Tribulus is the name of a plant genus found in many temperate regions of the world. The species most commonly known is Tribulus terrestris, also called a puncture vine, which grows widely as a weed.
Tribulus is used to make a dietary supplement which is believed to raise the natural levels of testosterone, and some studies have shown that the saponin steroids it contains can have a positive effect in stimulating the libido and erectile function in older men, and to significantly increase the sperm count in sexually active males between 21 and 50.
The main active component, tribulosin, may also have a beneficial effect on the heart by inhibiting oxidation and myocardial cell death.
Tribulus has been in use for centuries in Chinese and Ayurvedic medicine, where it was used as a remedy for fatigue as well as disorders of the reproductive and urinary tract. Traditionally, it was supposed to increase libido, sexual responses and male fertility, and so was used as an aphrodisiac.
In Europe, it was also believed that the plant could act as a stimulant to produce more testosterone, leading to its current widespread popularity as a supplement for athletes and body-builders.