Traditionally used for
- Eye health
- Colds & fever
- Digestion
- Bowel health
- Mood & calm
- Skin
Cautions & contraindications
- Pregnancy
- Diabetes
☯ TCM Properties
Clears Summerheat, improves eyesight and Removes toxicity
Traditional Chinese Uses
Ku Gua is the fruit of Momordica charantia, bitter melon. Bitter and cold, entering the Heart, Spleen and Stomach channels, it clears Summerheat, brightens the eyes and resolves toxicity. It is used for Summerheat patterns and heatstroke with irritability and thirst, febrile thirst, Damp-Heat dysentery, red swollen painful eyes, and Fire-toxin sores, boils and erysipelas; it also has widespread folk use as a food and remedy for wasting-thirst (xiao ke, diabetes). It is eaten as a vegetable, decocted (about 6–15 g), or charred and powdered.
Being markedly cold and bitter, it is avoided in Spleen-Stomach cold-deficiency. The seeds are more toxic than the flesh, and use is cautioned in pregnancy.
Western Herbalism Properties
Relationships
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Botanical Description
Ku Gua is the fruit of Momordica charantia L. (Cucurbitaceae), bitter melon or bitter gourd, an annual climbing or trailing vine native to tropical Asia and widely cultivated across China, India, Southeast Asia, the Caribbean, and Africa. The slender, ridged stems bear simple tendrils and alternate, deeply 5–7-lobed, palmately veined leaves 4–12 cm wide. Plants are monoecious with solitary, pale-yellow, five-petaled flowers on long peduncles. The fruit is an oblong to fusiform pepo 8–25 cm long, conspicuously warty and ribbed, green when immature and turning orange-yellow at maturity, splitting into three valves to expose a crimson aril surrounding flat, sculpted seeds. Immature fruits are intensely bitter from cucurbitacins and the steroidal glycoside charantin; harvested fresh or sliced and dried. Used to clear summer-heat in TCM, as a hypoglycemic in Ayurveda (karela), and widely investigated in modern phytomedicine for blood-glucose effects.
Active Constituents
Charantin
Steroidal glycoside mixture (sitosteryl and stigmasteryl glucosides)The steroid glucoside fraction traditionally named as the hypoglycaemic principle of the fruit. It is a mixture rather than a single compound, which is one reason commercial bitter melon products standardised to charantin are not comparable with one another.
Polypeptide-p (plant insulin)
Insulin-like polypeptideAn insulin-like polypeptide isolated from fruit and seed. It is a protein and is not expected to survive oral digestion intact, so its relevance to an orally taken fruit or juice is uncertain despite its frequent citation.
mcIRBP-19
Insulin receptor-binding peptideA short peptide that binds the insulin receptor and is the standardisation marker for the fruit extract used in the 2022 randomised placebo-controlled trial in type 2 diabetes. It is the one bitter melon constituent with a human trial built specifically around its content.
Momordicosides
Cucurbitane-type triterpenoid glycosideThe main triterpenoid glycoside series of the fruit and a principal contributor to its bitterness. Individual momordicosides are reported to act on AMP-activated protein kinase in cell and rodent models.
Momordicine I and momordicine II
Cucurbitane-type triterpenoidBitter cucurbitane aglycones of the fruit and leaf. Their concentration rises markedly with fruit maturity and with plant stress, so a batch that tastes unusually bitter is a chemically different drug from a mild one.
Vicine
Pyrimidine glycoside (aglycone divicine)Concentrated in the seed. Beta-glucosidase hydrolysis releases divicine, which redox-cycles and depletes reduced glutathione in red cells. In a person with glucose-6-phosphate dehydrogenase deficiency this can precipitate a favism-like haemolytic crisis; it is the single most important reason to keep seeds out of the preparation.
alpha-Momorcharin and beta-momorcharin
Type I ribosome-inactivating proteinSeed proteins with documented abortifacient activity in animal models, reported to induce early and mid-term abortion and, for beta-momorcharin, to disrupt blastocyst hatching, attachment and trophoblast outgrowth. Their presence underlies the contraindication in pregnancy.
MAP30 (Momordica anti-HIV protein of 30 kDa)
Type I ribosome-inactivating proteinA seed ribosome-inactivating protein with antiviral and cytotoxic activity in vitro. Ribosome-inactivating proteins are cytotoxic by mechanism, and there is no human evidence supporting a therapeutic use of the seed on this basis.
⚠ Drug Interactions
Antidiabetic drugs (metformin, sulfonylureas such as glibenclamide, insulin)
This is a genuine pharmacodynamic interaction, not a theoretical one. In a randomised four-week trial in newly diagnosed type 2 diabetes, bitter melon lowered fructosamine in a dose-dependent way, with the 2000 mg/day arm producing a significant fall, although the effect was smaller than that of metformin 1000 mg/day. A 2022 randomised, double-blind, placebo-controlled trial of an mcIRBP-19-standardised fruit extract also reported glucose lowering. The Cochrane review found the trial evidence insufficient to recommend bitter melon as a treatment, but insufficient efficacy evidence does not remove the additive-hypoglycaemia risk when it is stacked on top of a working drug regimen.
Clinical note: If a patient on glucose-lowering drugs starts or stops bitter melon, expect to review the drug dose and have them monitor capillary glucose more often for the first two weeks. Warn about hypoglycaemia symptoms, particularly with sulfonylureas or insulin.
Glucose-6-phosphate dehydrogenase deficiency and oxidant drugs (primaquine, dapsone, nitrofurantoin, rasburicase)
The seeds contain vicine, whose aglycone divicine depletes reduced glutathione in erythrocytes by the same route as the fava bean compounds that cause favism. Red cells lacking G6PD cannot regenerate glutathione and lyse. A published systematic review of harms in humans records a G6PD-deficient man who developed haemolysis after increased consumption of a Momordica charantia tea. Adding an oxidant drug on top compounds the same insult.
Clinical note: Ask about G6PD deficiency and Mediterranean, African, Middle Eastern or South East Asian ancestry before prescribing, and do not give bitter melon, and especially not seed-containing preparations, to a G6PD-deficient patient. Never give it to a neonate.
Use during pregnancy, and drugs used in assisted conception or fertility treatment
Alpha- and beta-momorcharin isolated from the seed are documented abortifacient proteins in animal models, inducing early and mid-term abortion, and beta-momorcharin disrupts blastocyst hatching, attachment and trophoblast outgrowth. Seed and fruit extracts also produce dose-dependent antifertility effects in animals: seed extracts reduced seminiferous tubule diameter, spermatid density, daily sperm production and sperm motility in male rats, and fruit and leaf preparations produced antifertility effects in females. All of this is animal data; there is no human trial, and none is ethically possible.
Clinical note: Contraindicated in pregnancy and in couples actively trying to conceive. Culinary quantities of the cooked fruit are a different exposure from concentrated seed-containing extracts, but the safe course during pregnancy is to avoid the medicinal preparation entirely.
Bitter gourd (Ku Gua) taken together with bitter bottle gourd (Ku Hu Lu, Lagenaria siceraria) juice
Raw juice mixtures of bottle gourd and bitter gourd are a popular folk regimen for diabetes in South Asia, and the Indian Council of Medical Research investigation of bitter bottle gourd juice toxicity documented such mixed-juice consumption among the affected cases, three of whom died. The toxic principle is the cucurbitacin content of the bitter bottle gourd, not of Momordica; the hazard is that the mixture masks the warning bitterness and that the drinkers are typically elderly diabetics, the group in which the fatal cases occurred.
Clinical note: Advise patients explicitly against raw bottle-gourd-and-bitter-gourd juice regimens for diabetes, and tell them to stop and seek help immediately if any gourd juice tastes intensely bitter.
Antihypertensive and diuretic drugs
Gastrointestinal upset, abdominal pain and diarrhoea are the commonest adverse effects reported for bitter melon in the human harms review. Any resulting fluid loss is additive with diuretic therapy. There is no controlled interaction study, and no direct blood-pressure-lowering effect is established.
Clinical note: Reduce the dose if the patient reports loose stools, and consider withholding during acute illness.
Evidence Tier
Strong evidence · 5 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
3
0 verified · 3 unverified
Randomized controlled trial
2
0 verified · 2 unverified
Show 2 studies
Other clinical trial
0
Observational / case report
0
In vitro / animal
0
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Hypoglycemic effect of bitter melon compared with metformin in newly diagnosed type 2 diabetes patients
A four-week randomised trial in newly diagnosed type 2 diabetes comparing bitter melon at 500, 1000 and 2000 mg per day with metformin 1000 mg per day. A significant decline in fructosamine was seen at 2000 mg per day, but the effect was less than that of metformin. This is the trial most often cited as establishing a real, dose-related glucose-lowering effect for the fruit, and therefore the basis for treating the interaction with antidiabetic drugs as clinically meaningful.
Momordica charantia for type 2 diabetes mellitus
The Cochrane review of randomised trials of Momordica charantia in type 2 diabetes concluded that there was insufficient evidence to recommend its use, with the available trials small, short and at risk of bias. Practitioners should read the efficacy claim as unproven while still treating the additive-hypoglycaemia interaction as real.
The effect of bitter melon (Mormordica charantia) in patients with diabetes mellitus: a systematic review and meta-analysis
A systematic review and meta-analysis of randomised trials of bitter melon in diabetes. The pooled analysis did not demonstrate a convincing glycaemic benefit over placebo, reinforcing that the drug interaction rather than the efficacy claim is what a practitioner most needs to act on. Note that the published title spells the genus as Mormordica.
A randomized, double-blind, placebo-controlled trial to evaluate the hypoglycemic efficacy of the mcIRBP-19-containing Momordica charantia L. fruit extracts in the type 2 diabetic subjects
A randomised, double-blind, placebo-controlled trial of a Momordica charantia fruit extract standardised to its content of the insulin-receptor-binding peptide mcIRBP-19 in people with type 2 diabetes, reporting glucose lowering versus placebo. It applies to that standardised extract, not to bitter melon fruit, juice or capsules in general.
Harms of Momordica charantia L. in Humans; a Systematic Review
A systematic review of reported harms of Momordica charantia in humans. Gastrointestinal complaints predominate, and the review also records haemolysis in a G6PD-deficient man after increased consumption of a Momordica charantia tea, together with hypoglycaemia and reports in children. It is the most directly useful safety source for this herb.
Historical Texts
Jiu Huang Ben Cao (Herbal for Famine Relief), Zhu Su
Ming dynasty, 1406Ben Cao Gang Mu (Compendium of Materia Medica), Li Shizhen
Ming dynasty, 1596References
- Serhat S. Çiçek. Momordica charantia L.—Diabetes-Related Bioactivities, Quality Control, and Safety Considerations . Frontiers in Pharmacology (2022) [DOI]
- Sharanabasappa A. Patil, Saraswati B. Patil. Toxicological studies of Momordica charantia Linn Seed extracts in Male Mice . International Journal of Morphology (2011) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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