The Thunder God Vine could be the key to a male contraceptive pill, according to new research. One of the compounds isolated from the vine appears to interfere with the most crucial moment of conception—when sperm meets egg—making a strong case for modern pharmacologists turning to traditional medicine for fresh ideas.
“Thunder God Vine is important to traditional Chinese medicine,” coauthor Nadja Mannowetz of UC Berkeley, who first found out about the vine in a book called Anti-fertility Plants of the Pacific, told Fatherly. The vine had been used for centuries to treat rheumatoid arthritis, Mannowetz explains, but often resulted in “reversible” infertility in men. “When they stopped taking it, they became normally fertile again. That’s really when we thought, whoa, this is crazy.”
But, as with most forms of traditional medicine, the Thunder God Vine has its problems. The extract consumed by men in China, for instance, is comprised of many different compounds some of which may be toxic. The trick for researchers was finding a way to isolate the one compound responsible for the infertility effect, to the exclusion of potential poisons. Mannowetz and her colleagues quickly tracked down a likely culprit—a compound called pristimerin.
Pristimerin seemed like a solid candidate from the get go. Another Berkeley researcher, Melissa Miller, had recently discovered a protein receptor on the tail of sperm that, when triggered, gives sperm a “power kick”, allowing it to drill into the egg’s outer layer for fertilization. When the receptor is switched on by progesterone binding the enzyme ABHD2, calcium channels open up in the sperm’s tail to give it a final, heroic tail whipping finish. “We thought, okay, we now have a molecule that directly influences this ion channel that is expressed only in sperm cells,” Mannowetz says. Pristimerin was the perfect fit—a natural compound from a vine reputed to prevent fertility, that conveniently blocks progesterone from binding with ABHD2.
In order to test their hypothesis, Mannowetz and her colleagues at the Lishko Lab exposed human sperm to pristimerin. They found that when the sperm were exposed to pristimerine and progesterone their curviliner velocity, which would normally be increased to punch through the egg, decreased by as much as 40 percent, a significant enough decrease to keep the sperm from entering. This happened due to pritimerin competeing with prgesterone at the site of the ABHD2 enzyme, keeping the switch from being flipped.
But don’t expect men to put their vasectomy plans on the shelf and head down to the pharmacists for some pristimerin anytime soon. There are plenty of hurdles yet to leap. In the immediate future, Mannowetz and her team will be working with a natural chemist from MIT to create a synthetic version of the organic compound. That will lower the costs and allow scientists to alter the chemical makeup and make the contraceptive more potent. And then there are animal tests, human trials, FDA approval—a lengthly process rife with pitfalls for candidate drugs. But ultimately, the lesson for Mannowetz is that there is a lot out there yet to be discovered. “There are many many things out there in the plant world,” she says. “And I think if we are open enough to try, it can broaden our horizons.”