Antioxidants stop oxidants (free radicals, which disrupt the integrity of other molecules by stripping their electrons) from attacking nearby molecules, such as mitochondria, membranes, and DNA. There are many classes of dietary antioxidants, and flavonoids are one of them. Flavonoids have many phenols linked to their antioxidants. Common sources of flavonoids are vegetables, fruits, and beverages such as wine and teas. Of the many flavonoid powerhouses, Quercetin is a major player. Quercetin is the most widely consumed flavonoid in the diet. Quercetin has been widely used by Russians and Europeans to treat a variety of ailments.
Mechanism of Action
Pain and Inflammation
Quercetin decreases the production of the inflammatory mediators by inhibiting key enzymes called cyclooxygenases and lipoxygenase, which form proinflammatory eicosanoids (local microhormones) such as PGE2 and PGE2 alpha. The mechanism is similar to that of aspirin and indomethacin. Mediators such as histamine, bradykinin and PGE2 all potentiate pain through sensitization of afferent pain endings (the nerves that transmit impulses to the CNS and brain). Basically, these inflammatory mediators cause the body's pain receptors to become more sensitive. Quercetin, however, prevents the formation of those inflammatory mediators.
Quercetin counters allergic reactions by inhibiting enzymes responsible for the production of inflammatory mediators. Also, Quercetin inhibits histamine release by stabilizing basophils and mast cells. Quercetin is widely used by those who suffer from constant allergies (such as dust) and seasonal allergies (such as hay fever).
In a study that was released, a longitudinal investigation of risk factors for chronic diseases in elderly men revealed that high intakes of quercetin and other flavonoids predicted lower mortality rates and incidences of heart attack (myocardial infarction). Researchers in the Netherlands believe it is possible that quercetin and other flavonoids reduce risk of heart disease by lowering the formation of plaque-building substances, specifically oxidized low density lipoprotein (LDL).
Many of the complications associated with diabetes, such as glaucoma, cataracts, and neuropathy, are caused by the sorbitol pathway, a process through which high levels of glucose are converted to sorbitol and fructose via the enzyme aldose reductase. In experimental animals, inhibitors of aldose reductase reduce the kidney and neurological symptoms shown to increase with diabetes. Quercetin is an established aldose reductase inhibitor.