Quercetin is an antitumor agent; induces apoptosis and inhibits synthesis of heat shock proteins. Inhibits many enzyme systems including tyrosine protein kinase, phospholipase A₂, phosphodiesterases, mitochondrial ATPase, PI 3-kinase and protein kinase C. Can also activate Ca²⁺ and K⁺ channels and behaves as an agonist at estrogen (GPER) receptors. Blocks cellular entry by influenza A virus via an interaction with hemaglutinin. Inhibits SARS-CoV 3CL^pro (IC₅₀ = 73 μM).

Quercetin is commonly used as a expectorant drug in clinical medicine in China. This product has various kinds of pharmacological functions such as having a good expectorant, cough effect, also having certain anti-asthma effect, and having further effects of lowering blood pressure, enhancing capillary resistance, reducing capillary fragility, reducing blood fat, expansion of coronary artery, increasing coronary blood flow.
Clinically, quercetin is mainly used for treating clinical bronchitis and phlegmatic inflammation. It also has adjuvant therapy effect on coronary artery disease and high blood pressure. FDA may have some kinds of adverse reactions such as dry mouth, dizziness, and burning sensation in stomach area which may disappear after treatment.

1. It can be used as a kind of antioxidant which is mainly used for oil, drinks, cold drinks, meat processing products.
2. It has good effects of expectorant, anti-cough, anti-asthma and can be used for treating chronic bronchitis as well as for adjuvant therapy of coronary heart disease and high blood pressure.
3. It can also be used as analytical standards