Cinnamon and Bitter Melon for reducing fasting levels

Mechanism of Action of Gymnemic Acids

Gymnemic acid formulations have also been found useful against obesity, according to recent reports [10]. This is attributed to the ability of gymnemic acids to delay the glucose absorption in the blood. The atomic arrangement of gymnemic acid molecules is similar to that of glucose molecules. These molecules fill the receptor locations on the taste buds thereby preventing its activation by sugar molecules present in the food, thereby curbing the sugar craving. Similarly, Gymnemic acid molecules fill the receptor location in the absorptive external layers of the intestine thereby preventing the sugar molecules absorption by the intestine, which results in low blood sugar level [11].

G. sylvestre leaves have been found to cause hypoglycemia in laboratory animals and have found a use in herbal medicine to help treat adult onset diabetes mellitus (NIDDM). When Gymnema leaf extract is administered to a diabetic patient, there is stimulation of the pancreas by virtue of which there is an increase in insulin release [12]. These compounds have also been found to increase fecal excretion of cholesterol [13], but further studies to prove clinical significance in treating hypercholesterolemia (high serum cholesterol) are required. Other uses for Gymnema leaf extract are its ability to act as a laxative, diuretic, and cough suppressant. These other actions would be considered adverse reactions when Gymnema is used for its glucose lowering effect in diabetes.

Gymnema leaf extract, notably the peptide ‘Gurmarin’, has been found to interfere with the ability of the taste buds on the tongue to taste sweet and bitter. Gymnemic acid has a similar effect. It is believed that by inhibiting the sweet taste sensation, people taking it will limit their intake of sweet foods, and this activity may be partially responsible for its hypoglycemic effect [14].

There are some possible mechanisms by which the leaves and especially Gymnemic acids from G. sylvestre exert its hypoglycemic effects are: 1) it increases secretion of insulin, 2) it promotes regeneration of islet cells, 3) it increases utilization of glucose: it is shown to increase the activities of enzymes responsible for utilization of glucose by insulin-dependant pathways, an increase in phosphorylase activity, decrease in gluconeogenic enzymes and sorbitol dehydrogenase, and 4) it causes inhibition of glucose absorption from intestine.

The gymnemic acid components are believed to block the absorption of glucose in the small intestine, the exact action being unknown. It could be involve one or more mechanisms [14].

One of the mechanisms responsible for adult onset diabetes mellitus is a form of insulin resistance, which is attributed to the inability of insulin to enter cells via the insulin receptor. Gymnema may overcome this resistance, but require further studies to confirm its validity and also whether the effect is clinically relevant. Should this effect be proven, Gymnema may prove useful in both adult onset (NIDDM) and juvenile onset diabetes mellitus (IDDM) to help insulin enter cells. In the case of IDDM, the insulin is injected by syringe and is not secreted from the pancreas [15].

The leaves are also noted for lowering serum cholesterol and triglycerides. The primary chemical constituents of Gymnema include gymnemic acid, tartaric acid, gurmarin, calcium oxalate, glucose, stigmasterol, betaine, and choline. While the water-soluble acidic fractions reportedly provide the hypoglycemic action, it is not yet clear what specific constituent in the leaves is responsible for the same. Some researchers have suggested gymnemic acid as one possible candidate, although further research is needed [16]. Both gurmarin (another constituent of the leaves) and gymnemic acid have been shown to block sweet taste in humans. The major constituents of the plant material 3B glucuronides of different acetylated gymnemagenins, gymnemic acid a complex mixture of at least 9 closely related acidic glucosides [17–19].

The following figure could provide a diagrammatic representation for explaining the action of gymnemic acids on the intestinal receptors. The basic function of the acids is to bind to the receptor on the intestine, and stop the glucose molecule from binding to the receptor. Thus, gymnemic acids prevent the absorption of excess glucose.

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