Over half a century after the female birth control pill arguably kickstarted a sexual revolution, men still don't have an equivalent drug-based contraceptive. Outside of condoms and vasectomies, the male contraceptive still strangely eludes researchers. Some argue it's because the biological foundations of male fertility are harder to simply block, while others suggest the success of female contraception led to a lack of interest in pharmaceutical development.

As with most things, the truth probably lies somewhere in the middle, but in recent years progress toward a male "pill" has progressed rapidly. This year, a landmark human clinical trial is starting for the most promising male contraceptive development in years, a topical gel that blocks the production of sperm. If it ultimately works it will demand the correct application of a volume of gel on a man's arms and shoulder's every day, so it certainly isn't as simple as swallowing a pill.

Finding a simple male contraceptive compound that is safe, effective and reversible has been relatively elusive for scientists, but a new study has revealed that the secret to a male birth control pill may lie in a plant extract that has ancient African origins.

Ouabain is a compound found in two types of African plants. It is also produced in very low levels in mammals. For thousands of years, the compound was used throughout Eastern Africa as a poison for arrow tips for hunting, and it was also used in battle as an arrow poison by various tribes against colonial invaders such as the Portuguese and the British.

As well as causing cardiac arrest, ouabain has been observed to dramatically decrease the motility of sperm but of course its poisonous nature has limited any contraceptive uses – until now.

A team of chemists has successfully created a synthetic ouabain analog that only zeroes in on the protein it needs to disable sperm activity, and not any other proteins that can damage heart tissue. In animal studies this new ouabain analog effectively interfered with a sperm's ability to swim and showed no toxic side effects.

The compound is also suggested to only have temporary contraceptive effects as it binds to mature sperm cells, meaning new sperm cells produced after one stops taking the compound will be motile and unaffected.

Be it a gel or a pill, it seems a viable male contraceptive drug is still some years away and questions do remain over whether men are even willing to embrace a form of birth control similar to women. Recent surveys suggest anywhere from 25 percent to 50 percent of men would be willing to take some kind of hormonal contraceptive, so this could be a useful and important area of research.

The new study was published in the Journal of Medicinal Chemistry.