A significant advancement in plant derived medicines in the last two centuries in such areas as central nervous system, anti-tumor and anti-inflammatory activities has led to the development and identification of active chemicals and understanding of their modes of action. As for man’s health related to sexuality, numerous age-old natural products have been historically claimed as ‘aphrodisiacs’ – a collective meaning, which describes improvement of arousal, libido and/or sexual energy and activity.
It is believed that phytoandrogens are weaker than androgens and therefore have lesser side effects. They are also claimed to have minimal feedback inhibition on testosterone biosynthesis. However, this has to be proven. We had the opportunity to explore and evaluate the pharmacological effects of Tribulus terrestris (TT-with about 50% of protodioscin extract as active ingredient) in our laboratory. In these studies, TT increased the proerectile relaxant effect of nitrergic (NO) neurotransmission in the rabbit corpus cavernosum and improved sexual behaviour in rats. The effects of TT were apparently due to its androgen increasing property which was mediated through NO-cGMP pathway and the second messengers viz., cAMP and cGMP. Apart from its receptoral affinity, it also compared well with the effects of testosterone in our studies.
Furthermore, TT has been shown to improve seminal parameters and fertility in some studies. Ginseng plant, ginkgo biloba, green oats extract etc have also been studied and proven to have positive responses through NO-cGMP and androgen receptoral mechanisms. However, many other phytoagents with similar potentials to improve desire or libido may require further studies to evaluate their efficacy in sexual medicine. These will be discussed in the light of the current understanding of the evidence-based, placebo controlled studies.
