The leaves of an African plant chewed for its legendary power to boost male fertility may, according to the first scientific study of its compounds, do just that.
The leaves of the khat plant, cultivated in eastern Africa and the Middle East, are prized not only because their ingredient cathinone induces mild euphoria but because users believe khat increases sexual potency. Cathinone quickly breaks down in the body into compounds similar to amphetamine stimulants called phenylpropanolamines (PPAs). That explains the euphoria reported by khat chewers but not the effect on fertility. There are, however, anecdotal reports among animal breeders of khat leaves increasing animal fertility. To get to the bottom of khat's sexy reputation, Lynn Fraser and Susan Adeoya-Osiguwa, reproductive biologists at King's College London, incubated both mouse and human sperm in a solution of PPAs similar in concentration to that in the blood of khat chewers. They then tested the sperm to see if their performance was affected.
PPAs turn out to be perfect sperm enhancers, the team reported here Monday at the 20th meeting of the European Society of Human Reproduction and Embryology. PPAs sped up sperm maturation and stimulated newly mature sperm to produce more cyclic adenosine monophosphate (cAMP), a small molecule required for the long swim up the uterus. As the sperm became fully mature, the researchers found, the burst of cAMP was inhibited, which is probably a good thing: Sperm would quickly burn out if cAMP was constantly stimulated.
The overall effect of PPAs, says Fraser, should be an increase in the proportion of sperm in semen that have the ability to make it to the egg and fertilize it. While Fraser advises against chewing khat leaves because of side effects, including gut problems brought on by the leaves' tannins, she notes that many PPAs are already approved for other medicinal uses, so a PPA fertility drug could be right around the corner.
PPAs have been known to increase the volume of ejaculation, says Rex Hess, a reproductive biologist at the University of Illinois, Urbana-Champaign, but he is impressed by their direct molecular action on sperm. Hess says the compounds could be particularly useful for perking up sperm for in vitro fertilization.