test method:hplc. synonyms:3,5,7,3’,4’,-pentahydroxyflavone . herb source:the commonest flavonoid in higher plants ,usually present in glycosidic form (see rutin,isoquercitrin.quercitin,hyperin and quercimeritrin),but also isolated free from the families compositae,passiflorae,rhamnsceae and solanaceae. molecular formula: c15h10o7; molecular weight: 302.23 . physics properties:yellow needle crystal . pharmacology function:inhibits many enzymes ,e.g.,protein kinase c,lipogenases ,lens aldose reductase,3’,5’,-cyclic adenosine monophosphate phosphodiesterases,it is a radical scavenger,quercetin also in hibits smooth muscle contraction ,and proliferation of rat lymphocytes .it is antibacterial,antiviral and antihepatotoxic,and shows some mutagenic activity and allergenic properties.