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Flavones and flavonoids are known to have potent antioxidant activity due to intracellular free radical scavenging capacities. Flavonoids are found ubiquitously in plants as a member of polyphenolic compounds which share diverse chemical structure and properties. Quercetin is among the most efficient antioxidants of the flavonoids. The antioxidant property of quercetin has been highlighted in this review. These compounds have pivotal role in treatment of diabetes, cancers and some cardiovascular diseases.
Turkish Journal of Agriculture - Food Science and Technology, 4(12): 1134-1138, 2016
Turkish Journal of Agriculture - Food Science and Technology,
Turkish Science and Technology
Antioxidant Activity of Quercetin: A Mechanistic Review
Senay Ozgen1, Ozgur Kivilcim Kilinc1, Zeliha Selamoglu2*
1Department of Plant Productions and Technologies, Faculty of Agricultural Sciences and Technologies, Omer Halisdemir University,
51240 Niğde, Turkey
2Department of Biotechnology, Faculty of Arts and Science, Omer Halisdemir University, 51240 Niğde, Turkey
Article history:
Received 09 November 2016
Accepted 29 November 2016
Available online, ISSN: 2148-127X
Flavones and flavonoids are known to have potent antioxidant activity due to intracellular
free radical scavenging capacities. Flavonoids are found ubiquitously in plants as a
member of polyphenolic compounds which share diverse chemical structure and
properties. Quercetin is among the most efficient antioxidants of the flavonoids. The
antioxidant property of quercetin has been highlighted in this review. These compounds
have pivotal role in treatment of diabetes, cancers and some cardiovascular diseases.
Oxidative stress
Türk Tarım – Gıda Bilim ve Teknoloji Dergisi, 4(12): 1134-1138, 2016
Kuersetinin Antioksidan Aktivitesi: Mekanik Bir Derleme
Geliş 09 Kasım 2016
Kabul 29 Kasım 2016
Çevrimiçi baskı, ISSN: 2148-127X
Flavonlar ve flavonoidlerin, hücre içi serbest radikal süpürme kapasitelerinden dolayı
güçlü antioksidan aktiviteye sahip oldukları bilinmektedir. Flavonoidler, polifenolik
bileşiklerin çeşitli kimyasal yapı ve özelliklerini paylaşan bir üyesi olarak bitkilerde
bulunmaktadır. Quercetin, flavonoidlerin en etkili antioksidanları arasında yer almaktadır.
Bu derlemede quercetin'in antioksidan özellikleri vurgulanmıştır. Bu bileşikler diyabet,
kanser türleri ve bazı kardiyovasküler hastalıkların tedavisinde önemli rol
Anahtar Kelimeler:
Oksidatif stres
* Sorumlu Yazar:
Ozgen et al., / Turkish Journal of Agriculture - Food Science and Technology, 4(12): 1134-1138, 2016
Flavonoids are found ubiquitously in plants as a
member of polyphenolic molecules that share diverse
chemical structure and properties. There are more than
4.000 various flavonoids have been characterized within
the main flavonoid group which involve flavonols,
flavones, flavanones, catechins, anthocyanidins,
isoflavones, dihydroflavonols and chalcones (Cook et al.,
1996). The food industry uses natural antioxidants to
protect nutrients and color in the food. Recently, the
numbers of the studies conducted for the use of
flavonoids in different areas of industry are increasing.
Similarly, possible use of these compounds is being
common due to their antioxidant properties in the area of
food, textile, leather, metallurgy, medicine and
agriculture. Thus, quercetin is a common source for food
and pharmaceutical industries. Quercetin (3, 5, 7, 3′, 4′-
pentahydroxyflavone) is classified as a flavonol which is
one of the five subclasses and major dietary flavonoids
distributed in both cultivated and wild plants. (Cook et al.,
1996; D'Andrea, 2015).
Many factors, for instance, development of
technologies, the greenhouse effect, environmental
pollution, smoking, radiation and many chemicals, cause
negative effects of oxidative stress in the human body, as
a result, stress-free radicals occur. It is proven that
oxidative stress and free radicals provoke aging and
disease in the body. Characterization of components
capable of natural flavonoid antioxidants and their
antioxidative effects have become increasing interest
(Selamoglu et al., 2016). Antioxidants are organic
compounds with non enzymatic low concentrations that
prohibit the free radical oxidation mechanism (Das,
1989). Flavones and flavonoids, particularly quercetin,
are known to reveal important cytotoxicity process
against cultured human cells via raising intracellular
reactive oxygen species amount (Yáñez et al., 2004). In
this review, the effect of quercetin for the role of free
radical scavenger will be presented.
Chemistry of Quercetin
A hydroxyl group in third carbon, a double bond
between second and third carbon, a carbonyl group in
fourth carbon and polyhydroxylated A and B aromatic
rings (Figure 1) have main role in antioxidant proprieties
of these compounds (Cook et al., 1996).
The first resonant structure where B ring has an ortho-
catechol group may enable the forming of intra- and inter-
molecular hydrogen bonds. Indeed, the flavones, include
an ortho-catechol group (myricetin, quercetin, and
luteolin) are more acidic than apigenin and kaempferol, in
which the B-ring only have a 4′ hydroxyl group. Luteolin
and quercetin have two hydroxyl groups in the B-ring, on
the contrary of myricetin. Thus, the more numbers of
connected hydroxyl groups in the B-ring defines the
acidity capacity.
The scavenging mechanism of the free radical by
quercetin has been discussed on the rational of different
AM1 and quantum mechanics calculation, the attained
boundary orbitals and total spin intensity (Vasilescu and
Girma, 2002). The analysis results of the spin density near
by the attained free radical 4′-quercetin implies that the
essential intensity of spin α(↑) is condensed in the B ring
on the O4′ oxygen. They noticed also a light
delocalization of spins α(↑) and β(↓) on the B ring and on
a part of the C ring. Authors concluded that quercetin
antioxidant capacity may be related to basically with the
B ring and a half of the C ring (Vasilescu and Girma,
The correlation of these flavonoids with Cu2+ ions was
examined for their obscure composition of chelation or
modification through oxidation, as well as in their
structural relation (Brown et al., 1998). It has been
implied that the ortho 3', 4'-dihydroxy substitution in the
B ring is critical for a Cu2+-chelate formation which
affects the antioxidant activity. Furthermore, it has been
shown that the existence of a 3-hydroxy group in the
flavonoid structure promotes the oxidation of quercetin
and kaempferol. On the other hand, luteolin and rutin are
absent in the 3-hydroxy group which they do not oxidize
as easily in the existence of Cu2+ ions (Brown et al.,
1998). In addition, it is observed that complexation of
magnesium (Mg+2) cation increases the free radical
scavenging capacity of quercetin which inhibits oxidant
damage and cell mortality via different pathways (Ghosh
et al., 2015).
Figure 1 The structure of quercetin (Modified from
Mitchell, 1965).
Sources of Quercetin
Quercetin is one of natural flavonoid group that is
most common as a secondary metabolite in plants.
Production of synthetic flavonoids has not been practiced
yet. Hence, plants are the only sources for quercetin
(Abdelmoaty et al., 2010). Major vegetables and fruits
that are commonly consumed comprise different classes
of flavonoids in varied amount. It has been found that
onion has the highest amount of quercetin (about 300
mg/kg) among tested nutrition (Beecher, 1999). Other
vegetables, such as broccoli and kale, included quercetin
Ozgen et al., / Turkish Journal of Agriculture - Food Science and Technology, 4(12): 1134-1138, 2016
and kaempferol, but at much lower content. However, tea
contains a high amount of catechins but low amounts of
flavonoid quercetin (Beecher, 1999). The colour of fruits
and vegetables indicates amount of flavonoids, as red
grapes, cherries and blueberries have a significant amount
of variant anthocyanins. Most of these fruits also contain
flavonoids, especially quercetin (Beecher, 1999).
Quercetin and Oxidative Stress
The antioxidant character of quercetin is associated to
chemical structure, especially the presence and location of
the hydroxyl (OH) substitutions and the catechol-type B-
ring (Rice-Evans et al., 1996; Wang et al., 2006). The
structural properties of a potent antioxidant capacity is
due to the presence of (i) an ortho-dihydroxy or catechol
group in the B-ring, (ii) a 2,3-double bond, and (iii)
hydroxyl substitution at positions 3 and 5 (Bors et al.,
1990). Growing evidence has demonstrated that quercetin,
which is featured by a hydroxylation form of 3, 5, 7, 30,
and 40 and a catechol B-ring, contains all the structural
properties of an antioxidant agent (Silva et al., 2002;
Rietjens et al., 2005). Quercetin has anticarcinogenic and
anti-inflammatory properties with antioxidant and free
radical scavenging effects. However, quercetin may also
be diverted into reactive molecules (Metodiewa et al.,
1999; Boots et al., 2003). In vitro, the oxidative
degradation of quercetin has been showed to result in the
formation of a free radical orthosemiquinone
intermediate, which may afterward be changed to the
parent molecule or to an orthoquinone, nearby the
manufacturing of reactive oxygen species (Metodiewa et
al., 1999; Boots et al., 2003). In conclusion, the possible
pro-oxidant property of quercetin, especially at high dose
levels, must be emphasized (Rietjens et al., 2005). As a
result, the prooxidant effect may be accountable for the in
vitro mutagenic action of quercetin. Also, the researchers
reported that under aerobic conditions, quercetin was
demonstrated to produce dose-dependent DNA damage
and lipid peroxidation in isolated rat liver nuclei and
oxygen radicals produced by autooxidation of the
flavonol (Rahman et al., 1992; Sahu and Washington,
1991). Oxidative stress is related to reactive oxygen
species which is the main factor for viral hepatitis,
fibrosis, cirrhosis and liver cancer formation (Preedy et
al., 2014). Recent studies show that some flavonoids
prevent the occurrence of superoxide and hydroxyl
radicals which cause lipid peroxidation.
Some researchers suggested that quercetin has
antimicrobial, antiviral, antioxidative and anti-
inflammatory activities (Doğan et al., 2015; Gutteridge,
1995). Also, it is able to increase the cellular antioxidant
potential via the Nrf2 pathway (Gutteridge, 1995).
Another study by Doğan et al. (2015) has showed that
quercetin is able to prevent against the toxic action of
chemotherapeutic substances treated prior to pregnancy
(Doğan et al., 2015). Quercetin was applied at a dose of
10 mg/kg/day by oral gavage. After 48 h of the
experimental chemotherapy exposure, female rats were
transferred to cages including male rat for mating.
According to this study, women who have been exposed
to chemotherapy and may be pregnant should be treated
with antioxidant molecules, such as quercetin to decrease
the risk of injury to fetal brain tissues. In addition, the
data of this investigation assessed the hypothesis that
quercetin can prevent the toxic actions of
chemotherapeutic compounds treated prior to pregnancy
(Doğan et al., 2015).
Some experimental studies on animals are declared
that the antioxidant effects of quercetin decrease oxidative
injury to the tissues such as the brain, heart in ischemic
reperfusion damage and exposure to agents that induce
oxidative stress (Doğan et al., 2015; Bayne and Sohal,
2002). It is well established that natural antioxidants are
usually harmless to human body. They are molecules that
prevent early aging via blocking the catasthropic effects
of the free radicals, many diseases and chain reactions
(Elik et al., 2007).
Antioxidant enzyme activities are substantially
enhanced by quercetin treatment (Elik et al., 2007). The
study of Elik et al. (2007) proved that quercetin as a
flavonoid with antioxidant characteristics demonstrates
antidiabetic effects (Elik et al., 2007). This compound
also has protection against oxidant damage to the heart,
brain, liver, aorta and kidney for mid-term or long-term
diabetic rat (Elik et al., 2007). Thus, quercetin increases
the antioxidant defence capacity.
It has been shown that flavonoids could inhibit
enzymes like cyclooxygenases and protein kinases where
they are part of cell proliferation and apoptosis processes
(Abdelmoaty et al., 2010). In addition, doses of 1550
mg/kg body mass quercetin was able to of normalize
blood glucose level, augmenting liver glycogen
ingredients and dramatically decreasing serum cholesterol
and low density lipoprotein (LDL) levels in alloxan
diabetic rats (Abdelmoaty et al., 2010). Furthermore,
treatment of quercetin to isolated rat islets increased
insulin production by 4470% with changing in calcium
flows and in cyclic nucleotide metabolism (Abdelmoaty
et al., 2010).
Consumption of flavonoids showed a reduction in
coronary heart disease (Hertog et al., 1994). The study
conducted in Japan showed that there was a decreased on
both total and LDL-cholesterol concentration when
plasma quercetin is increased (Hertog et al., 1994). In
another study in Finland showed that diet rich in apple
and onion increased quercetin level which was helpful to
reduce coronary mortality (Knekt et al., 1996).
Each alive organism is able to prevent negative effects
of free radicals with antioxidative protection system.
However, this system is not strong enough to prevent an
increase in the amount of radical. Consequently, oxidative
stress (cell damage) occurs in this situation. Low level of
stress induces a cell to activate extra defence system,
although, high-stress level causes the death of cells which
damages organisms (Çıkrıkçı, 2005). All these studies are
demonstrating that quercetin has an anti-oxidative effect
to inhibit oxidative stress.
A series of epidemiological studies proved that a lack
of association between flavonoids consumption up to 68
Ozgen et al., / Turkish Journal of Agriculture - Food Science and Technology, 4(12): 1134-1138, 2016
mg total flavonoids/day (in large portion by high
quercetin level) and incidence of all variety of cancer
(Hertog et al., 1995; Lin et al., 2006). On the other hand,
there are studies indicated a negative correlation between
up to 40 mg/day flavonoid consumption (95% of it
quercetin) and cancer incidence (Knekt et al., 1997; Knekt
et al., 2002).
It is demonstrated that triptolide (TP)-induced
oxidative stress and a decrease of testosterone generation
could be prevented by quercetin (Hu et al., 2015).
Different concentrations of TP were applied to Leydig
cells to cause oxidative stress with high intracellular
reactive oxygen species resulted in reduction activities
and expressions of glutathione peroxidase and superoxide
dismutase. Results of this study imply that quercetin
could lower the TP-induced reproductive toxicity, which
support the usage of TP.
The inhibition effect of quercetin against oxidative
stress, which caused by sodium fluoride, was investigated
in rat’s liver (Nabavi et al., 2012). Five groups of rats
were treated with different diets; the first group served
standard diet, the second group was intoxicated with
sodium fluoride (600 ppm) via drinking water for a week.
The third, fourth and fifth groups were applied with
quercetin at a dose of 10 and 20 mg/kg and vitamin C (as
the positive control) at a dose of 10 mg/kg
intraperitoneally for 1week ahead of sodium fluoride
intoxication, seriatim. Activities of superoxide dismutase
and catalase, the amount of decreased glutathione and
lipid peroxidation end product were measured 1 week
later treatments of rat liver. According to the data of this
work that quercetin preserves rat liver from sodium
fluoride activated oxidative stress, most likely by its
antioxidant action (Nabavi et al, 2012). It is also
demonstrated that quercetin prevents perfluorooctanoic
acid-induced liver damage via mitigating oxidative stress
and inflammatory response in mice (Zou et al., 2015). As
pointed out, mitochondrial oxidative stress has a main
role in the pathology of myocardial infarction (Czepas
and Gwoździński, 2014). In this study, pretreatment of
quercetin reduced the activities of serum creatine kinase,
lactate dehydrogenase, heart mitochondrial lipid
peroxidation products and dramatically enhanced the
amounts of mitochondrial antioxidants. In addition,
quercetin also cured the activities of tricarboxylic acid
cycle and respiratory chain enzymes almost normal level
in myocardial infarcted rats. The action of quercetin on
cardiac mitochondrial oxidative stress could reduce
mitochondrial lipid peroxidation; enhance levels of
mitochondrial antioxidants and activities of mitochondrial
marker enzymes. As a result, heart mitochondria of rat are
protected to isoproterenol-stimulated oxidative stress in
vivo in myocardial infarction (Czepas and Gwoździński,
Quercetin is the most abundant polyphenolic in human
food and the absences of its toxicity-genotoxicity has
been proved. It has high importance due to chemo
preventive and anticancer values. In general, all these
values might point out the possible treatment of quercetin
as cardio protectant through anthracycline chemotherapy.
Moreover, all these favourable impacts to anthracycline-
induced complications of chemotherapy need to be more
studied and validated both in animal and clinical works.
The experiment was established to test the
hepatoprotective effect of quercetin compared to N-
acetylcysteine (NAC) against hepatic I/R injury in rats
and to determine iNOS, eNOS, and NOSTRIN protein
expressions, as a possible mechanism of its
hepatoprotective effect. As a result, quercetin application
improved eNOS protein expression with a simultaneous
decline in iNOS and NOSTRIN protein expressions. In
addition, pretreatment of quercetin decreased serum
aspartate aminotransferase, alanine aminotransferases and
hepatic myeloperoxidase activities and recover the extinct
content of decreased glutathione, malondialdehyde, and
nitric oxide levels (Abd-Elbaset et al., 2015).
Neurodegenerative disorders are formed with complex
processes, basically associated to advance brain injury
capturing cellular death. Biochemical reactivity related to
these processes in Alzheimer’s disease contains, among
others, metal-induced oxidative stress promoting to
neuronal cell demise. One of the active redox metals
causing oxidative stress is Cu (II) (Naday et al., 2015).
Lately, the effort is to produce bioactive hybrid
nanoparticles that have the capability to work as host-
carriers for potential antioxidants, for instance, the natural
flavonoid quercetin. In molecular technology silica
nanoparticles were assembled with synthetic protocols to
produce PEGylated and CTAB-modified materials.
Conclusion and Future Prospects
The current review deals with the basic biological
functions of quercetin, such as antioxidant, anti-
carcinogenic, anti-inflammatory, and cardio protective
properties. Furthermore, prevention of tumour
development and possibility of flavonoid-drug interaction
have been also discussed. We shared these biological
properties of quercetin with a common mechanism of
antioxidant action in this review. Critical evaluation of
biological effects of quercetin leads to raising a
conclusion that at estimated dietary intake levels would
not cause adverse health problems, even; daily
consumption would be extremely beneficial for human
daily activities.
Competing Interest
The authors declare that they have no conflict of
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... In preclinical studies, many natural products have recently been reported to alleviate kidney disease by modulating oxidative stress and inflammation (11). As a natural product, polyphenols are widely distributed in most plants and classified as phenolic acids, flavonoids, stilbenes, and lignans according to their structural properties (12).Nuclear factor E2-related factor 2 (Nrf2) is a significant regulator of antioxidant enzymes that protect the body from oxidative stress and inflammation, and Nrf2/antioxidant response element (ARE) signaling has been suggested as a promising target against oxidative stress-mediated diseases, such as diabetes and fibrosis. Dietary polyphenols, such as resveratrol, curcumin, and quercetin, can modulate Nrf2 signaling by mediating various kinases upstream of Nrf2 and also directly activate the expression of Nrf2 as well as downstream targets, such as heme oxygenase 1(HO-1) superoxide dismutase(SOD), and catalase (CAT), to inhibit oxidative stress and regulate inflammatory mediators (13-15). ...
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Diabetic nephropathy (DN) often leads to end-stage renal disease. Oxidative stress demonstrates a crucial act in the onset and progression of DN, which triggers various pathological processes while promoting the activation of inflammation and forming a vicious oxidative stress-inflammation cycle that induces podocyte injury, extracellular matrix accumulation, glomerulosclerosis, epithelial-mesenchymal transition, renal tubular atrophy, and proteinuria. Conventional treatments for DN have limited efficacy. Polyphenols, as antioxidants, are widely used in DN with multiple targets and fewer adverse effects. This review reveals the oxidative stress and oxidative stress-associated inflammation in DN that led to pathological damage to renal cells, including podocytes, endothelial cells, mesangial cells, and renal tubular epithelial cells. It demonstrates the potent antioxidant and anti-inflammatory properties by targeting Nrf2, SIRT1, HMGB1, NF-κB, and NLRP3 of polyphenols, including quercetin, resveratrol, curcumin, and phenolic acid. However, there remains a long way to a comprehensive understanding of molecular mechanisms and applications for the clinical therapy of polyphenols.
The emergence of methicillin-resistant Staphylococcus aureus (MRSA) led to the failure of conventional antibiotic treatment, resulting in serious morbidity and mortality. The biofilm formation of S. aureus is a potential mechanism for drug resistance. SarA is an important regulatory protein for the formation of S. aureus biofilm. In this study, the global regulator SarA was used as a target to virtually screen natural active monomers. SarA inhibitor quercetin (QEN) was assessed. Molecular docking and kinetic simulation showed that QEN was stably bound to the formation site of SarA dimer. Spectral analysis verified that QEN was bound to SarA and changed its conformation. In vitro biofilm, the culture showed that 4 µg/mL QEN significantly inhibited biofilm formation, and the production of extracellular polymers and eDNA concentration significantly reduced. Scanning electron microscopy and laser confocal microscopy further confirmed the inhibitory effect of QEN on biofilm formation. At the same time, a decrease in the transcription level of sarA and its downstream genes related to biofilm regulation and a decrease in the expression level of SarA were also observed, confirming the QEN-induced inhibition of sarA . In conclusion, the results of this study revealed SarA-mediated anti-biofilm effect of QEN on MRSA. IMPORTANCE Anti-biofilm is an important strategy against Staphylococcus aureus chronic infection. SarA is a positive regulator of biofilm formation in S. aureus . In this study, we identified the SarA inhibitor quercetin using computer simulation screening. Previous studies have shown that quercetin inhibits biofilm; however, the underlying mechanism remains unknown. This study revealed the inhibitory effect of quercetin on the SarA protein. We also isolated the SarA protein and confirmed its interaction with quercetin in vitro . Besides, the inhibitory effect of quercetin on the transcription and translation levels of the SarA protein was also determined. The effects of quercetin on S. aureus biofilm inhibition and biofilm components were consistent with the changes in the transcription level of biofilm-related genes regulated by SarA. In summary, our study revealed the mechanism by which quercetin affects biofilm formation by inhibiting the transcriptional regulator SarA of S. aureus .
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Quercetin is the major polyphenolic flavonoid that belongs to the class called flavanols. It is found in many foods, such as green tea, cranberry, apple, onions, asparagus, radish leaves, buckwheat, blueberry, broccoli, and coriander. It occurs in many different forms, but the most abundant quercetin derivatives are glycosides and ethers, namely, Quercetin 3-O-glycoside, Quercetin 3-sulfate, Quercetin 3-glucuronide, and Quercetin 3′-metylether. Quercetin has antioxidant, anti-inflammatory, cardioprotective, antiviral, and antibacterial effects. It is found to be beneficial against cardiovascular diseases, cancer, diabetes, neuro-degenerative diseases, allergy asthma, peptic ulcers, osteoporosis, arthritis, and eye disorders. In pre-clinical and clinical investigations, its impacts on various signaling pathways and molecular targets have demonstrated favorable benefits for the activities mentioned above, and some global clinical trials have been conducted to validate its therapeutic profile. It is also utilized as a nutraceutical due to its pharmacological properties. Although quercetin has several pharmacological benefits, its clinical use is restricted due to its poor water solubility, substantial first-pass metabolism, and consequent low bioavailability. To circumvent this limited bioavailability, a quercetin-based nanoformulation has been considered in recent times as it manifests increased quercetin uptake by the epithelial system and enhances the delivery of quercetin to the target site. This review mainly focuses on pharmacological action, clinical trials, patents, marketed products, and approaches to improving the bioavailability of quercetin with the use of a nanoformulation.
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Purpose To evaluate the modulatory properties of Calendula officinalis L. (Asteraceae) (C. officinalis) extract on cafeteria diet-fed rats. Methods A cafeteria diet was administered ad libitum for 45 days to induce dyslipidemia. Then, the rats were treated with the formulations containing C. officinalis in the doses of 50, 100, and 150 mg/kg or only with the vehicle formulation; the control group received a commercial ration. Results The cafeteria diet decreased glutathione S-transferase activity and high-density lipoprotein plasmatic levels and damaged the hepatic architecture. The C. officinalis extract was able to reduce lipid infiltration in liver tissue and to modulate oxidative stress and lipid profile markers. Conclusions The correlations between the variables suggest a pathological connection between oxidative stress markers and serum lipid profile. Key words Calendula; Dyslipidemias; Flavonoids; Oxidative Stress; Lipids
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Quercetin is a bioactive natural compound with an antioxidative property that can potentially modify plant physiology. The current investigation aimed to gauge the effect of different concentrations of foliar spray of quercetin (0, 0.5, 1, 1.5, 2.0 mM) on several morphological and physio-biochemical performances of Abelmoschus esculentus L. (Moench.) plants under normal environmental conditions. The foliar spray on the plant leaves was applied 25 days after sowing (DAS) and continued up to 30 DAS once each day. The plants were sampled at 30 and 45 DAS to monitor several parameters. The foliar treatments of quercetin significantly upgraded all the studied parameters. The results direct that most of the traits such as growth, nutrient uptake, photosynthetic, and enzyme activities were promoted in a dose-dependent way. Quercetin application lowered the reactive oxygen species (ROS) buildup by increasing the antioxidant enzyme activities. Microscopic investigations further revealed a significant enhancement in the stomatal aperture under quercetin application. Out of several doses tested, 1 mM of quercetin proved best and can be used for further investigations.
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Portuguese wine industry by-products are often undervalued but constitute a potential source of bioactive phenolic compounds that can be applied as a natural additive in several industries. In this context, the present study aimed to evaluate the nutritional composition, and the phenolic profile of two Portuguese Vitis vinifera L. grape pomaces (Touriga Nacional (red variety) and Alvarinho (white variety), and to correlate their chemical characterizations with their antioxidant activities. Strong correlations were observed between the presence of phenolic compounds and antioxidant activities, which enhances the application of pomace extracts in food and pharmaceutical areas. The high content of total phenolic compounds (25 - 41 g/ kg dry extract) and of flavonoids (9.2 - 18 g/ kg dry extract) found in both samples make these pomaces excellent candidates as food additives in food products, as well as antioxidant agents, such as natural dyes. Some polyphenols were identified by High Performance Liquid Chromatography (HPLC), being rutin and catequin the highest compounds found in red grape pomace (Touriga Nacional) while quercetin was only quantified in white grape pomace (Alvarinho). Cis-resveratrol was quantified in both grape pomace, which opens horizons for its use since this compound has considerable chemopreventive effects in the three main gains of carcinogenesis. As expected, the anthocyanin content was significantly higher in red grape pomace (37 g/ kg dry extract), emphasizing its interest as a natural food additive. Based on the findings, it is possible to conclude that these by-products have additional value, making them potentially useful in the food, pharmaceutical, and cosmetic industries.
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Available synthetic antioxidants have been reported to have mutagenic and toxic effects. On the other hand, natural antioxidants show their superiority as they are not or less toxic. Passiflora foetida has the potential as an antioxidant, but the investigation of the antioxidant activity of the P. foetida chromatography column fraction has not been reported. This studied aims to investigate the antioxidant activity of the column chromatographic fractions of P. foetida leaves. An antioxidant assay using the DPPH and FRAP methods. The extraction was carried out by graded maceration, then fractionation using column chromatography. The antioxidant activity test was carried out using the DPPH and FRAP methods. Thin Layer Chromatography analysis was performed to determine the chromatogram pattern. The EC50 using DPPH method from n-hexane extract: 129.035 µg/mL, ethyl acetate extract: 206.398 µg/mL, methanol extract: 97.453 µg/mL, while the EC50 using FRAP method from n-hexane extract: 67.851 µg/mL, ethyl acetate extract : 68.981 µg/mL, and methanol extract: 58.787 µg/mL. Column chromatography fractions have antioxidant activity, with FMetPF6 as the fraction with the best activity, with percent inhibition 41.85±1.96 at concentration 25 µg/mL (DPPH), and with percent antioxidant activity 26.03±0.84 at concentration 9 µg/mL (FRAP). Passiflora foetida leaves have great potential as an antioxidant; both the extract and its fractions have antioxidant activity. The FMetPF6 has the best activity compare to other extracts and fractions. Further analysis to determine the various compounds in FMetPF6 using LC-MS/MS will facilitate the active compound's isolation.
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Introduction: A perennial, aromatic, tuberose plant Zingiber roseum (Roscoe.) (Zingiberaceae), flourishes in tropical and subtropical climates. In Traditional Chinese Medicine, several pharmacological properties of Zingiber roseum have been reported its antiseptic, antivertigo, and antidiarrheal activities. Therefore, the present article aims to provide insights into the ethnomedicinal, phytochemistry, and pharmacology of Zingiber roseum. Methods: The literature was compelled after systematically searching scientific databases, including Scopus, PubMed, Google Scholar, and Research Gate. The selection criteria for the plant comprised the therapeutic potential of Zingiber roseum and its active components. Moreover, to explore anti-diabetic activity, ligands of interest from Z. roseum were evaluated for their affinity towards PPAR-and PPAR-. Results and discussions: Out of 200 articles, 140 were selected for the current study, and from the para-topic literature , it was found that Zingiber roseum has numerous pharmacological properties due to the presence of phyto-constituents like flavonoids, alkaloids, phenolic chemicals, terpenoids, saponins, and phytosterols. Furthermore, in silico studies were carried out using PyRx. It was found that rosmarinic acid (-8.3 kcal/mol) and stigmasterol (-11.12 kcal/mol) exhibited the highest binding affinities for PPAR-and PPAR-, respectively, when compared to standard Rosiglitazone. Conclusion: It may be concluded that Z. roseum has several therapeutic activities. Moreover, in silico studies revealed the anti-diabetic action of Z. roseum via modulation of PPAR-and PPAR- .
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Plants are essential for human since from the beginning. Plants and their extracts are mainly used medicinal purposes both for the prevention and treatment of human diseases in many countries. Recently, studies are conducted to demonstrate the importance of natural antioxidants in human health. The purpose of these studies is 1) to identify the important plants and extract form them 2) to demonstrate the effect of these extract on human and environmental health [1]. Synthetic products are produced to meet the needs of increasing world population for food and medicine. However, serious health and environmental problems are increased by using these synthetic products. One of the most important problems in the world is to provide enough safe food for people. Antioxidant addition is necessary in order to preserve the flavor, color and vitamin content of the food. Some of these sources are containing natural antioxidants (such as spices), however, industries are extensively added synthetic antioxidants to the processed foods. Butylated hydroxy anisole and butylated hydroxy toluene, tertiary butyl hydroquinone, gallates, nordihi-droguareyetik acid are examples of synthetic antioxidants. Nowadays, especially in developed countries, public awareness shifted to human-environmental health and natural product resulted to safe food production and alternative to synthetic antioxidant products [2]. Level of health displays economic development of the society. The cheapest way to resolve this problem is that conducting research on plants that have high antioxidant compound. Consumers should be informed about the research results on chronic diseases and encouraged to consume foods that have high antioxidant properties. Antioxidant effect of plants in oxidative stress Most Agents that are used in cosmetic, food, chemical and pharmaceutical industries are obtained from medicinal and aromatic plants. Since the smell of these plants is all natural they are extremely valuable raw materials. When consumption of natural products increased consumption of plants with medicinal properties increased accordingly. Previously, these plants were collected form nature; however, with increasing demand for these plants is rapidly directed cultivation of such plants. The compounds called flavonoids and phenolic that are accumulated the most in leaves, flowers and woody portion of plants are capable to avoid oxidation of lipids, carbohydrates and proteins by giving away hydrogen on their hydroxyl group in their aromatic ring. Consequently, the use of ecological and natural products that inhibit oxidation of biomolecules in living organism became more preferable in human diet [3,4]. Antioxidants are able to retard or inhibit oxidative degradation of the compound. These compounds are effective to beginning of otooxidative and otooxdative process to prevent formation of undesirable products to form [3]. Antioxidant effect of aromatic plants in oxidative stress Reactive oxygen species are produced metabolic and physiological processes where these biomolecules have highly damaging effects. Organisms may cause harmful oxidative reactions during vital activities and the removal of these oxidative products is accomplished through enzymatic and non-enzymatic antioxidant mechanisms. An increase in oxygen production and decrease
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The pathogenesis of hepatic ischemia/reperfusion (I/R) is mediated through the generation of oxidative and nitrosative stress-induced cell injury. Hence, the present study was designed to evaluate the hepatoprotective effect of quercetin (QR) compared to N-acetylcysteine (NAC) against hepatic I/R injury in rats and to assess iNOS, eNOS and NOSTRIN protein expressions, as a possible mechanism of its hepatoprotective effect. Hepatic ischemia was surgically performed by occlusion of hepatic pedicle (hepatic artery, portal vein, bile duct) that supplies the left and medial lobes (approximately 70% of the total liver mass), for 30 minutes with a vascular clamp followed by releasing the clamp and the liver was reperfused for 30 minutes. QR-pretreatment increased eNOS protein expression with simultaneous decrease in iNOS and NOSTRIN protein expressions. It also decreased serum aspartate aminotransferase (AST), alanine aminotransferases (ALT) and hepatic myeloperoxidase (MPO) activities. In addition, it restored the depleted content of reduced glutathione (GSH) and decreased malondialdehyde (MDA) and nitric oxide (NO) levels. A notable finding is that QR alleviated I/R-induced histopathological changes. The present study illustrates the hepatoprotective effect of quercetin compared to N-acetylcysteine against ischemia/reperfusion-induced liver injury by inhibiting oxidative stress and by modulating iNOS, eNOS and NOSTRIN protein expressions.
Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death in the world. Reactive oxygen species (ROS)-induced oxidative stress has been considered a key player in the development and progression of various liver diseases, including viral hepatitis, fibrosis, cirrhosis, and liver cancer (e.g., HCC). In addition to endogenous antioxidants, quercetin available in food is the natural antioxidant to protect humans against oxidative stress. This protective effect is mediated through reducing ROS production, increasing the capacity of DNA repair, and promoting antioxidative responses in cells. In addition, several studies have found that quercetin also has an antiproliferation effect on HCC cells. Moreover, combination treatment with quercetin and chemotherapeutic drug doxorubicin induced a synergistic cytotoxic effect in HCC cells. These results together suggest that quercetin not only has an antioxidative effect to prevent oxidative stress but also has a potential anticancer effect for HCC treatment.
Great interest is currently centered on the biologic activities of quercetin a polyphenol belonging to the class of flavonoids, natural products well known for their beneficial effects on health, long before their biochemical characterization. In particular, quercetin is categorized as a flavonol, one of the five subclasses of flavonoid compounds. Although flavonoids occur as either glycosides (with attached glycosyl groups) or as aglycones, most altogether of the dietary intake concerning quercetin is in the glycoside form. Following chewing, digestion, and absorption sugar moieties can be released from quercetin glycosides. Several organs contribute to quercetin metabolism, including the small intestine, the kidneys, the large intestine, and the liver, giving rise to glucuronidated, methylated, and sulfated forms of quercetin; moreover, free quercetin (such as aglycone) is also found in plasma. Quercetin is now largely utilized as a nutritional supplement and as a phytochemical remedy for a variety of diseases like diabetes/obesity and circulatory dysfunction, including inflammation as well as mood disorders. Owing to its basic chemical structure the most obvious feature of quercetin is its strong antioxidant activity which potentially enables it to quench free radicals from forming resonance-stabilized phenoxyl radicals. In this review the molecular, cellular, and functional bases of therapy will be emphasized taking strictly into account data appearing in the peer-reviewed literature and summarizing the main therapeutic applications of quercetin; furthermore, the drug metabolism and the main drug interaction as well as the potential toxicity will be also spotlighted.
Triptolide (TP) is a diterpene triepoxide with variety biological activities, such as anti-inflammatory, anti-cancerogenic, immunomodulatory and pro-apoptotic activities. However, its clinical application was limited by potential toxicity. Quercetin (Que) is a member of flavonoids with anti-oxidant effects. In this study, we aimed to demonstrate the protective effect of Que in TP-induced oxidative stress and decrease of testosterone generation in reproductive damage. Leydig cells were treated with TP (20, 40 and 60 nM), which caused obvious oxidative stress increasing intracellular ROS, decreasing activities and expressions of GPx and SOD. Apoptosis was resulted from depolarization of mitochondrial membrane potential (ΔΨm) and release of cytochrome C (Cyt-C) showing increase of BAX/Bcl-2 ratio, caspase-3 and caspase-9. Treatment of Que (5 μM) prior to triptolide could restore all the TP-induced alteration in a certain dose range indicating that the oxidative stress might be one reason of TP-induced reproductive toxic effect. These results suggest that the compatibility with Que might reduce the TP-induced reproductive toxicity, which provide a probability to extend the usage of TP. Copyright © 2015. Published by Elsevier Ireland Ltd.
Quercetin (3,3',4',5,7-pentahydroxyflavone) one of the most abundant dietary flavonoids, has been investigated in the presence of magnesium (II) in methanol. The complex formation between quercetin and magnesium (II) was examined under UV-visible, Infra-red and (1)H NMR spectroscopic techniques. The spectroscopic data denoted that quercetin can reacts with magnesium cation (Mg(+2)) through the chelation site in the quercetin molecule. The free radical antioxidant activity of the complex with respect to the parent molecule was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. It was observed that the free radical scavenging activity of quercetin was increased after complexation of magnesium (Mg(+2)) cation. Copyright © 2015 Elsevier B.V. All rights reserved.
The aim of the present study was to investigate the protective effect of quercetin (Que) against perfluorooctanoic acid (PFOA)-induced liver injury in mice and its possible mechanisms of action. Mice were intragastrically administered PFOA (10mg/kg/day) alone or in combination with Que (75mg/kg/day) for 14 consecutive days. The hepatic injury was evaluated by measuring morphological changes, liver function, oxidative stress, inflammatory response and hepatocellular apoptosis. Compared with mice treated with PFOA alone, simultaneous supplementation of Que significantly decreased serum levels of liver injury indicators alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase and total bile acids. Moreover, Que treatment inhibited the production of oxidative stress biomarkers malondialdehyde, hydrogen peroxide and 8-hydroxy-2'-deoxyguanosine, reduced the levels of proinflammatory cytokines interleukin 6, cyclooxygenase-2 and C-reactive protein, and decreased the number of TUNEL-positive cells in the liver of PFOA-treated mice. These results combined with liver histopathology demonstrated that Que exhibited a potential protective effect against PFOA-induced liver damage via mechanisms involving the attenuation of oxidative stress, alleviation of inflammation and inhibition of hepatocellular apoptosis. Copyright © 2015. Published by Elsevier B.V.