Pharmacological activity quercetin

The leafy parts of the herb contain naphthodi-anthrones (e.g., hypericin), flavonoids (e.g., quercetin), and phloroglucinols (e.g., hypaphorine). Although this herb is now commonly standardized for its hypericin content, it appears that its other constituents may also be just as pharmacologically active. 

Flavonoids are important group of polyphenols, widely distributed in plant flora. 4,000 flavonoids are known to exist and some of them are pigments in higher plants. Quercetin, kaempferol and quercitrin are common flavonoids present in nearly 70 percent of the plants. Soya flavones have recently gained importance due to variety of pharmacological activities. 

The drug contains peculiar chemical constituents such as naphtodianthrones (hypericins), acylphloroglucinols (hyperforins), flavonol glycosides (quercetin derivatives) and biflavones [9] and all the metabolites as a whole seem to contribute to its pharmacological activity. Current use of St. John s Wort is mainly for the treatment of mild to moderate depression [10,3] and drug extracts for antidepressant applications have become increasingly popular. 

Flavonoid analysis has also been carried out in propolis, another beehive product rich in flavonoids, which are partly responsible for its pharmacological activity.Qualitative and quantitative analyses were performed by using a reversed-phase column and iso-cratic elution with water-methanol-acetic acid (60 75 5) and by monitoring at 275 and 320 nm. The propolis sample was cut into small pieces, extracted with boiling methanol, and the methanolic extract was then diluted with water and, subsequently, extracted with light petroleum and diethyl ether. The last extract contained the propolis flavonoids pinocembrin (21.4%), galangin (5%), chrysin (4.8%), quercetin (2.2%), and tectochrysin (1.1%). 

If K+ channels are inhibited, cancer cell proliferation is impaired, whereas if K+ channel activities are enhanced, cancer cell growth is promoted. One exception is quercetin it has been reported to block Kv channels (Rouzaire-Dubois et al. 1993) and to activate BKca as well (Cogolludo et al. 2007 Kuhlmann et al. 2005). Pharmacological tools opened the way toward the understanding of the role of K+ channels in cell proliferation... 

Bioavailabihty of quercetin Problems and promises 13CMD2572. Biochemical and pharmacological characterization of isatin and its derivatives From structure to activity 13PR313. 

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