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Biological Activities of Plant Pigments Betalains

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Abstract Betalains are a family of natural pigments present in most plants of the order Caryophyllales. They provide colors ranging from yellow to violet to structures that in other plants are colored by anthocyanins. These include edible fruits and roots but also flowers, stems, and bracts. The recent characterization of different bioactivities in experiments with betalain-containing extracts and purified pigments has renewed the interest of the research community in these molecules used by the food industry as natural colorants. Studies with multiple cancer cell lines have demonstrated a high chemopreventive potential that finds in vitro support in a strong antiradical and antioxidant activity. Experiments in vivo with model animals and bioavailability studies reinforce the possible role played by betalains in the diet. This work provides a critical review of all the claimed biological activities of betalains, showing that the bioactivities described might be supported by the high antiradical capacity of their structural unit, betalamic acid. Although more investigations with purified compounds are needed, the current evidences suggest a strong health-promoting potential.
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Biological Activities of Plant
Pigments Betalains
FERNANDO GAND
IA-HERRERO, JOSEFA ESCRIBANO and
FRANCISCO GARC
IA-CARMONA
Departamento de Bioqu
ımica y Biolog
ıa Molecular A, Unidad Docente de Biolog
ıa, Facultad de Veterinaria,
Regional Campus of International Excellence “Campus Mare Nostrum,” Universidad de Murcia, Espinardo,
Murcia, Spain
Betalains are a family of natural pigments present in most plants of the order Caryophyllales. They provide colors ranging
from yellow to violet to structures that in other plants are colored by anthocyanins. These include not only edible fruits and
roots but also flowers, stems, and bracts. The recent characterization of different bioactivities in experiments with betalain
containing extracts and purified pigments has renewed the interest of the research community in these molecules used by
the food industry as natural colorants. Studies with multiple cancer cell lines have demonstrated a high chemopreventive
potential that finds in vitro support in a strong antiradical and antioxidant activity. Experiments in vivo with model animals
and bioavailability studies reinforce the possible role played by betalains in the diet. This work provides a critical review
of all the claimed biological activities of betalains, showing that the bioactivities described might be supported by the high
antiradical capacity of their structural unit, betalamic acid. Although more investigations with purified compounds are
needed, the current evidences suggest a strong health-promoting potential.
Keywords Antiradical, biological activity, cancer, diet, review
INTRODUCTION
Betalains are water-soluble, nitrogen containing pigments
present in most plants of the order Caryophyllales. These are
divided into two groups: the violet betacyanins and the yellow
betaxanthins. Betacyanins present absorbance spectra centered
at wavelengths of around λ
m
D536 nm. Glycosylation and
acylglycosilation of one or two hydroxyl groups are possible
in betacyanins, and complex pigment structures can be
obtained (Heuer et al., 1994; Strack et al., 2003; Cai et al.,
2005). In contrast, betaxanthins are yellow and no glycosyla-
tion has ever been reported. The absorbance spectra of betax-
anthins are centered at wavelengths of around λ
m
D480 nm.
Both groups share betalamic acid as the structural and chro-
mophoric unit. It is condensed with amines and amino acids in
betaxanthins and with cyclo-DOPA in betacyanins (Gand
ıa-
Herrero et al., 2010a). Figure 1 shows the structures for beta-
lamic acid, the betacyanins aglyca (betanidin), and the general
structure for betaxanthins. The structure for the dopamine-
derived betaxanthin (miraxanthin V) is shown and compared
with other known bioactive metabolites such as resveratrol
and the anthocyanidin cyanidin.
Betalains are found not only in edible parts of plants but
also in leaves (Wang et al., 2007), flowers (Gand
ıa-Herrero
et al., 2009b), stems (Schliemann et al., 1996), and bracts
(Heuer et al., 1994). Anthocyanins and betalains are mutually
exclusive and have never been found together in the same
plant (Stafford, 1994; Brockington et al., 2011); in Caryophyl-
lales only the coloration of the Caryophylaceae and Mollugi-
naceae is due to anthocyanins. Among the Caryophyllales
plants, red beet roots (Beta vulgaris) (Hempel and B
ohm,
1997), the fruits of cacti belonging to the genus Opuntia
(mainly Opuntia ficus indica) (Felker et al, 2008; Osorio-
Esquivel et al., 2011), the dragon fruits from Hylocereus cacti
(mainly Hylocereus polyrhizus) (Wybraniec and Mizrahi,
2002; Wybraniec et al., 2007), and the Swiss chard (Beta vul-
garis) (Kugler et al., 2004) are known edible sources of beta-
cyanins and betaxanthins. Less common sources are the ulluco
tubers (Ullucus tuberosus) (Svenson et al., 2008), fruits of
Eulychnia cacti (Masson et al., 2011), and the berries from
Address correspondence to Dr. Fernando Gand
ıa-Herrero, Departamento
Bioqu
ımica y Biolog
ıa Molecular A, Unidad Docente de Biolog
ıa, Edificio
Facultad de Veterinaria, Universidad de Murcia, E-30100 Espinardo, Murcia,
Spain. E-mail: fgandia@um.es
Color versions of one or more of the figures in the article can be found
online at www.tandfonline.com/bfsn
Critical Reviews in Food Science and Nutrition, 56:937–945, (2016)
Copyright c
OTaylor and Francis Group, LLC
ISSN: 1040-8398 / 1549-7852 online
DOI: 10.1080/10408398.2012.740103
937
Rivina humilis (Khan et al., 2012). Certain Amaranthus spe-
cies are also consumed as cooked or fresh (Amin et al., 2006;
Sang-Uk et al., 2009). Betalain containing beetroot extracts
are used as the additive 73.40 in the 21 CFR section of the
Food and Drug Administration (FDA) in the United States and
under the E-162 code in the European Union to give a pink or
violet color to foods and beverages (Mart
ınez et al., 2006; Pru-
dencio et al., 2008; Junqueira-Goncalves et al., 2011; Gand
ıa-
Herrero et al., 2012b). Figure 2 shows pictures of edible prod-
ucts containing betalains. New colorants derived from Opuntia
fruit extracts (Mosshammer et al., 2006; Ob
on et al., 2009;
Sa
enz et al., 2009) or containing individual pigments (Gand
ıa-
Herrero et al., 2010b) have been also proposed. The joint pres-
ence of betaxanthins and betacyanins in the same parts of
plants generates orange to red shades depending on the pig-
ment proportion (Schliemann et al., 2001; Kugler et al., 2004;
Gand
ıa-Herrero et al., 2005; Felker et al., 2008). Due to their
hydrophilic nature, betalains are accumulated in the vacuoles
of the cells that synthesize them, mainly in epidermal and sub-
epidermal tissues of plants (Wink, 1997). Interestingly, fungi
of the genera Amanita and Hygrocybe (von Ardenne et al.,
1974; Musso, 1979; Stintzing and Schliemann, 2007; Babos
et al., 2011) produce betalain-related pigments.
In recent years, betalains have shown promising bioactive
potential. Early investigations revealed a strong free radical
scavenging capacity of betalains purified from beetroot (Escri-
bano et al., 1998; Pedre~
no and Escribano, 2001). Subsequent
research revealed the existence of an intrinsic activity present
in all betalains that is modulated by structural factors (Cai
et al., 2003; Gand
ıa-Herrero et al., 2010a). Studies with
different cell lines have demonstrated the potential of betalains
in the chemoprevention of cancer (Wu et al., 2006; Sreekanth
et al., 2007), and experiments in vivo have shown that very
low concentrations of dietary pigments inhibit the formation
of tumors in mice (Kapadia et al. 2003; Lechner et al., 2010).
In humans, the plasma concentration of betalains after inges-
tion is sufficiently high to promote their incorporation into
low-density lipoprotein (LDL) and red blood cells, protecting
them from oxidative damage and hemolysis (Tesoriere et al.
2003, 2005). However, most of the biological activities
described have been reported according to studies with plant
extracts with limited or no pigment purification. Although
these studies are useful in identifying potential activities, iso-
lated compounds are necessary to link the effects described
Figure 1 Structures for betalamic acid, the betacyanins aglyca (betanidin), and the general structure for betaxanthins. R
1
and R
2
are side residues present in
amines or amino acids. For comparative purposes, the structure for the diphenolic betaxanthin Miraxanthin V is also shown together with resveratrol and
cyanidin.
Figure 2 Pictures of the best known sources of betalains: (A) Opuntia ficus-
indica fruit, and (B) Beta vulgaris root. (C) An encapsulated commercial col-
orant based on B. vulgaris root extracts, and (D) a dairy product containing B.
vulgaris extracts.
938 F. GAND
IA-HERRERO ET AL.
with the structures responsible. In this work, the biological
activities of betalains are exhaustively reviewed, considering
in vitro and in vivo experiments developed since the early
description of its free radical scavenging activity more than a
decade ago.
ACTIVITIES IN VITRO
Free Radical Scavenging and Antioxidant Activities
Since the introduction of a feasible technology to determine
the free radical scavenging potential of molecules and extracts
by the Rice-Evans group (Re et al., 1999), the ABTS (2,2’-azi-
nobis-(3-ethylbenzothiazoline-6-sulfonic acid)) radical assay
has become a standard technique in the evaluation of this
activity. In betalains, the ABTS radical assay has gained rele-
vance with respect to other similar methodologies such as the
DPPH (2,2-diphenyl-1-picrylhydrazyl) radical assay (Brand-
Williams et al., 1995) and the Oxygen Radical Absorbance
Capacity (ORAC) assay (Ou et al., 2001), or the direct reduc-
tion of Fe(III) to Fe(II) through the Ferric Reducing Antioxi-
dant Power (FRAP) assay (Benzie and Strain, 1996). This is
due to the use of a fully aqueous medium, the possibility of pH
variation, and the lack of signal interferences with fluorescent
probes. Antioxidant and antiradical concepts are frequently
not differentiated in the literature. It can be considered that
antiradicals or radical scavengers are antioxidant molecules
measured experimentally in the reduction of a radical. In this
section the term antiradical will be used when the activity has
been assessed through a radical-based assay (ABTS, DPPH, or
ORAC) independent of the original terms used by the authors.
The antioxidant term will be restricted to experiments not
involving stable radicals.
The first investigations that demonstrated a radical scaveng-
ing capacity in betalains were carried out separately with beta-
cyanins and betaxanthins, extracted from Beta vulgaris
(Escribano et al., 1998). Other works demonstrated activities
in betalains purified from different sources: Opuntia ficus-ind-
ica (Butera et al., 2002), B. vulgaris roots grown under axenic
conditions (Pavlov et al., 2002), and plants from Amarantha-
ceae (Cai et al., 2003). In all cases the radical scavenging
activity determined was higher than that detected for other
well-known compounds such as ascorbic acid, catechin, and
Trolox. Glucosylation from betacyanins was demonstrated to
reduce the activity of pigments (Cai et al., 2003) due to the
blockage of one of the hydroxyl groups. However, the pres-
ence of these groups is not necessary to express activity, in
contrast to the results obtained for flavonoids, where the
absence of activity has been described in dehydroxylated com-
pounds trans-chalcone, flavone, flavanone, and isoflavone
(Cai et al., 2006). Thus, an “intrinsic activity” exists in all
betalains studied, which can be enhanced by the presence of
hydroxyl groups, with an increase in terms of Trolox Equiva-
lent Antioxidant Capacity (TEAC) from 2.5 units to 4.0 units
for one hydroxyl group and to 5.8 units for two hydroxyl
groups (Gand
ıa-Herrero et al., 2009a). The last value is higher
than those found for other well-known antioxidants such as
epigallocatechin gallate (EGCG) present in green tea (Rice-
Evans et al., 1996; Stewart et al., 2005). Betalamic acid is the
simplest structure with betalain properties and it also possesses
antiradical and antioxidant activities, with a TEAC value of
2.7 units (Gand
ıa-Herrero et al., 2012a). Thus, betalamic acid
can be considered as the bioactive unit of these pigments
(Fig. 1). Structure–activity relationships in betalains show that
the antiradical activity for the simplest pigments is enhanced
by the connection of the betalain characteristic electron reso-
nance system with an aromatic ring, thus increasing the TEAC
value by 0.4 units. If this is done to form indoline-like sub-
structures, similar to those present in betacyanins, the
enhancement is higher, increasing the TEAC value by
1.6 units (Gand
ıa-Herrero et al., 2010a).
Although the actual contribution of individual pigments is
difficult to be established, the free radical scavenging activity
of betalain containing extracts has been determined in several
cases. The fruits of cactus Hylocereus polyrhizus have
revealed a strong free radical scavenging activity that was
higher in peel extracts than in those obtained from flesh, con-
sistent with a higher content of betalains and flavonoids in the
peel (Wu et al., 2006). Multiple clones of Opuntia plants
showed that the TEAC values for cactus juices were close to
those of red wine and green tea infusions (Stintzing et al.,
2005). In addition to O. ficus-indica, recent attention has been
focused on the fruits of other edible species like O. joconostle
and O. macrorhiza (Moussa-Ayoub et al., 2011; Osorio-Esqui-
vel et al., 2011; Morales et al., 2012). A complex profile of
bioactive substances, including betalains, has been described
in these species, with extracts showing high antiradical and
antioxidant activities. When purified betalain fractions were
obtained, these exhibited higher activity than the flavonoid
and phenolic containing fractions obtained from the same
fruits (Osorio-Esquivel et al., 2011). Betalains from Rivina
humilis were also partially purified and the activity of betacya-
nin- and betaxanthin-rich fractions were assayed (Khan et al.,
2012). This confirmed both antiradical and antioxidant activi-
ties of the pigments and explained the antiradical effect
detected in fruit extracts. In the case of B. vulgaris, extracts
from hairy root cultures have revealed a higher radical scav-
enging potential than intact plants. It has been proposed that
this is due to an increased concentration of phenolic com-
pounds, which may have a synergistic effect with betalains
(Georgiev et al., 2010).
The redox properties of betalains have been studied by
cyclic and differential pulse voltammetry. Reduction poten-
tials were determined for purified indicaxanthin and betanin,
and were higher in the case of the betacyanin (Butera et al.,
2002). Strong antioxidant and antiradical betanin activities
have been properly explained in terms of its electron donor
capacity, calculating the bond dissociation energy and the ioni-
zation potential of the molecule (Gliszczy
nska-
Swiglo et al.,
BIOLOGICAL ACTIVITIES OF PLANT PIGMENTS BETALAINS 939
2006). This explains the marked pH dependence found in free
radical scavenging experiments. Increased pH values imply
higher activity and higher TEAC values not only in the case of
betanin. A comparative study with 15 natural and synthetic
betalains showed a common trend in the pH dependence of the
free radical scavenging activity (Gand
ıa-Herrero et al.,
2010a). This indicates the existence of a relevant deprotona-
tion equilibrium in the expression of the activity and common
to all betalains. The same tendency was found for free betala-
mic acid, and it has been linked to its nucleophilic capacity,
determining a pK
a
value of 6.8 (Gand
ıa-Herrero et al., 2012a).
A similar pH dependence of the free radical scavenging activ-
ity has been described for flavonoids. Deprotonation generates
a phenolate anion in these molecules, which is a better electron
donor and, thus, a more effective scavenger (Madsen et al.,
2000; Muzolf et al., 2008).
Relatedtotheirspectroscopic properties and to their
redox capacity to transfer electrons, betalains have been
used as natural dyes in dye-sensitized solar cells (Zhang
et al., 2008). These are one of the most promising devices
for solar energy conversion due to their reduced production
cost and low environmental impact (Narayan, 2012). The
technology has been assayed with betalain containing
extracts of Beta vulgaris roots (Zhang et al., 2008; Calo-
gero et al., 2010), Hylocereus fruits (Ali and Nayan, 2010),
Opuntia fruits (Calogero et al., 2010; Calogero et al.,
2012), and Bouganvillea bracts (Calogero et al., 2010; Her-
nandez-Martinez et al., 2011). While dye-sensitized solar
cells containing anthocyanins and carotenoids as dyes have
shown overall solar energy conversion efficiencies below
1%, betalain containing cells obtain conversion efficiencies
of up to 1.7% under simulated sunlight conditions, which
is comparable to that of natural photosynthesis (Calogero
et al., 2009; Calogero et al., 2010; Zhou et al., 2011). On
optimizing the performance of solar cell and using purified
betanin instead of raw extracts, the energy conversion effi-
ciencies of the cells have recently been raised to 2.7%
(Sandquist and McHale, 2011; Calogero et al., 2012).
Other Activities In vitro
In addition to their potent antioxidant and free radical scav-
enging activities, and probably in relation with them, the beta-
cyanins betanin and betanidin isolated from B. vulgaris were
able to inhibit the peroxidation of linoleic acid and the oxida-
tion of LDL. The effect was higher than that detected for other
known antioxidants such as a-tocopherol and catechin (Kanner
et al., 2001). These activities were assessed considering differ-
ent oxidizers on linoleic acid emulsions and the oxidative sus-
ceptibility of human LDL obtained from healthy volunteers
and microsomes obtained from turkey muscle tissue. Purified
betalains have been also reported to be scavengers of hypo-
chlorous acid, which is the most powerful oxidant produced
by human neutrophils in inflammatory processes and to
interfere with the activity of myeloperoxidase enzyme respon-
sible for its formation (Allegra et al., 2005).
Although the molecules responsible for plant pigmentation
seem to be erroneously identified (Kugler et al., 2004), aque-
ous extracts of Swiss chard (B. vulgaris) containing betalains
were demonstrated to possess inhibitory activity on the
enzyme acetylcholinesterase (Sacan and Yanardag, 2010).
This enzyme is involved in the processes of neurotransmission
by cleaving the neurotransmitter acetylcholine and its inhibi-
tion has been demonstrated to have therapeutic potential in the
treatment of neurological disorders, including Alzheimer’s
disease (Orhan, 2012).
STUDIES WITH CELLS
Recent research with different cancer cell lines has demon-
strated a high chemopreventive potential of betalain contain-
ing extracts. The use of purified pigments in some of the
studies justifies the activities assessed and reinforces the bio-
logical potential of betalains. Extracts of Beta vulgaris have
shown high chemopreventive effect in the induced Epstein–
Barr early antigen activation assay in vitro using a cell line
from lymphoma (Kapadia et al., 1996). Extracts significantly
reduced cells’ viability, with the effect being ascribed to beta-
lains. The activity was compared with other plant extracts,
including an anthocyanin-rich cranberry extract, exhibiting
maximum activity. A limited cytotoxicity of B. vulgaris
extracts has also been demonstrated for human prostate and
breast cancer cell lines (Kapadia et al., 2011).
Extracts obtained from Opuntia ficus-indica proved to be
an effective growth inhibitor and apoptosis inductor in sev-
eral cell lines of immortalized ovarian and cervical epithelial
cells and ovarian, cervical, and bladder cancer cells (Zou
et al., 2005). The effect of the cactus pear solution was dose-
and time-dependent. Cactus extracts were able to inhibit
growth of cancer cells and affect their morphology with con-
centrations of 5% of fruit extract in cell culture. A higher
concentration was necessary (10–25%) for apoptotic effect.
However, the use of raw extracts avoided the identification of
active compounds. Betalains from the berries of Rivina
humilis were tested regarding their effect on hepatocellular
carcinoma cells (Khan et al., 2012). In this case, the betalains
were partially purified and betaxanthins and betacyanins sep-
arately showed dose-dependent cytotoxicity after 24 and
48 hours respectively.
Extracts from the fruit of the cactus Hylocereus polyrhizus
revealed an inhibitory activity of growth of melanoma cancer
cells (Wu et al., 2006). The inhibition was dose-dependent
and higher in peel than in flesh extracts, in relation with a
higher content of flavonoids and betalains. Remarkably, in the
same experiment pure betanin was assayed, revealing a strong
inhibition of the proliferation of melanoma cancer cells. Pure
betanin was also used against a human chronic myeloid leuke-
mia cell line in a different study (Sreekanth et al., 2007). The
940 F. GAND
IA-HERRERO ET AL.
addition of betanin implied the inhibition of cell growth in a
dose-dependent manner with an IC
50
of 40 mM after 24 hours
of incubation. Betanin enters the cells and alters the mitochon-
drial membrane integrity. This ultimately leads to the activa-
tion of caspases and nuclear disintegration. The biochemical
alterations were reflected in morphological changes in cells,
which were followed by scanning and transmission electron
microscopy and flow cytometry. Cells entered apoptosis, in a
clear in vitro demonstration of anti-cancer potential of
betalains. Table 1 summarizes all the studies developed with
betalains, which involved cancer cells, identifying the corre-
sponding cell lines.
In addition to the effect on cancer cell lines, B. vulgaris
extracts have been found to dose-dependently suppress the
degradation of tryptophan and the production of neopterin in
human peripheral blood mononuclear cells involved in the
inflammatory response (Winkler et al., 2005). Cells were
obtained from healthy donors and stimulated in the presence
of the betalain containing extracts. The cell response was
reduced by the presence of extracts, suggesting that the B. vul-
garis juice possesses compounds with immunosuppressive and
anti-inflammatory activities. Human red blood cells also
showed increased resistance to hemolysis when they were
incubated with growing concentrations of purified indicaxan-
thin and betanin in vitro (Tesoriere et al., 2005). Furthermore,
LDLs isolated from healthy humans have been demonstrated
to incorporate purified indicaxanthin and betanin after ex vivo
incubation (Tesoriere et al., 2003). LDLs enriched with the
pigments were more resistant than native LDLs to copper-
induced oxidation, with indicaxanthin being more effective
than betanin in the protection from oxidative damage.
STUDIES WITH ANIMALS
In vivo anti-tumor formation activity in mouse skin has
been demonstrated for Beta vulgaris extracts. The extracts
were orally administered to the animals in drinking water after
topical tumor induction (Kapadia et al., 1996). Results showed
a significant decrease in the incidence and number of papillo-
mas found in the mice skin. In the same study, lung tumor for-
mation was induced to mice, and inhibited by the oral
administration of B. vulgaris extracts. A 60% reduction in the
number of mice with adenomas was observed, with an addi-
tional 30% reduction in the number of tumors for the affected
animals. Skin tumor formation induced chemically and pro-
moted by ultraviolet (UV)-based light was also inhibited after
the oral administration of B. vulgaris extracts in mice (Kapadia
et al., 2003). In addition, animals that followed the treatment
also showed a reduced splenomegaly. In the case of induced
tumors in the liver, oral administration of beet extract reduced
the tumor incidence to 40%, showing a potent cancer chemo-
preventive activity in the model animals.
Analogously, chemoprevention against induced esophageal
carcinogenesis was also demonstrated in rats for B. vulgaris
extracts administered orally (Lechner et al., 2010). Results
showed a reduction of 45% in the number of papillomas, limit-
ing cell proliferation, angiogenesis, and inflammation. It was
hypothesized that betalains antioxidant activity reduced the
level of reactive oxygen species to levels that were too low to
stimulate the anomalous proliferation.
In addition, dose-dependent protection of the adverse
effects of g-ray irradiation in rats has been demonstrated in
vivo for Beta vulgaris extracts, and the effect has been
ascribed to betalains (Lu et al., 2009). Orally administered
extracts partially restored the normal biochemical levels of the
altered parameters caused by irradiation, including catalase,
superoxide dismutase, and lipid oxidation activities in liver,
spleen, and kidney. Furthermore, the prevention of decline in
the spleen and thymus index in irradiated mice led the authors
to suggest that betalains could partially restore the immuno-
logical function and improve the pathological status in vivo.
Although the effect of betalains cannot be identified, aque-
ous extracts of Opuntia ficus-indica were able to inhibit tumor
Table 1 Studies with betalain containing extracts involving cancer cells. The cell line identification, the source of betalains, the use of purified pigments, and the
corresponding references are shown in each case
Cell line Betalains source Effect Pigment purification References
Raji (lymphoma, human) Beta vulgaris Reduced cell viability No Kapadia et al., 1996
IOSE (ovarian epithelium, human) Opuntia ficus-indica Growth inhibition No Zou et al., 2005
OVCA420 (ovarian cancer, human) Opuntia ficus-indica Growth inhibition, apoptosis induction No Zou et al., 2005
SKOV3 (ovarian cancer, human) Opuntia ficus-indica Growth inhibition, apoptosis induction No Zou et al., 2005
TCL-1 (cervical epithelium, human) Opuntia ficus-indica Growth inhibition, apoptosis induction No Zou et al., 2005
HeLa (cervical cancer, human) Opuntia ficus-indica Growth inhibition, apoptosis induction No Zou et al., 2005
Me180 (cervical cancer, human) Opuntia ficus-indica Growth inhibition, apoptosis induction No Zou et al., 2005
UM-UC-6 (bladder cancer, human) Opuntia ficus-indica Growth inhibition No Zou et al., 2005
T24 (bladder cancer, human) Opuntia ficus-indica Growth inhibition, apoptosis induction No Zou et al., 2005
B16F10 (melanoma, mouse) Hylocereus polyrhizus Growth inhibition No Wu et al., 2006
B16F10 (melanoma, mouse) Unspecified (commercial) Growth inhibition Purified betanin Wu et al., 2006
K562 (leukemia, human) Opuntia ficus-indica Growth inhibition, apoptosis induction Purified betanin Sreekanth et al., 2007
PC-3 (prostate cancer, human) Beta vulgaris Growth inhibition No Kapadia et al., 2011
MCF-7 (breast cancer, human) Beta vulgaris Growth inhibition No Kapadia et al., 2011
HepG2 (liver cancer, human) Rivina humilis Reduced cell viability Partial Khan et al., 2012
BIOLOGICAL ACTIVITIES OF PLANT PIGMENTS BETALAINS 941
growth in a nude mouse of ovarian cancer model compared
with untreated animals (Zou et al., 2005). The extract was
administered by injection and compared with the chemo-
preventive agent N-(4-hydroxyphernyl) retinamide (4-HPR),
used in ovarian cancer clinical trials. Both cactus pear extracts
and chemopreventive agent reduced the tumor size in a com-
parable manner. Opuntia fruits’ extracts have also demon-
strated their potential in the protection and recovery of the
liver after damage has been induced. Hepatotoxicity by carbon
tetrachloride (CCl
4
) in rats was limited in animals fed with the
betalain containing extracts both after and before the damag-
ing treatment (Galati et al., 2005). The oral administration of
the extract promoted liver recovery at histochemical and bio-
chemical levels. The same effect was described for betalain
containing extracts of whole plants of Amaranthus spinosus,
and it has been proposed that the mechanism of hepatoprotec-
tion was due to its antioxidant activity (Zeashan et al., 2008,
2009).
Interestingly, other activities have been also described for
betalains. Purified pigments extracted from Portulaca olera-
cea have demonstrated their capacity to reverse induced learn-
ing and memory impairments produced by D-galactose in
mice (Wang and Yang, 2010). In comparison with ascorbic
acid, orally administered betalains showed a more pronounced
effect in ameliorating cognition deficits in mice and restored
the normal biochemical levels of relevant enzymes, being
proposed a neuroprotective effect. Extracts of Amaranthus spi-
nosus and Boerhaavia erecta containing betalains have dem-
onstrated antimalarial activity in an in vivo model assay in
mice (Hilou et al., 2006). The aqueous extracts were able to
inhibit the growth of inoculated parasites in a dose-dependent
manner. These plants are used in the traditional medicine
against Plasmodium falciparum infections (malaria) in
humans. The authors pointed to betacyanins betanin and amar-
anthin as possible molecules responsible for the assessed activ-
ity at the same time that they acknowledged the need to
perform experiments with purified compounds. Opuntia ficus-
indica extracts and its main pigment, indicaxanthin, in a pure
form were demonstrated to reduce the contractility of the ileal
longitudinal muscle obtained from mice (Baldassano et al.,
2010, 2011). The authors propose the usefulness of the finding
in the regulation of intestinal motility in related disorders and
describe the mechanism of action. It implies the inhibition of
phosphodiesterase enzymes and the increase in cAMP levels,
which lead to a decrease in intracellular Ca
2C
concentration,
which ultimately promotes the smooth muscle relaxation.
Bioavailability studies of betalains after oral administration
in humans indicate that model betalains, betanin, and indicax-
anthin remain in the body and are able to play a health-promot-
ing function, thereby improving the body redox status
(Tesoriere et al., 2004; Frank et al., 2005). Maximum plasma
concentrations are reached three hours after consumption,
with a decline corresponding to first-order kinetics. After this
time period, betalains can be incorporated into the red cells in
vivo (Tesoriere et al., 2005). They are completely eliminated
after 12 hours of ingestion, with a urinary excretion of 76% in
the case of betaxanthin, but highly limited in the case of beta-
nin. This indicates metabolization of the pigment and its trans-
formation to other compounds, including betalamic acid, as
demonstrated in simulated digestion studies (Pavlov et al.,
2005; Tesoriere et al., 2008). However, the inability of part of
the population to metabolize betanin has also been described,
excreting it to a high level in urine. This is known as beeturia,
and although its mechanism is not well understood, its inci-
dence is high in iron-deficient subjects (Watson et al., 1963;
Sotos, 1999; Mitchell, 2001).
CONCLUSIONS
The description of the betalains free radical scavenging
activity implied the renaissance of interest in these molecules
by the research community. Since then, multiple articles with
claims regarding the biological activity of betalains have been
published, including studies on the chemoprevention of tumor
formation. Considering their demonstrated safety (Schwartz
et al., 1983; Khan et al., 2011), the recent bibliography indi-
cates the potential of betalains for food, pharmaceutical, and
cosmetic industries.
Promising results have been reported for tumor prevention
in vivo and the possible role played by betalains in the diet.
However, the use of extracts limits the conclusions drawn, the
hypothesis on the mechanisms involved, and the therapeutic
potential of the assays. Currently, studies with purified pig-
ments are scarce but they provide exciting conclusions.
Increasing of these studies would help to establish the actual
role played by betalains alone or in cooperation with other
compounds. Caution must be taken regarding the possible
application of biological activities described in natural mole-
cules, but the results for betalains are promising in terms of
their health-promoting potential.
FUNDING
The authors acknowledge the financial support of Ministerio
de Ciencia e Innovaci
on (MICINN, FEDER, Spain, project
AGL2011-25023 and AGL2014-57431) and Fundaci
on
Se
oneca, Agencia de Ciencia y Tecnologia de la Regi
on de
Murcia (Plan Regional de Ciencia y Tecnologia 2007/2010,
Programa de Ayudas a Grupos de Excelencia de la Regi
on de
Murcia). F. Gand
ıa-Herrero has a contract with the “Programa
Ram
on y Cajal” (MICINN, FEDER, Spain).
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tion. Nutr. J.4:25.
BIOLOGICAL ACTIVITIES OF PLANT PIGMENTS BETALAINS 945
... Betalains are water-soluble nitrogen-containing pigments present in most plants of the order Caryophyllales, which are synthesized from the amino acid tyrosine into two structural groups: the red-violet betacyanins and the yellow-orange betaxanthins. These pigments are composed of a nitrogenous core of betalamic acid, which can either condense with amines to form betaxanthins or with imino compounds to form betacyanins (69,78,79). The strength of these colorants is three times higher than anthocyanins (5). ...
... In addition, betalains have been associated with several biological activities such as anti-inflammatory, antiproliferative, antimicrobial activities, and free radical scavenging potential, among others. This was demonstrated through in vivo studies, which indicate that betalain supplementations could play a beneficial role in diseases such as hypertension, cancer and dyslipidemia (69,79,80). ...
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Ultrasound is an emerging technology, which has been highly explored in the food area to improve processes and products. When ultrasound is applied to a product with solid or fluid characteristics, the passage of acoustic waves and acoustic cavitation generates different mechanisms responsible for modifications in the original matrix of the sample. These effects of ultrasound can also be used to take advantage of by-products, for example by extracting compounds of interest, including natural pigments. Natural pigments or colorants are being highly demanded by different industries not only for color purposes but also due to their healthy properties, the greater demands in regulations and new consumer preferences. This review presents an updated critical analysis of the application of ultrasound-assisted extraction (UAE) to obtain natural pigments from food processing by-products. Initially, the ultrasound effects and mechanisms that improve the extraction of natural pigments in a fluid medium, as well as the factors that influence the extraction and the energy consumption of UAE are analyzed and described. Subsequently, the UAE application to obtain pigments belonging to the groups of carotenoids, chlorophyll, anthocyanins and betalains is evaluated. These sections detail the processing conditions, positive and negative effects, as well as possible applications of the extracted pigments. This review presents relevant information that may be useful to expand and explore new applications of ultrasound technology as well as promote the revaluation of by-products to obtain pigments that can be used in food, pharmaceutical or cosmetic industries.
... Combination of the two pigments in various ratios yields intermediate hues [8,9]. Betalains have been considered as a current food coloring trend also due to their health beneficial effects [10]. Significantly, the biological activity of betalains seem to play an essential role in human health due to their robust antioxidant ability and their capacity to scavenge free radicals [11][12][13][14] . ...
... Betalain extracts usually contain numerous polyphenols, including flavonoids and phenolic acids. These polyphenols contribute to the antioxidant activity of these extracts [10]. Therefore, the quantification of the total phenolic content is important, to determine the antioxidant potency of the isolated extracts. ...
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Replacing synthetic dyes with natural pigments has gained great attention over the past years in the food industry, due to the increased alertness of consumers for nontoxic and natural additives. Betalains are water-soluble nitrogenous natural pigments that are used as natural colorants in food industries, due to their applicability and their rich pharmacological profile including antioxidant, antimicrobial, and anticancer properties. Therefore, there is a need for a detailed exploration of betalains to fully exploit their properties. Opuntia spp. plants are one of the primary sources of betalains. The objective of this study was to identify betalain phytochemical content in prickly pear cactus of two different Opuntia species from Greece (an Opuntia ficus-indica (L.) Mill (OFI) orange prickly pear cultivar and an Opuntia spp. purple prickly pear cultivar) using modern analytical techniques as also to evaluate their antioxidant and cytotoxicity profile. To achieve this we used an array of analytical techniques, including ultra-violet-vis (UV-Vis) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and liquid chromatography-high resolution mass spectrometry (LC-HRMS) as also cell based in vitro assays. These enabled us to establish a rapid approach that can distinguish the different Opuntia spp. cultivars based on their phytochemical constituents through untargeted metabolomics analysis using ultra-high performance liquid chromatography-mass spectrometry - quadrupole time-of-flight (UPLC/MS Q-TOF). These findings could allow a further exploitation of Opuntia species and especially their enriched betalain phytochemical profile as viable source of natural food colorants.
... The betalain content of red beet was an average of 101.53 mg 100 g -1 at the beginning, and a drastic reduction was seen in samples in the 1st month of storage, up to 28%, while it was almost stable in the 2nd and 3rd months (Table 4). This drop was reported to be a cause of enzymatic degradation including peroxidase activity (Pedreño and Escribano 2001) and instability of betalains in red beets (Gandía-Herrero et al. 2016). The same direction of changes in betalain content was corroborated by the result of pH increase. ...
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Red beet has a high metabolic rate, and its storability is limited by detrimental quality changes during storage. One of the solutions that can reduce these changes and provide commercial attractiveness is fertilization at preharvest. The other pivotal one is cold storage to meet marketing schedules. Thus, the objective of the study is to investigate the effects of nitrogen and boron fertilization on quality traits of red beet under storage conditions. For this purpose, combined nitrogen (200 kg ha⁻¹) and boron (1000 mL ha⁻¹) fertilization were applied, and non-fertilized groups were considered as control. Subsequently, harvested whole red beets were stored at 0 °C and 4 °C with 95 ± 2% relative humidity for 3 months. The red beets were analyzed for their weight loss, respiration rate, color characteristics, dry matter, pH, SSC, betanin, vulgaxanthin‑I, and betalain contents. The results put forth that fertilization delayed reduction in color, betanin, and betalain content of red beets during storage. Additionally, respiration rate, dry matter, and betalain content in samples can be maintained significantly during storage at 0 °C, whereas at 4 °C was effective only for pH values throughout the storage. Also, studied storage temperatures and fertilization were not effective on weight loss and vulgaxanthin‑I content. In conclusion, this research has shown the possibility of improving the desirable quality and storage-life of red beets by applying nitrogen + boron fertilization. These preliminary results could be an effective tool for predicting the quality and freshness of red beets during 3 months of storage for future studies.
... Amaranthus leafy vegetables are used as many traditional medicines, especially antimicrobial [38][39][40][41][42][43][44][45][46][47][48], anthelmintic [49][50][51][52], antiviral [53], neuroprotective [54], anti-inflammatory [55,56], antiulcer [57], anticancer [58][59][60], hepatoprotective [61][62][63][64], anti-hyperlipidemic [65][66][67][68][69][70], antidiabetic, antidepressant, antimalarial activities, and snake antidotes [71][72][73][74][75][76]. It also has abundant phytopigments, including β-cyanins, anthocyanin, β-xanthins, betalains, carotenoids, and chlorophylls [77][78][79][80][81][82][83][84] with high RSC [85][86][87][88][89][90][91][92][93][94][95]. It also has sufficient phytochemicals, including ascorbic acids, phenolic acids, and flavonoids [96][97][98][99][100][101][102] and AP [103][104][105][106][107][108][109][110][111][112][113][114][115][116][117][118][119][120]. ...
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The underutilized Amaranthus leafy vegetables are a unique basis of pigments such as β-cyanins, β-xanthins, and betalains with radical scavenging capacity (RSC). They have abundant phytonutrients and antioxidant components, such as pigments, vitamins, phenolics, and flavonoids. Eight selected genotypes (four genotypes from each species) of underutilized Amaranthus leafy vegetables were evaluated for phytonutrients, pigments, vitamins, phenolics, flavonoids, and antioxidants in a randomized complete block design under ambient field conditions with three replicates. The studied traits showed a wide range of variations across eight genotypes of two species of Amaranthus leafy vegetables. The highest fat, β-xanthins, K, dietary fiber, Mg, β-cyanins, Mn, chlorophyll ab, Zn, TP, TF, betalains, chlorophyll a content, and (RSC) (DPPH) and RSC (ABTS+) were obtained from A. tricolor accessions. Conversely, the highest protein, Cu, carbohydrates, Ca, and chlorophyll b content were obtained from A. lividus accessions. The highest dry matter, carotenoids, Fe, energy, and ash were obtained from A. tricolor and A. lividus. The accession AT2 confirmed the highest vit. C and RSC (DPPH) and RSC (ABTS+); AT5 had the highest TP content; and AT12 had the highest TF content. A. tricolor accessions had high phytochemicals across the two species, such as phytopigments, vitamins, phenolics, antioxidants, and flavonoids, with considerable nutrients and protein. Hence, A. tricolor accessions can be used as high-yielding cultivars comprising ample antioxidants. The correlation study revealed that vitamin C, pigments, flavonoids, β-carotene, and phenolics demonstrated a strong RSC, and showed a substantial contribution to the antioxidant potential (AP) of A. tricolor. The investigation exposed that the accessions displayed a plentiful origin of nutritional values, phytochemicals, and AP with good quenching ability of reactive oxygen species (ROS) that provide enormous prospects for nourishing the mineral-, antioxidant-, and vitamin-threatened community.
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In the Indian subcontinent, danta (stems) of underutilized amaranth are used as vegetables in different culinary dishes. At the edible stage of the danta, leaves are discarded as waste in the dustbin because they are overaged. For the first time, we assessed the colorant pigments, bioactive components, nutrients, and antiradical potential (AP) of the leaves of danta to valorize the by-product (leaf) for antioxidant, nutritional, and pharmacological uses. Leaves of danta were analyzed for proximate and element compositions, colorant pigments, bioactive constituents, AP (DPPH), and AP (ABTS+). Danta leaves had satisfactory moisture, protein, carbohydrates, and dietary fiber. The chosen danta leaves contained satisfactory magnesium, iron, calcium, potassium, manganese, copper, and zinc; adequate bioactive pigments, such as betacyanins, carotenoids, betalains, β-carotene, chlorophylls, and betaxanthins; and copious bioactive ascorbic acid, polyphenols, flavonoids, and AP. The correlation coefficient indicated that bioactive phytochemicals and colorant pigments of the selected danta leaves had good AP as assessed via ABTS+ and DPPH assays. The selected danta leaves had good ROS-scavenging potential that could indicate massive possibilities for promoting the health of the nutraceutical- and antioxidant-deficit public. The findings showed that danta leaves are a beautiful by-product for contributing as an alternate origin of antioxidants, nutrients, and bioactive compounds with pharmacological use.
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Fumonisin B1 (FB1) and ochratoxin A (OTA) are fungal metabolites of worldwide concern because of their effect on human and animal health, as both have been classified by IARC as possible carcinogens (Group 2B). Beetroot is a source of dietary fiber, folic acid, and vitamin C, and some studies have demonstrated their antioxidant activity. Therefore, this work presents the cytoprotective effect of beetroot extract (BRE) on a neuroblastoma cell line (SH-SY5Y cells) exposed to FB1, OTA, and its combination. Cytotoxicity was studied by the MTT ([3–4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay, for 24 h and 48h. Simultaneous treatment and pre-treatment strategies were tested with 1:512–1:2 and 1:0 dilutions of BRE, with a concentration range from 0.4 to 100 μM of FB1 and from 0.19 to 50 μM of OTA. IC50 values of 5.8 μM and 9.1 μM at 24 h and 48h, respectively were obtained for OTA while no cytotoxic effect was detected at the concentrations tested for FB1. Cytoprotection with increased viability was obtained when the simultaneous BRE + OTA strategy was performed. Finally, better protection was observed in the pretreatment strategy in which cells were exposed 24 h previously to BRE, compared to that shown in the simultaneous assay.
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Climate change causes environmental variation worldwide, which is one of the most serious threats to global food security. In addition, more than 2 billion people in the world are reported to suffer from serious malnutrition, referred to as ‘hidden hunger.’ Dependence on only a few crops could lead to the loss of genetic diversity and high fragility of crop breeding in systems adapting to global scale climate change. The exploitation of underutilized species and genetic resources, referred to as orphan crops, could be a useful approach for resolving the issue of adaptability to environmental alteration, biodiversity preservation, and improvement of nutrient quality and quantity to ensure food security. Moreover, the use of these alternative crops will help to increase the human health benefits and the income of farmers in developing countries. In this review, we highlight the potential of orphan crops, especially amaranths, for use as vegetables and health-promoting nutritional components. This review highlights promising diversified sources of amaranth germplasms, their tolerance to abiotic stresses, and their nutritional, phytochemical, and antioxidant values for vegetable purposes. Betalains (betacyanins and betaxanthins), unique antioxidant components in amaranth vegetables, are also highlighted regarding their chemodiversity across amaranth germplasms and their stability and degradation. In addition, we discuss the physiological functions, antioxidant, antilipidemic, anticancer, and antimicrobial activities, as well as the biosynthesis pathway, molecular, biochemical, genetics, and genomic mechanisms of betalains in detail.
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Background: Red pitaya peel (RPP) is a good source of polysaccharides acting as a biodegradable material, betacyanins in it possess antioxidant and pH-sensitive properties. However, RPP is commonly discarded during fruit processing. It's full of challenges to evaluate the freshness of protein-rich products rapidly and accurately. This study was aimed to develop real-time intelligent film using RPP to evaluate pork freshness. Results: Real-time intelligent films were developed with film-forming substrates (FFS) composed by 60-100% (w/w) RPP and 0-4% (v/w) glycerol in pH 4.3~8.0. Rheology tests revealed that the FFS exhibited a shear-thinning behavior. FT-IR analysis showed that molecules in the RPP interacted with glycerol and formed hydrogen bonds. It showed the film developed with FFS of 80% RPP and 2% (v/w) glycerol had strong molecular interaction, dense structure, and optimal tensile strength and elongation at break. The film with pH shifting to 7.0 had higher sensitivity to ammonia than that was prepared at original pH = 4.3, thereby this film was used to monitor freshness of pork. A visible change in the color of film was observed during the spoiling process of pork, which was correlative with the accumulated total volatile base nitrogen. Conclusion: Base on the sensitivity to ammonia and real-time evaluation of pork freshness, the film made of 80% (w/w) RPP and 2% (v/w) glycerol at pH 7.0 was recommended to be used in monitoring freshness of protein-rich food. Our findings are of great significance for ensuring meat quality and safety as well as reducing food waste. This article is protected by copyright. All rights reserved.
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Garambullo (Myrtillocactus geometrizans), endemic fruit from Mexico, contains several bioactive compounds (phenolic compounds, betalains, antioxidant fiber), highlighting it as good functional food. This research study the impact of the in vitro gastrointestinal digestion on phytochemicals bioaccessibility from garambullo and its antioxidant capacity. The fruit contained previously unidentified phytochemicals in the polar and non-polar extracts (acetone and hexane). The bioaccessibility decreased in the mouth and stomach for flavanones (up to 11.9 and 8.9 %, respectively), isoflavones (up to 20.0 and 9.2 %, respectively), flavonols (up to 15.2 and 15.7 %, respectively), hydroxycinnamic acids (up to 21.7 and 13.1 %, respectively), and betalains (up to 10.5 and 4.2 %, respectively); hydroxybenzoic acids was increased (up to 752.8 and 552.6 %, respectively), while tocopherols increased in the mouth (127.7 %) and decreased in the stomach (up to 90.3%). In the intestinal phase, the digestible fraction shows low phytochemicals bioaccessibility, and some compounds were recovered in the non-digestible fraction. Antioxidant capacity decreased in the different compartments of the gastrointestinal tract, being higher in the mouth (872.9, 883.6, 385.2, and 631.2 µmol TE/g dw by ABTS, DPPH, ORAC, and FRAP, respectively) and stomach (836.2, 942.1, 289.0, and 494.9 µmol TE/g dw ABTS, DPPH, ORAC, and FRAP, respectively). The results indicate that digestion positively or negatively affects compounds' bioaccessibility depending on their structural family, and the antioxidant capacity decreases but remains higher than other functional foods.
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Copao (Eulychnia acida Phil.) is an endemic arborescent cactus restricted mainly to the semi-arid Coquimbo Region (29°54′28″ S, 71°15′15″ W), Chile. The area of distribution is from sea level to 1200 m.a.s.l. The edible fruit called rumpa is generally round, with green or pink peel and small scales on its surface, showing wide variability in size and weight. The aim of this work was to characterize the rumpa harvested in January 2009 and 2010 in three sectors of Coquimbo Region to determine chemical and nutritional composition in three fractions: pulp with seeds, juice, and peel. The research showed that this fruit is a good natural source of mainly soluble dietary fiber, which has a jellied texture and is present in the three fractions analyzed: 2% for juice, 3% for pulp with seeds, and approximately 5% for peel, making it potentially a good source of hydrocolloids for the food industry. The fruit is also a good source of vitamin C; around 55 mg 100 g-1 in peel, and 30 mg 100 g-1 in pulp with seeds and juice, values considered high compared to 18 mg 100 g-1 for prickly pear (Opuntia ficus-indica [L.] Mill.) The main minerals were: K, Mg, Ca, and P. Total polyphenols and betalain pigments were also determined in the pulp with seeds and pink peel fractions, respectively. The nutritional characteristics, together with its high water content of around 96%, make rumpa a promising raw material for agro-industrial development of natural juices or isotonic drinks. This characterization helps in the recovery of an endemic native species by reducing potential threats to destroy wild populations of E. acid, especially near agricultural areas, and by promoting habitat conservation of the species in the region.
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Due to population growth and subsequent growing energy demand, clean energy generation is one of the major challenges today and in the future. Dye-sensitized solar cells (DSSCs) is one of the new approaches to producing clean, endless energy. In this review, the primary function, structure, performance parameters, and key elements of DSSCs are analyzed first, with a focus on the photosensitizer as the crucial part due to electron production. Photosensitizers based on natural resources recently attracted attention because of their economic and environmental advantages, but there are substantial challenges such as low conversion efficiency and long term stability. Also, diverse and, in some cases, contradictory results presented in the literature make conclusions difficult. Here, different challenges about DSSCs based on natural dyes are categorized and discussed according to the published papers, and possible solutions are presented, which could shed light on future investigations. Furthermore, according to different factors, such as average solar radiation and economic/technological aspects, DSSCs based on natural dyes are proposed to be the most promising renewable energy technology for arid to semi-arid, sunny countries like Iran in the future. Accordingly, the performance of DSSCs based on natural dyes manufactured using dye extract of different plants grow in Iranian is summarized then. In recent years, many DSSCs based on natural dyes have been manufactured using different plants grown in different parts of the country. Interestingly, it is possible to extract many natural dyes for DSSCs based on natural dyes from agricultural wastes such as saffron petals and walnut shells, of which thousand tons them are disposed every year.
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A method for the screening of antioxidant activity is reported as a decolorization assay applicable to both lipophilic and hydrophilic antioxidants, including flavonoids, hydroxycinnamates, carotenoids, and plasma antioxidants. The pre-formed radical monocation of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS*+) is generated by oxidation of ABTS with potassium persulfate and is reduced in the presence of such hydrogen-donating antioxidants. The influences of both the concentration of antioxidant and duration of reaction on the inhibition of the radical cation absorption are taken into account when determining the antioxidant activity. This assay clearly improves the original TEAC assay (the ferryl myoglobin/ABTS assay) for the determination of antioxidant activity in a number of ways. First, the chemistry involves the direct generation of the ABTS radical monocation with no involvement of an intermediary radical. Second, it is a decolorization assay; thus the radical cation is pre-formed prior to addition of antioxidant test systems, rather than the generation of the radical taking place continually in the presence of the antioxidant. Hence the results obtained with the improved system may not always be directly comparable with those obtained using the original TEAC assay. Third, it is applicable to both aqueous and lipophilic systems.
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Betalains (betacyanins and betaxanthins), the main pigments of red beet (Beta vulgaris) roots, showed an antiradical effect when measured by the destruction of the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS) free radical generated by the horse-radish peroxidase/hydrogen peroxide-mediated oxidation of ABTS. The antiradical activity of betacyanins was greater than that of the betaxanthins and increased with the pH of the reaction medium. The different antiradical properties shown by both types of betalain is discussed in light of the respective ease with which it is possible to withdraw one electron from their molecules and the stability of their corresponding radicals.