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Gymnema sylvestre

Gymnema sylvestre R.Br. is a herb native to the tropical forests of southern and central India where it has been used as a naturopathic treatment for diabetes for nearly two millennia.Sanskrit Name : Meshasringi, Madhinasini or madhoolika, Hindi: Gurmar, Tamil and Malayalam Name (കുടം‌പുളി): Sirukurinchaan(சிறுகுரிஞ்சான்), Amudhapushpam, Chakkarakkolli.

Description

Large climbers, rooting at nodes, leaves elliptic, acuminate, base acute to acuminate, glabrous above sparsely or densely tomentose beneath; Flowers small, in axillary and lateral umbel like cymes, pedicels long; Calyx-lobes long, ovate, obtuse, pubescent; Corolla pale yellow campanulate, valvate, corona single, with 5 fleshy scales. Scales adnate to throat of corolla tube between lobes; Anther connective produced into a membranous tip, pollinia 2, erect, carpels 2,unilocular; locules many ovuled; Follicle long, fusiform1

Chemical composition

The major bioactive constituents of Gymnema sylvestris are a group of oleanane type triterpenoid saponins known as gymnemic acids. The latter contain several acylated (tigloyl, methylbutyroyl etc.,) derivatives of deacylgymnemic acid (DAGA) which is 3-O-glucuronide of gymnemagenin (3, 16, 21, 22, 23, 28-hexahydroxy-olean-12-ene)2. The individual gymnemic acids (saponins) include gymnemic acids I-VII, gymnemosides A-F, gymnemasaponins

Extra Information -

G. sylvestre leaves contain triterpene saponins belonging to oleanane and dammarene classes. Oleanane saponins are gymnemic acids and gymnemasaponins, while dammarene saponins are gymnemasides. Besides this, other plant constituents are flavones, anthraquinones, hentri-acontane, pentatriacontane, α and β- chlorophylls, phytin, resins, d-quercitol, tartaric acid, formic acid, butyric acid, lupeol, β-amyrin related glycosides and stigmasterol. The plant extract also tests positive for alkaloids. Leaves of this species yield acidic glycosides and anthroquinones and their derivatives.

Gymnemic acids have antidiabetic, antisweetener and anti-inflammatory activities. The antidiabetic array of molecules has been identified as a group of closely related gymnemic acids after it was successfully isolated and purified from the leaves of Gymnema sylvestre. Later, the phytoconstituents of Gymnema sylvestre were isolated, and their chemistry and structures were studied and elucidated.

Use as herbal medicine

While it is still being studied, and the effects of the herb are not entirely known, the herb has been shown to reduce blood sugar levels when used for an extended period of time. Additionally, Gymnema reduces the taste of sugar when it is placed in the mouth, thus some use it to fight sugar cravings. From extract of the leaves were isolated glycosides known as Gymnemic acids, which exhibit anti-sweet activity.

This effect, however, is short-lived, lasting a mere fifteen minutes. Some postulate that the herb actually reduces cravings for sugar by blocking sugar receptors in the tongue, but no scientific studies have supported this hypothesis. It is currently being used in an all natural medication for diabetes with other ingredients such as cinnamon, chromium, zinc, biotin, banaba, huckleberry and bitter melon.

The active ingredient is thought to be gurmenic acid which has structure similar to saccharose. Extracts of Gymnema is not only claimed to curb sweet tooths but also for treatment of as varied problems as hyperglycemia, obesity, high cholesterol levels, anemia and digestion. According to the Sushruta of the Ayurveda it helps to treat Madhumeha ie glycosuria.

In 2005, a study made by King’s College, London, United Kingdom, showed that a water-soluble extract of Gymnema Sylvestre, caused reversible increases in intracellular calcium and insulin secretion in mouse and human β-cells when used at a concentration (0.125 mg/ml) without compromising cell viability. Hence forth these data suggest that extracts derived from Gymnema Sylvestre may be useful as therapeutic agents for the stimulation of insulin secretion in individuals with T2DM.

Mechanism of Action

Gymnemic acid formulations have also been found useful against obesity, according to recent reports. 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.

Gymnema 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. These compounds have also been found to increase fecal excretion of cholesterol, 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.

There are some possible mechanisms by which the leaves and especially Gymnemic acids from Gymnema 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-dependent pathways, an increase in phosphorylase activity, decrease in gluconeogenic enzymes and sorbitol dehydrogenase.
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 involve one or more mechanisms.

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.

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. 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.

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.

Alternative names

The plants also goes under many other names such as; Gurmari, Gurmarbooti, Gurmar, periploca of the woods and Meshasringa. The Hindi word Gur-mar (Madhunaashini in Sanskrit, Chakkarakolli in Tamil), literally means sugar destroyer. Meshasringa (Sanskrit) translates as "ram's horn", a name given to the plant from the shape of its fruits. Gymnema probably derives from the Latin word meaning naked and sylvestre means from the forest.

See also

References

The Useful Plants of India (UPI,1986); Publication and Information Directorate, CSIR New Delhi.

- Anturlikar, S.D. Gopumadhavan,S, Chauhan, School, Mitra, B.L., Mitra, S.K., Probe `V.34(3); P.211-221, 1995 (26 Ref.Eng).

-3. Mukherjee, P.K.; Rajesh Kumar, M; Saha, K; Giri, S.N.; Pal, M; Saha, B.P. Journal of Scientific and Industrial Research, V.55(3) Page 178-181, 1995 (Eng.14 Ref)

-4. Chakravarthi,D and Debnath, N.B. 1981 Isolation of Gymnemagenin, the Sapogenin from Gymnema Sylvestre R.Br. (Asclepiadaceae). Journal of the Institution of Chemists (India) 53, 155-158

-5. Glaser,D.;Hellekant, Gwalior., Brouwer, J.N., and Van der wel. Happy (1984) Effects of Gymnemic Acid and on sweet taste perception in primates . Chemical Sciences 8,367- 374.

-6. Gupta, S.S(1961) Inhibitory effect of Gymnema Sylvestre (Gurmar) on adrenaline induced Hyperglycemia in rats, Indian Journal of Medical Sciences 15, 883-887.

-7. Imoto, T.; Miyasaka, A., Ishima. R and Akasaka,K (1991) A novel peptide isolated from the leaves of Gymnema Sylvestre I. Charactorization and its supressive effect on the neural responses to sweet taste stimuli in the rat . Comparative Biochemistry and Physiology, 100A, 309-314.

-8. Kennady, L.M. (1989) Gymnemic Acids; specificity and comperitive inhibitation. Chemical Senses 14, 853-858

-9. Shanmugasundaram, K.R., Panneerselvam, C., Samudram, P and Shanmugasundaram E.R.B. (1983) Enzyme changes and glucose utilisation in diabestic rabbits; the effect of Gymnema Sylvestre, Journal of Agricultural and Food Chemistry 17, 704-708.

-10. Stocklin, W.(1969b) Chemistry and Physiological properties of Gymnemic acid, the anti-saccharine principle of the leaves of Gymnema Sylvestre, Journal of Ethnopharmacology 7, 205-234.

-11. Yoshikawa, K.,Amimoto, K, Arihara, School and Matsuura, K.(1989a) Structure Studies of new anti-sweet constituents from Gymnema Sylvestre. Trtrahedron Letters 30, 1103- 1106

-12. Yoshikawa,K, Amimoto,K, Arihara,S and Matsuura, K (1989b) Gymnemic Acid V,VI and VII from Gurmar, the leaves of Gymnema Sylvestre R.Br. Chemical and Pharmaceutical Bullitin 37, 852-854.

-13. Yoshikawa,K, Arihara,S, Matsuura, K and Miyase,T (1992a) Demmarane Saponins from Gymnema Sylvestre, Phytochemistry 31, 237-241

-14. Mukherjee,P.K., rajesh Kumar,M., Saha,K., Giri,S.N., Pal, M, Saha B.P. Preparation and evaluation of Tincture of Gymnema Sylvestre (Family- Asclepiadaceae) by Physico- Chemical, TLC and Spectroscopic characteristics. - Journal of Scientific and Industrial Research, V.55(3): P.178-181,1995 (Eng.14 Ref).

- 15. Anil, K.I., Nazaam,P.A., Joseph, L, Vijay Kumar, N.K. - Response of "Gurmar" for in vitro propagation. V.42(6); P 365-368, 1994 (Eng.Recd 1996,6 ref).

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