Used for over 2,000 years, horny goat weed is any of several species of epimedium (brevicorum, sagittatum and grandiflorum), a leafy plant which grows profusely in the wild, most abundantly at higher altitudes. The leaves of the plant contain a variety of flavonoids, polysaccharides, sterols and an alkaloid called magnaflorine. One of the flavonoids, icariin, is believed to play a role in the sex-boosting effects of the plant, which is used to restore sexual fire, boost erectile function, allay fatigue, and alleviate menopausal discomfort.