Bitter Melon grows in tropical areas, including parts of the Amazon, east Africa, Asia, and the Caribbean, and is cultivated throughout South America as a food and medicine. All parts of the plant, including the fruit, taste very bitter.
Medicinally, the plant has a long history of use by the indigenous peoples of the Amazon. A leaf tea is used for diabetes, to expel intestinal gas and as an antiviral for measles, hepatitis, and feverish conditions. In Brazilian herbal medicine, bitter melon is used for tumors, wounds, rheumatism, malaria, vaginal discharge, inflammation, menstrual problems, diabetes, colic, fevers and worms. In Nicaragua, the leaf is commonly used for stomach pain, diabetes, fevers, colds, coughs, headaches and malaria.
Bitter melon contains an array of biologically active plant chemicals including triterpenes, proteins, and steroids. One chemical has clinically demonstrated the ability to inhibit the enzyme guanylate cyclase that is thought to be linked to the cause of psoriasis and also necessary for the growth of leukemia and cancer cells. In addition, a protein found in bitter melon, momordin, has clinically demonstrated anti-cancerous activity against Hodgkin's lymphoma in animals. Other proteins in the plant, alpha- and beta-momorcharin and cucurbitacin B, have been tested for possible anti-cancerous effects.
In numerous studies, at least three different groups of constituents found in all parts of bitter melon have clinically demonstrated hypoglycemic (blood sugar lowering) properties or other actions of potential benefit against diabetes mellitus. These chemicals that lower blood sugar include a mixture of steroidal saponins known as charantins, insulin-like peptides, and alkaloids. The hypoglycemic effect is more pronounced in the fruit of bitter melon where these chemicals are found in greater abundance.
To date, close to 100 in vivo studies have demonstrated the blood sugar-lowering effect of this bitter fruit. The fruit has also shown the ability to enhance cells' uptake of glucose, to promote insulin release, and to potentiate the effect of insulin.
In other in vivo studies, bitter melon fruit and/or seed has been shown to reduce total cholesterol. In one study, elevated cholesterol and triglyceride levels in diabetic rats were returned to normal after 10 weeks of treatment.
In addition to these properties, leaf extracts of bitter melon have demonstrated broad-spectrum antimicrobial activity. Various extracts of the leaves have demonstrated in vitro antibacterial activities against E. coli, Staphylococcus, Pseudomonas, Salmonella, Streptobacillus, and Streptococcus; an extract of the entire plant was shown to have antiprotozoal activity against Entamoeba histolytica. The fruit and fruit juice have demonstrated the same type of antibacterial properties and, in another study, a fruit extract demonstrated activity against the stomach ulcer-causing bacteria Helicobacter pylori.
Many in vivo clinical studies have demonstrated the relatively low toxicity of all parts of the bitter melon plant when ingested orally. The fruit and leaf of bitter melon have demonstrated an in vivo antifertility effect in female animals; and in male animals, to affect the production of sperm negatively and should therefore not be used by those undergoing fertility treatment or seeking pregnancy.