Bitter Melon

Scientific Name(s): Momordica charantia L. Family: Cucurbitaceae

Common Name(s): Bitter melon , balsam pear , bitter cucumber , balsam apple , “ art pumpkin ”, cerasee , carilla cundeamor

Clinical Overview

Uses of Bitter Melon

Bitter melon's possible effects include hypoglycemic, antimicrobial, and antifertility.

Bitter Melon Dosing

Bitter melon juice has been recommended for diabetes at daily doses of 50 to 100 mL; 900 mg of fruit given 3 times/day also has been given for the same indication. There are no clinical trials available to substantiate these doses.

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Documented adverse effects, including emmenogogue and abortifacient effects. The plant is not recommended in pregnant women because it may cause uterine bleeding and contractions or may induce abortion.

Bitter Melon Interactions

Increased hypoglycemic effect when bitter melon and chlorpropamide are coadministered.

Bitter Melon Adverse Reactions

Hypoglycemia.

Toxicology

The red arils around bitter melon seeds are toxic to children.

Botany

Bitter melon is an annual plant growing to 2 m tall. It is cultivated in Asia, Africa, South America, and India and is considered a tropical fruit. The plant has lobed leaves, yellow flowers, and edible (but bitter-tasting), orange-yellow fruit. The unripe fruit is green and is cucumber-shaped with bumps on its surface. The parts used include the fruit, leaves, seeds, and seed oil. 1 , 2 , 3

History

Bitter melon as an unripe fruit is commonly eaten as a vegetable 2 , 3 Bitter melon has been used as a folk remedy for tumors, asthma, skin infections, GI problems, and hypertension. 4 The plant has been used as a traditional medicine in China, India, Africa, and the southeastern US. 3 The plant has been used in the treatment of diabetes symptoms. In the 1980s, the seeds were investigated in China as a potential contraceptive. 1

Chemistry

Chemical constituents from whole plants, fruits, and seeds of bitter melon have been isolated and described. 5 , 6 , 7

Specifically, bitter melon contains the glycosides mormordin and charantin. Charantin is a hypoglycemic agent composed of mixed steroids. 2 , 4 A pyrimidine glycoside has also been found. 8 The alkaloid mormordicine is also present, along with a fixed oil. 1 Leaves contain iron, sodium, and vitamins including thiamine, riboflavin, niacin, and ascorbic acid. 4

An insulin-like, hypoglycemic peptide 1 “polypeptide-P” 2 is present in bitter melon. This has been isolated from the fruit, seeds, and tissue of the plant and has a molecular weight of 11,000. 9 An overview of specific antidiabetic constituents in bitter melon is available. 10

Bitter melon seeds contain 32% oil, with stearic, linoleic, and oleic acids. 4 The seeds also contain the pyrimidine nucleoside vicine, 10 the glycoproteins alpha-momorcharin and beta-momorcharin (abortifacients) and lectins. 3 Amino acid composition in seeds is described as well. 11 Insulin-like molecules also have been found in the seeds. 12

Bitter Melon Uses and Pharmacology

Beneficial effects of bitter melon have been studied and reviewed. 3 , 13 , 14 , 15 These effects include hypoglycemic, antimicrobial, and antifertility.

A review describing the antidiabetic activity of bitter melon discusses in vitro, animal, and human studies, mechanisms of action, and the phytochemicals involved. 10 The hypoglycemic effects of bitter melon have been established in animal and human studies. 16 , 17 Constituents of the plant that contribute to its hypoglycemic properties include charantin, polypeptide P, and vicine. 2 , 10 , 18 , 19 Reduction of blood glucose and improvement of glucose tolerance are the mechanisms by which the plant exerts its actions.

Animal studies document the hypoglycemic effects and include reports in diabetic mice; 20 , 21 , 22 studies in rats, 23 , 24 , 25 , 26 including improvement in glucose tolerance, 27 sustained decrease in blood glucose levels even after 15 days of discontinuation of bitter melon treatment (as well as a decrease in serum cholesterol levels), 28 and a suggested oral hypoglycemic mechanism involving the presence of viable beta cells; 29 and a study in diabetic rabbits, which also confirmed the plant's consistent hypoglycemic effects. 30

Other mechanisms for hypoglycemic effects include extrapancreatic actions such as increased glucose uptake by tissues, glycogen synthesis in liver and muscles, triglyceride production in adipose tissue, and gluconeogenesis. 31 Another report suggests the activity to be partly due to increased glucose use in the liver, rather than an insulin secretory effect. 32 Hepatic enzyme studies demonstrate bitter melon's hypoglycemic activity without glucose tolerance improvement in mice; 33 hypoglycemic activity by decreasing blood glucose synthesis through inhibition of enzymes glucose-6-phosphatase and fructose-1,6-bisphosphatase, along with enhancement of glucose oxidation by enzyme G6PDH pathway; 34 and hypoglycemic actions involving hepatic cytochrome P450 and glutathione S-transferases in diabetic rats. 35 One report finds retardation of retinopathy (a diabetic complication) in diabetic rats administered a fruit extract of bitter melon. 36 At least 1 animal study finds no hypoglycemic effects in diabetic rats given a freeze-dried preparation of the plant for 6 weeks. 37

Bitter melon improved glucose tolerance in humans. 27 Another study reported improved glucose tolerance in 18 type 2 diabetic patients with 73% success from a juice preparation of bitter melon. 38 One report observed a 54% decrease in postprandial blood sugar, as well as a 17% reduction in glycosylated hemoglobin in 6 patients taking 15 g of aqueous bitter melon extract. 2 A report is also available on patients taking a powder preparation of the plant. 39 Clinical trials using fresh fruit juice in 160 patients controlled diabetes. Bitter melon did not promote insulin secretion but did increase carbohydrate use. 4

Roots and leaf extracts of bitter melon have shown antibiotic activity. 3 , 4 One study reports cytostatic activity from bitter melon aqueous extract, 40 as constituents momorcharins have antitumor properties and can inhibit protein synthesis. 41 Similarly, the plant also inhibits replication of viruses, including polio, herpes simplex type 1, and HIV. 3 , 10 A study on antipseudomonal activity reports bitter melon to be effective, but not promising, in overall results. 42 Antiviral and other effects of bitter melon have been reviewed. 3

Research reveals no animal or clinical data regarding bitter melon as an antimicrobial agent.

A protein in bitter melon was reported to have antifertility activity in male rats. 43 Oral administration of the fruit (1.7 g/day extract) to male dogs caused testicular lesions and atrophy of spermatogenic aspects. In female mice, the plant exhibited similar, but reversible, antifertility effects. 10 Momorcharins are capable of producing abortions. 41 Uterine bleeding has been induced in pregnant rats given the juice, as well as in rabbits, but not in nonpregnant females. 10 The ripe fruit has been said to induce menstruation. 1

Research reveals no clinical data regarding bitter melon's antifertility action.

Other effects of bitter melon include dose-related analgesic activity in rats and mice, 44 anti-inflammatory actions, 10 and treatment for GI ailments, such as gas, ulcer, digestion, constipation, dysentery, 1 , 4 or hemorrhoids. 45 The plant has also been used for skin diseases (eg, boils, burns, infections, scabies, psoriasis), 4 and for its lipid effects 10 and hypotensive actions. 4 , 10 Bitter melon has also been used as an insecticide. 3 , 4 It exhibits genotoxic effects in Aspergillus nidulans . 46

Dosage

Bitter melon juice has been recommended for diabetes at daily doses of 50 to 100 mL; 900 mg of fruit 3 times /day also has been given for the same indication. There are no clinical trials available to substantiate these doses.

Pregnancy/Lactation

Documented adverse effects include emmenogogue and abortifacient effects. 47 The plant is not recommended in pregnant women because it may cause uterine bleeding and contractions or may induce abortion. 3 , 10 , 41 Avoid use.

Interactions

Both recovered upon medical treatment. 10 Increased hypoglycemic effect was noted in a 40-year-old woman taking M. charantia (a curry ingredient) and chlorpropamide. 48

Adverse Reactions

Bitter melon's hepatotoxic effects have been demonstrated in animals, in which enzymes became elevated following plant administration. The momorcharin constituents may induce morphological changes in hepatocytes as well. 10

Because of the plant's ability to reduce blood sugar, caution is warranted in patients who may experience hypoglycemia. 1 Two small children experienced hypoglycemic coma resulting from intake of a tea made from the plant. Bitter melon extract is said to be nontoxic. 3 The plant is relatively safe at low doses and for a duration of 4 weeks or less. 1 There are no published reports of serious effects in adults given the usual oral dose of 50 mL. In general, bitter melon has low clinical toxicity, with some possible adverse GI effects. 10

The seed constituent, vicine may induce “favism,” an acute condition characterized by headache, fever, abdominal pain, and coma. 3 , 10

Toxicology

The red arils around bitter melon seeds are toxic to children. The juice given to a child in 1 report caused vomiting, diarrhea, and death. 4

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