Original articleBioactive effects of quercetin in the central nervous system: Focusing on the mechanisms of actions
Introduction
Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is an unique bi-flavonoid that was first isolated by the physiologist Albert Szent-Györgyi de Nagyrápolt, a Nobel Prize winner for Physiology/Medicine in the year 1936 [1]. The name “quercetin” is derived from the latin name “quercetum” meaning “oak forest, quercus oak”. Vernacular names of quercetin are quercetine, sophretin, memetin [2]. Quercetin is a major component of flavonol subclass and represents 60–75% of total flavonoid intake. It is primarily conjugated with a carbohydrate moiety and forms the backbone of other flavonoids such as rutin, hesperidin, naringenin and tangeritin [3]. Medicinal herbs widely used in traditional ayurvedic, unani, Chinese medicine and Native American remedies contains rich source of quercetin. Multiple pharmacological applications of quercetin, including antioxidant, neuroprotective, anti-viral, anti-cancer, cardiovascular, anti-microbial, anti-inflammatory, hepatoprotective and anti-obesity activities, have made this phytochemical a promising food component for the prevention of lifestyle related disorders [4].
Section snippets
Sources of quercetin
Quercetin is commonly distributed in vegetables, fruits, nuts and grains in association with sugars, phenolic acids and alcohols (Table 1). It is widely distributed in the plant kingdom, specifically in rinds and barks and it is responsible for the bright color of fruits and vegetables. High concentration of quercetin is found in vegetables such as onions (Allium cepa L.), asparagus (Asparagus officinalis L.), and red leaf lettuce (Lactuca sativa L.), while lower concentration has been reported
Chemistry and bioavailability of quercetin
Quercetin is 2-(3,4-dihydroxyphenyl)-trihydroxy-4Hchromen-4-one with molecular weight 302.24, melting point 316 °C, molecular formula C15H10O7. Quercetin consists of five hydroxyl groups whose presence determines the compound’s biological activity and the possible number of derivatives. Quercetin is generally synthesized either according to the Kostanecki’s method or Robinson method. The Kostanecki method involves claisen condensation of 1 2,4-dimethoxy-6-hydroxyacetophenone with
Protective effects on cardiovascular disease
Quercetin protects against coronary heart disease (CHD) by preventing oxidation of LDL (bad) cholesterol. Regular intake of diet rich in quercetin prevents CHD in elderly persons. Scientific evidences illustrated that quercetin exhibited protective effect against cardiovascular diseases such as atherosclerosis, ischemia-reperfusion injury, cardiotoxicity and hypertension [5], [23]. Anti-inflammatory effect of quercetin plays a key role in reducing cardiovascular endangering factors such as
Neuroprotective effect of quercetin: an overview
Brain disorders are considered as the most serious health problems of the modern society. More than 600 disorders afflict the central nervous system, among which neurodegenerative disorders such as Alzheimer’s disease, amyotrophic lateral sclerosis, Parkinson’s disease and Huntington's disease the scourge of 21st century [48]. These diseases are growing inevitably as the aging population continues to grow, and pose a severe socio-economic burden to the society. Despite the difference in the
Conclusion
To conclude, quercetin acts as an effective therapeutic agent against various neurodegenerative disorders through the suppression of oxidative stress, inflammation and enhancing neurogenesis. Evidences illustrate quercetin as a potent antioxidant, increases the neuronal survival against a variety of oxidative insults. The presence of inherent number of free hydroxyl groups in the chemical skeleton of quercetin plays an important role for its antioxidant activity. Direct and indirect antioxidant
Acknowledgements
KPD and NS gratefully acknowledge the Bioinformatics Infrastructure Facility provided by the Alagappa University (funded by Department of Biotechnology, Government of India; Grant No. BT/BI/25/015/2012). NS wishes to acknowledge University Grants Commission, New Delhi, India for the financial support through Dr. D.S. Kothari Post Doctoral Fellowship Scheme (No. F.4-2/2006(BSR)/BL/13-14/0345).
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