How It WorksTribulus terrestris is an herb that has been used in the traditional medicine of China and India for centuries. In the mid-1990s, tribulus became more well known in North America for its energy and libido properties. The active compounds in tribulus are called saponins. Two types, called furostanol glycosides and spirostanol glycosides, appear to be involved with the effects of tribulus. A serving of new Tribulus Fuel offers 625 mg of tribulus terrestris standardized for a minimum 40% (250 mg) saponins. It"s a high quality, purified and fast acting form of tribulus clinically tested for effectiveness.