Gymnema (gurmar)

Gymnema is a slender woody climber, much branched, up to several metres long; leaves are opposite, ovate to oblong with a rounded base, pointed tip and soft hairs above, veins prominent. Flowers are small and yellow, borne in umbellate cymes in the leaf axils; fruits are elongate follicles, seeds comose. Fresh leaves taste slightly sweet at first and then abolish the sensation of sweetness — the reason the plant is called 'gurmar' (sugar destroyer) in Hindi.

The species has a wide range in tropical and subtropical Asia, Africa and Oceania; according to Plants of the World Online (Kew), Gymnema sylvestre occurs in India, Sri Lanka, Southeast Asia (including Vietnam), southern China (Guangdong, Guangxi, Yunnan, Hainan), the Arabian Peninsula, Africa and Australia. In Vietnam it grows wild in midland and mountainous areas and is cultivated for its medicinal leaves and herbal tea.

The leaves contain gymnemic acids — the characteristic triterpenoid saponins — together with gymnemosides, other triterpenoids, flavonol glycosides (quercetin, kaempferol) and the polypeptide gurmarin. Gymnemic acids reduce intestinal glucose absorption and transiently suppress sweet taste on the tongue. Di Fabio et al. (2015) reviewed the chemical composition and traditional uses; Fabio et al. (2014) characterised the triterpenoids in depth.

Gymnema is a popular herb for blood-sugar support. A meta-analysis by Devangan et al. (2021) found improved glycaemic control in type 2 diabetes patients; Zamani et al. (2023) reported beneficial effects on blood lipids, glucose and blood pressure; Leach (2007) systematically reviewed clinical trials on glycaemia. Chewing the leaves or sugar-free gum is also used to curb sweet cravings; in Ayurveda the plant is called madhunashini ('sugar destroyer').

Leaf preparations are generally well tolerated at common doses, but may cause excessive hypoglycaemia when combined with diabetes medication — patients should monitor blood glucose and consult a doctor; pregnant and breastfeeding women should be cautious. The species has not been assessed by IUCN (Not Evaluated); rising medicinal demand calls for sustainable cultivation and harvesting.