Plant chemicals give hope for 'alternative contraceptives'

Evrard Martin
Mai 17, 2017

And, because the chemicals aren't hormones, unlike other forms of birth control, they may dodge the unpleasant side-effects that arise from messing with complicated and delicate hormone balances in the body, such as changes in mood, weight, and libido.

Also, because the chemicals prevent fertilization, they may be a more acceptable alternative in the eyes of those who object to emergency contraceptives, such as Plan B, that prevent the implantation of a potentially viable fertilized egg.

The UC Berkeley team's primary focus of study is in reproduction, with a particular interest in the hormones that trigger hyperactivity in sperm. Fertilisation can not occur unless sperm overcome this obstacle.

Leaves from the plant are used both as an anti-fertility drug and as a remedy for rheumatoid arthritis in Chinese traditional medicine.

The key to the sperm "power kick" is the opening of a molecular gateway that allows an influx of calcium to the cell's tail, said the researchers writing in the journal Proceedings of the National Academy of Sciences.

Last year, the three researchers found that the hormone progesterone is key to opening the calcium channel and triggering tail whipping.

For the final stretch of their fertilization journey, sperm rev up their whip-like tails to ludicrous egg-boring speed.

The researchers observed that sperm affected by the chemicals was unable to generate the final "push" needed from their tails to force them through the barrier, which is needed for fertilisation to occur.

"This is also a reason, why these compounds are so expensive to purchase because it takes a significant amount of efforts to extract them from plants and enrich".

Purusing books on natural contraceptives used by indigenous peoples around the world, researchers came across several non-steroid chemicals isolated from anti-fertility plants.

One was pristimerin, from the plant Tripterygium wilfordii, also known as "thunder god vine".

For thousands of years humans have been using a vast array of odd folk contraceptive methods. While it has been tested as an anticancer agent, it was not suspected of having contraceptive properties.

"These compounds not only blocked calcium channel activation, but also blocked sperm hyperactivated motility, reducing their activity to the level of nonactivated sperm cells", Lishko said. "It is not toxic to sperm cells; they still can move", said Polina Lishko, assistant professor of molecular and cell biology from the University of California, Berkeley. "But they can not develop this powerful stroke, because this whole activation pathway is shut down".

Lishko and her colleagues are now working with researchers in OR to test how effective these chemicals are in preventing primate in vitro fertilization, since their own studies involved human sperm only.

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