Wild plant compounds could act as male contraceptive, researchers find

Two compounds normally found in wild plants have the potential to act as a male contraceptive, according to the results of research published in Proceedings of the National Academy of Sciences (online, 15 May 2017)^[1]
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Researchers in California discovered that lupeol, commonly found in mangoes, grapes, and pristimerin, as well as thunder god vine, a natural extract that reduces pain and inflammation and treats symptoms of rheumatoid arthritis, lupus and other autoimmune diseases, can “significantly” reduce sperm hyperactivation, preventing them from fertilising a female egg.

The study results show that the “two plant triterpenoids… can serve as promising candidates for contraception, as they reduce the number of hyperactive spermatozoa, thus preventing sperm from reaching and fertilizing an egg”.

The discovery was made during a larger study into CatSper, the calcium channel of sperm, which is essential for sperm hyperactivated mobility and fertility.

The researchers found that when pristimerin, in combination with the female hormone progesterone (P4), was applied to the sperm it reduced CatSper currents by 64%. When applied in combination with pregnenolone sulfate (PregS) – a sulfated steroid hormone similar in structure to progesterone — the current was reduced by 48%.

The effects were even greater when lupeol was applied to sperm. CatSper currents were reduced by 71% when the plant compound was used in combination with P4 and by 68% in combination with PregS.

Commenting on the research and the potential of the plant compounds to be the foundation of a future male contraceptive, Allan Pacey, professor of andrology at the University of Sheffield in its academic unit of reproductive and developmental medicine, says: “I knew the CatSper was a likely contraceptive target as this has been talked about a lot in sperm circles, but I had assumed a drug would have to be designed rather than finding some kind of herbal / plant-derived option.

“If this is to be a useful contraceptive, then the authors will need to now show it works in humans who take these compounds as a pill or injection.”