Scientific Name(s): Gymnema sylvestre (Retz.) Schult. Family: Asclepiadaceae (milkweed)
Common Name(s): Meshashringi , gurmar , merasingi , periploca of the woods
Uses of Gymnema
The plant has been used in traditional medicine, most notably to control blood glucose. Use as a lipid-lowering agent, for weight loss, and for the inhibition of caries have also been investigated, primarily in rodent studies. However, little to no clinical information is available to support the use of gymnema for any indication.
Limited controlled studies exist. Clinical studies investigating antidiabetic effects have typically used 200 or 400 mg extract daily standardized to contain 25% gymnemic acids.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
Gymnema Adverse Reactions
A case report of hepatotoxicity exists.
Information is lacking.
G. sylvestre is a woody, climbing plant indigenous to the tropical forests of central and southern India. Distribution of gymnema is worldwide, and it is recognized in the traditional medicinal literature of many countries, including Australia, Japan, and Vietnam. The opposite, elliptic/ovate leaves are most commonly used, but the stem also appears to possess some pharmacologic activity. The plant bears small, yellowish flowers. Gymnema is also known as Asclepias geminata Roxb., Gymnema melicida Edg., and Pinus sylvestris Willd. Gymnema montanum has also been investigated. 1 , 2 , 3
Gymnema has played an important role in the traditional Ayurvedic medical system for centuries, primarily confined to the management of diabetes mellitus and similar hypo/hyperglycemic conditions. The leaves have also been used for stomach ailments, constipation, water retention, and liver disease. The flowers, leaves, and fruits have been used in the treatment of either high or low blood pressure, tachycardia, and arrhythmias. Chewing the leaves destroys the ability to discriminate sweet taste, giving it the common Hindi name of gurmar or “sugar destroyer.” The plant has been used alone and as a component of the Ayurvedic compound Tribang shila , a mixture of tin, lead, zinc, G. sylvestre leaves, neem ( Melia azadirachta ) leaves, Enicostemma littorale , and jambul ( Eugenia jambolana ) seeds. As early as 1930, the pharmacologic effect of the plant was investigated. The plant is available in a number of commercial over-the-counter herbal products. 3 , 4 , 5
Gymnemic acids, a group of triterpenoid saponins, are the main class of chemical constituents isolated from G. sylvestre and are thought to be responsible for the observed antidiabetic activity. The quantity of gymnemic acids extracted from the leaves varies according to the location of cultivation and the time of harvesting; concentrations varying between 0.67% and 1.06% have been reported. Multiple gymnemic acid congeners have been identified, and high performance liquid chromatography methods for standardization have been described.
Also present in gymnema extracts are gymnemasaponins, a group of antisweet principles with a novel D-glucoside structure. The structure of gurmarin, another antisweet agent found in gymnema, has been elucidated. Gymnemosides have been isolated from alcoholic extracts of G. sylvestre leaves. Other constituents include flavones, anthraquinones, chlorophylls, phytin, resins, quercitol, alkaloids, and tannic, formic, and butyric acids. 2 , 6 , 7 , 8 , 9 , 10 , 11
Gymnema Uses and PharmacologyDiabetes
Studies suggest the hypoglycemic effects of gymnema extracts operate through a number of possible mechanisms, including reduced uptake of glucose in the small intestine, improved glycolysis, glucogen synthesis and gluconeogenesis, and stimulation of insulin release from islets of Langerhans. 3 , 12 , 13 , 14Animal data
A number of studies have evaluated the effects of G. sylvestre on blood sugar in animals, often in comparison with glibenclamide or tolbutamide. Most studies reported decreased blood glucose concentrations in diabetic rats. 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 Decreased lipid peroxidation and oxidative stress have also been demonstrated in rats. 21 , 23 , 24 , 25 , 26 In addition, taste response to sucrose, fructose, lactose, and maltose in rats was markedly suppressed by gurmarin, a protein extracted from G. sylvestre . 27 , 28Clinical data
Few methodologically sound clinical studies exist. 3 , 29 Limited, small clinical studies found decreases in mean glycosylated hemoglobin (HbA 1c ), fasting blood glucose, and mean daily preprandial plasma glucose for patients with type 1 and 2 diabetes receiving gymnema extracts in addition to their usual medication. 30 , 31 , 32Lipid-lowering
A dose-dependent increase in fecal cholesterol and cholic acid-derived bile acid excretion has been demonstrated in rats. 33 A 3-week study showed a decrease in apparent fat digestibility and an increase in excretion of neutral sterols and acidic steroids in rats receiving an extract of G. sylvestre leaves and either a normal or high-fat diet. Total serum cholesterol and triglycerides were also decreased. 34 After 10 weeks, plasma triglycerides were lower in gymnema-fed rats compared with controls, but there was no difference in plasma total cholesterol levels. 35 In diabetic rats, improved lipid profiles were observed with gymnema extract and gymnemic triacetate. 36 , 37 , 38Clinical data
Reduction in plasma cholesterol, triglycerides, and free fatty acid levels was observed in limited studies of diabetic patients who received supplements of gymnema in addition to their usual antidiabetic medication (eg, insulin, glibenclamide, tolbutamide). 30 , 31 Lipid lowering was a secondary end point in these studies, which were designed to demonstrate the antidiabetic effects of gymnema.Weight loss
Increases in body weight were suppressed in a long-term study of the administration of G. sylvestre extract to rats. 35 , 38 Conversely, in another rodent study, loss of weight was inhibited by gymnema extracts. 20Clinical data
Decreased body weight has been demonstrated in studies using combinations of various dietary supplements, including G. sylvestre with chitosan, fenugreek, and vitamin C, and gymnema with niacin-chromium complex. The resultant weight loss cannot be attributed to a single ingredient. 39 , 40Other uses
An alcoholic extract of dried leaves exhibited antibacterial activity against Bacillus pumilis , Bacillus subtilis , Pseudomonas aeruginosa , and Staphylococcus aureus . 41 Gymnemic acids A and B have demonstrated antiviral activity against the influenza virus. Other fractions lacked this activity. 6 A possible application in the prevention of dental plaque formation has been investigated, but systematic studies are lacking to confirm this use. 6Anti-inflammatory
Histamine release from mast cells was inhibited by extracts of G. sylvestre in vitro. 6 Moderate inhibition of carrageenan-induced rat paw edema occurred with an aqueous extract of G. sylvestre leaves; naproxen produced superior inhibition of edema. However, efficacy of gymnema was similar to that of naproxen in a peritoneal ascites model in mice. Unlike naproxen, gymnema did not inhibit beneficial granuloma formation; gastric mucosa was not irritated by high doses. 42Cancer
A combination product containing G. sylvestre extracts was protective against sugar-induced cataracts in rats. 46
Information regarding safety and efficacy in pregnancy and lactation is lacking. 32
None well documented.
A case report of reversible hepatotoxicity was attributed to the consumption of G. sylvestre as a tea. Toxicity was evident by laboratory indices and histology. 47 No adverse reactions were reported in 1 long-term clinical study. 30 Systolic blood pressure was raised in spontaneously hypertensive rats fed a high sucrose diet, but the clinical importance of this finding is unknown. 48
In a short-term toxicity study in mice, no gross behavioral, neurologic, or autonomic effects were observed. The acute median lethal dose (LD 50 ) was 3,990 mg/kg, and the safety ratio (LD 50 /median effective dose) was 11 and 16 in normal and diabetic rats, respectively. 18
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