Gossypol is a natural phenol derived from the cotton plant (genus Gossypium). Gossypol is a phenolic aldehyde that permeates cells and acts as an inhibitor for several dehydrogenase enzymes. It is a yellow pigment.

Among other things, it has been tested as a male oral contraceptive in China. In addition to its contraceptive properties, gossypol has also long been known to possess antimalarial properties. Other researchers are investigating the anticancer properties of gossypol.

A ***9 investigation in Jiangxi showed correlation between low fertility in males and use of crude cottonseed oil for cooking. The compound causing the contraceptive effect was determined to be gossypol.

In the ***0s, the Chinese government began researching the use of gossypol as a contraceptive. Their studies involved over *0,**0 subjects, and continued for over a decade. They concluded gossypol provided reliable contraception, could be taken orally as a tablet, and did not upset men's balance of hormones.

However, gossypol also had serious flaws. The studies also discovered an abnormally high rate of hypokalemia among subjects. Hypokalemia — low blood potassium levels — causes symptoms of fatigue, muscle weakness, and at its most extreme, paralysis. In addition, about 7% of subjects reported effects on their digestive system, and about *2% increased fatigue. Most subjects recovered after stopping treatment and taking potassium supplements. A later study showed that taking potassium supplements during gossypol treatment did not prevent hypokalemia in primates.

In the mid****0s, the Brazilian pharmaceutical company Hebron announced plans to market a low-dose gossypol pill called Nofertil, but the pill never came to market. Its release was indefinitely postponed due to unacceptably high rates of permanent infertility. Between five and twenty-five percent of the men remained azoospermic up to a year after stopping treatment. The longer the men had taken the drug and the higher their overall dosage, the more likely the men were to have lowered fertility or to become completely infertile. Researchers have suggested that gossypol might make a good non-invasive alternative to surgical vasectomy.[7]

In ***6, the Chinese stopped research because of these side effects.[citation needed]

In ***8, the World Health Organization's Research Group on Methods for the Regulation of Male Fertility recommended that research should be abandoned. In addition to the other side effects, the WHO researchers were concerned about gossypol's toxicity: the toxic dose in primates is less than *0 times the contraceptive dose. This report effectively ended further studies of gossypol as a temporary contraceptive, but research into using it as an alternative to vasectomy continues in Austria, Brazil, Chile, China, the Dominican Republic, and Nigeria.