Pretreatment of animals with protocatechuic acid effectively suppressed LPS/GalN-induced lethality; protocatechuic acid isopropyl ester was the most effective among the various derivatives of protocatechuic acid. Protocatechuic acid isopropyl ester was also effective in protection against the high-dose LPS-induced shock. Pretreatment with protocatechuic acid isopropyl ester effectively suppressed the LPS/GalN-induced increase in plasma tumor necrosis factor (TNF)-α alanine aminotransferase (ALT), nitrite/nitrate levels, and hepatic malondialdehyde levels. In contrast, it markedly enhanced the LPS/GalN-induced increase in plasma interleukin (IL)-10 levels, without any changes in IL-6 plasma levels. These results suggest that protocatechuic acid isopropyl ester could be useful for the prevention of sepsis.
Article
Many studies have suggested that dietary flavonoids are anticancer agents that induce the apoptosis of cancer cells. However, the effects of flavonoids on the induction of apoptosis in osteosarcoma cells are unclear. Previously, a flavonoid fraction, consisting mainly of protocatechuic acid, fustin, fisetin, sulfuretin, and butein, herein named RCMF (the RVS chloroform-methanol fraction), was prepared from a crude acetone extract of Rhus verniciflua Stokes (RVS). This study evaluated the effects of RCMF on the proliferation and apoptosis using human osteosarcoma (HOS) cells. The mechanism of growth inhibition of the HOS cells by the flavonoid fraction, RCMF, was also assessed. The results demonstrated that RCMF exhibited sensitive growth inhibition and induced apoptosis in HOS cells. PARP cleavage was closely associated with the RCMF-induced apoptosis of the HOS cells. Furthermore, the activation of caspase 8 and Bax, the inhibition of Bcl-2 expression, and the release of cytochrome c are believed to be involved in the RCMF-mediated apoptosis. Collectively, these findings suggest that RCMF is an agent which may be capable of inducing sensitive growth inhibition and apoptosis in HOS cells.
Article
We have clarified for the first time how cyanidin 3-O-β-D-glucoside (C3G), which is a potent antioxidant anthocyanin, is absorbed and metabolized in vivo. Rats were orally administered C3G (0.9 mmol/kg body weight), and C3G rapidly appeared in the plasma. However, the aglycon of C3G (cyanidin; Cy) was not detected, although it was present in the jejunum. Protocatechuic acid (PC), which may be produced by degradation of Cy, was present in the plasma and the concentration was 8-fold higher than that of C3G. These results suggest that plasma PC and C3G may contribute to the antioxidant activity of the plasma. In the liver and kidney, C3G was metabolized to methylated C3G (methyl-C3G), suggesting that C3G and/or methyl-C3G act as antioxidants in the tissues.
Chapter
Summary points l Although most biophenols have antioxidant properties, these properties alone may not account for all their beneficial effects. l Emerging findings suggest that biophenols have a variety of potential mechanisms of action in cytoprotection against oxidative stress, which may be independent of conventional antioxidant-reducing activities. l Such mechanisms might entail the interaction of biophenols with cell signaling, and influence gene expression, and hence modulate specific enzymatic activities that drive the intracellular response against oxidative stress. l We have demonstrated that biophenols contained in extra virgin olive oil induce an increased mRNA transcription of glutathione peroxidase and glutathione reductase genes in murine macrophages. l As a consequence, glutathione is preserved from consumption and the endogenous antioxidant defenses are strengthened. l The molecular mechanism responsible for the modulation of gene expression by EVOO biophenols is likely to involve the activation of ARE/EpRE obtained through the activation of the Nrf2 pathway.
Article
Protocatechuic acid (= 3,4-dihydroxybenzoic acid; 1) exhibits a significantly slow DPPH (= 2,2-diphenyl-1-picrylhydrazyl) radical-scavenging reaction compared to its esters in alcoholic solvents. The present study is aimed at the elucidation of the difference between the radical-scavenging mechanisms of protocatechuic acid and its esters in alcohol. Both protocatechuic acid (1) and its methyl ester 2 rapidly scavenged 2 equiv. of radical and were converted to the corresponding o-quinone structures 1a and 2a, respectively (Scheme). Then, a regeneration of catechol (= benzene-1,2-diol) structures occurred via a nucleophilic addition of a MeOH molecule to the o-quinones to yield alcohol adducts 1f and 2c, respectively, which can scavenge additional 2 equiv. of radical. However, the reaction of protocatechuic acid (1) beyond the formation of the o-quinone was much slower than that of its methyl ester 2. The results suggest that the slower radical-scavenging reaction of 1 compared to its esters is due to a dissociation of the electron-withdrawing carboxylic acid function to the electron-donating carboxylate ion, which decreases the electrophilicity of the o-quinone, leading to a lower susceptibility towards a nucleophilic attack by an alcohol molecule.