A Comprehensive Review of the Phytochemical, Pharmacological, and Toxicological Properties of Tribulus terrestris L.

The general spread of Tribulus terrestris L. (South Africa, Australia, Europe, and India), the high content of active ingredients (in particular sterol saponins, as well as flavonoids, tannins, terpenoids, phenol carboxylic acids, and alkaloids), and its frequent uses in folk medicine, and as food supplements highlight the importance of evaluating its phytopharmacological properties. There are miscellaneous hypotheses that the species could have a high potential for the prevention and improvement of various human conditions such as infertility, low sexual desire, diabetes, and inflammatory diseases. Worldwide, numerous herbal supplements are commercialized with indications mostly to improve libido, sexual performance in both sexes, and athletic performance. Phytochemical studies have shown great disparities in the content of active substances (in particular the concentration of furostanol and spirostanol saponoside, considered to be the predominant active ingredients related to the therapeutic action). Thus, studies of experimental pharmacology (in vitro studies and animal models in vivo) and clinical pharmacology (efficacy and safety clinical trials) have sometimes led to divergent results; moreover, the presumed pharmacodynamic mechanisms have yet to be confirmed by molecular biology studies. Given the differences observed in the composition, the plant organ used to obtain the extract, the need for selective extraction methods which are targeted at the class of phytocompounds, and the standardization of T. terrestris extracts is an absolute necessity. This review aims to highlight the phytochemical, pharmacological, and toxicological properties of T. terrestris, with a focus on the contradictory results obtained by the studies conducted worldwide.