Extracts of Momordica charantia, a cucumber-like plant from East Africa and Asia, have an anabolic effect. Indian researchers gave extracts to male rats and observed that the animals' muscles grew.
The Indians' study dates from 1998, but that doesn't make it any less interesting. It was intended to identify substances for contraceptives manufacturers: local healers sometimes use Momordica charantia to induce an abortion. During the study it became clear that there are naturally occurring substances that have an anabolic effect. The supplements industry caught on to this and processes extracts from this plant in bodybuilding products.
Momordica charantia is the Latin name for Karela, Bitter Gourd or Bitter Melon. Fairly pure extracts of Momordica charantia are to be found in supplements intended to lower blood-sugar levels. In fact hypoglycaemia, along with vaginal bleeding, is a side effect of Momordica charantia that users should bear in mind. The most important active ingredient of Momordica charantia is probably the steroid charantin. [Structural formula shown below]
The researchers made benzene-, alcohol- and petroleum ether-based extracts of the seeds of the plant. They gave this either orally or through injections to rats, for a period of five weeks. The dose used was 250 mg per kg bodyweight per day.
The animals reacted as though they had been given steroids. Their testes became lighter and contained more cholesterol at the end of the five weeks. This was probably because they produced less testosterone as a result of a decrease in concentration of the hormones FSH an LH, the researchers suggest. The animals' sperm count went down drastically.
The figure below shows what the extracts did to the prostate and the levator ani muscle. These effects are taken as representative of the masculinising and anabolic effects of steroids. The first figure shows the effects of oral administration, the second the effects of injections. The amounts used were the same in both cases. The unit is milligrams per hundred grams bodyweight.
The alcohol extracts produced the most interesting results for oral users. Their anabolic effect is pretty big, but the effect on the prostate is low.
J Ethnopharmacol. 1998 May;61(1):9-16.