Contraceptive pill made from olives can prevent pregnancy, scientists say

Folk contraceptives lead researchers to drugs that block fertilization

Folk contraceptives lead researchers to drugs that block fertilization

The chemicals work by blocking the activation of a calcium ion channel in the sperm, which charge up their tails for final turbo thrusts. Another chemical, primisterin, which is found in the thunder god vine used in Chinese medicine, has the same effect.

The chemicals are effective at low doses that seem to have no adverse effect on egg or sperm, other than to prevent the sperm from pushing through the cells that congregate around the egg and an enveloping membrane called the zona pelucida. At this point, sperm's movement switches to more of a whip-like motion to drive through the cell cluster and into the egg for fertilization.

Compounds extracted from two plants, thunder god vine and aloe, prevent hyperactivation in sperm, the power kick necessary to fertilize the egg. Human sperm take about five to six hours to mature once they enter the female reproductive system, which is enough time for the drug to enter the system and block the kick. They found that while progesterone could open the ion channel-powering up the tails-other hormones, namely testosterone, estrogen, and hydrocortisone, a stress hormone, blocked the channel from opening in the presence of progesterone.

The chemicals could serve as an emergency contraceptive taken either before or after intercourse, or as a permanent contraceptive via a skin patch or vaginal ring, say researchers at the University of California, Berkeley. "If one can use a plant-derived, non-toxic, non-hormonal compound in lesser concentration to prevent fertilization in the first place, it could potentially be a better option".

Another incidental discovery from the team's research was that high levels of testosterone and cortisol in a woman's body also blocked the ABHD2 protein.

The team also scanned through books on natural contraceptives used by indigenous people and pinpointed pristimerin and lepeol as non-steroid chemicals that could be isolated from anti-fertility plants. It has also been used as a folk remedy for rheumatoid arthritis.

Both pristimerin and lupeol stopped progesterone opening the vital calcium channel, the scientists discovered.

The other chemical, lupeol, is found in mango, aloe and dandelion root plants, and has been tested as an anticancer agent. The researchers are now working on animal experiments to test the potential contraceptive.

Co-author Dr Polina Lishko said: 'It is not toxic to sperm cells - they still can move. "But they can not develop this powerful stroke, because this whole activation pathway is shut down", said Lishko.

Prof Lishko and her colleagues are now going to test how well these chemicals work in primates, whose sperm cells work in a similar way to humans.

They also are searching for a cheap source of the chemicals, which are very expensive to extract from wild plants because they are present at very low levels.

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