Maca Root (Lepidium meyenii) Dubbed by the Miami Herald as "Peru's natural Viagra," maca's radish-like root has long been reputed to increase strength, energy, stamina, libido and sexual function. Today, as researchers and physicians explore both the phytochemistry and biological activity of the plant, historical claims made for maca appear to be true. Maca root is a rich source of sterols, including sitosterol, campestrol, ergosterol, brassicasterol and ergostadienol. It is unknown exactly, which of the root's constituents affect sexual desire and performance. Two groups of novel compounds, macamides and macaenes, appear especially active and are also being investigated.

Muirapuama (Ptychopetalum olacoides) Few reputed health-enhancing plants are as popular or as widely consumed among the natives of the northern Amazon river basin as the bark of muirapuama. For centuries, this plant has been used to increase libido and improve sexual potency. The harvest and sale of muirapuama is big business throughout Brazil. As one Amazonian herbalist told me, "Muirapuama makes you sexually young again." Although research on muirapuama is still modest, reports in scientific journals and at conferences have indicated that the herb does enhance sexual desire and performance. Chemists have identified a group of sterols, including beta-sitosterol, thought to be responsible for the herb's effects. In one French study using muirapuama, 51 percent of 262 men with erectile problems reported improvement, and 62 percent experienced an increase in libido.