Quercetin is a phenolic antioxidant and has been shown to inhibit lipid peroxidation. The putative anti-ulcer and gastroprotective effects of quercetin may, in part, be accounted for by this activity. In vitro and animal studies have shown that quercetin inhibits degranulation of mast cells, basophils and neutrophils. Such activity could account, in part, for quercetin’s putative anti-inflammatory, anti-allergy and immunomodulating activities. Other in vitro and animal studies suggest that quercetin inhibits
tyrosine kinase and nitric oxide synthase and that it modulates the activity of the inflammatory mediator, NF-kappaB. The mechanisms of anti-viral (in some cases enhanced with vitamin C) and anti-cancer activity that have
been observed, again in in vitro and in animal studies, are unknown.
Quercetin can be found in onions, apples, green tea, and black tea. Smaller amounts are found in leafy green vegetables and beansAldose reductase, also known as alditol: NADP+ oxidoreductase, is the first enzyme of the polyol pathway. Hyperglycemia enhances the flow rate of the polyol pathway and this has been linked to such diabetic complications as cataracts, retinopathy, neuropathy and nephropathy. Quercetin is known to inhibit aldose reductase.
INDICATIONS AND USAGE
It has been claimed that quercetin protects against heart attacks and stroke, but recent research found no support for this claim. Quercetin may, however, have benefit in some allergies, in conditions characterized by capillary fragility, in chronic prostatis and in some cancers. It may have beneficial effects on immunity and may have gastro-protective effects. It may also protect against the development of such diabetic complications as cataracts, retinopathy, neuropathy and nephropathy