Quercetin is soluble in glacial acetic acid, alkaline, the aqueous solution is yellow, almost insoluble in water, and the ethanol solution tastes very bitter. As a natural flavonoid widely existing in nature, quercetin has been deeply studied. It has been found that it has multiple biological activities, such as antioxidant, antiviral, and anti-inflammatory effects. It can be used in cell and animal experiments to treat liver, heart, spleen, lung, kidney, orthopedic diseases, nervous system diseases, etc. Quercetin widely exists in the stem bark, flowers, leaves, buds, seeds and fruits of many plants, mostly in the form of glycosides, such as rutin, quercetin, hypericin, etc. Quercetin can be obtained by acid hydrolysis cortex. Among them, the content is higher in the stalk and leaves of buckwheat, sea buckthorn, hawthorn and onion.
Quercetin can significantly inhibit the effect of cancer-promoting agents, inhibit the growth of malignant cells in vitro, and inhibit the synthesis of DNA, RNA and protein in Ehrlich ascites cancer cells. Quercetin inhibits platelet aggregation and the release of serotonin (5-HT). Quercetin has obvious inhibitory effect on platelet aggregation induced by ADP, thrombin and platelet activating factor (PAF), among which the inhibitory effect on PAF is strong.
Quercetin is insoluble in water, so the introduction of hydrophilic groups increases solubility and facilitates absorption, thereby enhancing its pharmacological effects. Synthetic quercetin oxyacetic acid lysine salt with increased water solubility. Clinical trials have shown that quercetin has high efficacy in the treatment of bleeding disorders, circulatory disorders, and atherosclerosis.
Quercetin can be used as a medicine. Quercetin has good expectorant, antitussive effects, and has certain antiasthmatic effects for the treatment of chronic bronchitis. In addition, quercetin can also lower blood pressure, enhance capillary resistance, reduce capillary fragility, lower blood lipids, expand coronary arteries, and increase coronary blood flow.
During human exercise, exercise fatigue is related to oxidative stress. Studies before 2017 showed that exercise fatigue can lead to a decrease in the body's antioxidant capacity and oxidative stress damage. Quercetin's powerful antioxidant activity may also help relieve fatigue. Quercetin supplementation reduces lipid peroxidative damage by reducing MDA levels during exercise. In addition, quercetin improves the body's antioxidant capacity by inhibiting the reduction of SOD and GSH-Px during exercise, thereby delaying fatigue.