Icariin is a member of the class of flavonols that is kaempferol which is substituted at position 8 by a 3-methylbut-2-en-1-yl group and in which the hydroxy groups at positions 3, 4', and 7 have been converted to the corresponding 6-deoxy-alpha-L-mannopyranoside, methyl ether, and beta-D-glucopyranoside, respectively. A phoshphodiesterase-5 inhibitor, it is obtained from several species of plants in the genus Epimedium and is thought to be the main active ingredient of the Chinese herbal medicine Herba Epimedii (yinyanghuo). It has a role as an antioxidant, a bone density conservation agent, an EC 3.1.4.35 (3',5'-cyclic-GMP phosphodiesterase) inhibitor and a phytoestrogen. It is a member of flavonols and a glycosyloxyflavone.
