Sarsparilla

Smilax officinalis
In North America it used to flavor root beer and even named a beverage toward the end of the last century. Farther south, however, it has been used for hundreds of years as a tonic and to treat various sexual maladies. The former may be explained by an infection-fighting phytohormone (plant-based hormone) that resembles cortisone. The latter, of course, is what we're interested in here.
Sarsparilla contains phytosterols, which are used by the body to create testosterone and progesterone. These hormones control agression and sex drive in both genders, so it is quite possible that medicine has vindicated the ancient use of sarsparilla to combat impotence and frigidity.