Salacia reticulata Wight ('Kotala himbutu' in Singhalese) and S. oblonga Wall ('Chundan' in Tamil, "ponkoraanti' in Malayalam) belonging to to the Hippocrateaceae, are large woody climbers distributed in Sri Lanka and Southern regions of India. The roots and stems of S. reliculata (SR) and roots of S. oblonga (SO) have been use in the treatment of rheumatism, gonorrhea and skin diseases, particularly in the initial stages of diabetes in Sri Lankan traditional medicine. In India, the plants have been prescribed as an anodyne, anti-inflammatory agent and liver tonic and also for wound healing and treatment of amenorrhea

Extracts from SR is consumed in Japan as a food supplement that prevents obesity and diabetes, because it suppresses postprandial hyperglycemia. Ayurveda advises that a person suffering from diabetes should drink water left overnight in a mug carved out of SR wood.

Japanese workers have isolated potent a-glucosidase inhibitors, Salacinol and Kotanalol, from both SR and SO as the antidiabetogenic principles.

These compounds are characterized by their unique spiro-like inner salt structure of 1-deoxy-4-thio-D-arabinofuranosyl sulfonium cation and 1-deoxysugar alcohol sulfate anion.

The ethyl acetate fraction of SO showed aldose reductase inhibitory activity while the polyphenolic constituents of SR exhibited both a-gluosidase and aldose reductase inhibitory activities. The phenolic compounds strongly scavenged DPPH radicals with an activity similar to those of known antioxidants, such as gallic acid, (+)-catechin and a-tocopherol. They also afforded protection against CCl4-induced liver injury, probably arising out of this antioxidant action.

a-Glucosidase inhibition: a-Glucosidase is an enzyme that decrease the absorption of carbohydrates from the intestine, resulting in a slower and lower rise in blood glucose throughout the day, especially right after meals. Before carbohydrates are absorbed from food, they must be broken down into smaller sugar particles like glucose by enzymes in the small intestine. By inhibiting this enzyme, carbohydrates are not broken down as efficiently and glucose absorption is delayed.

Extracts of SO and SR strongly inhibited the increase of serum glucose after administration of maltose or sucrose in rats. They further inhibited the rat intestinal maltase and sucrase in vivo with IC50 values of 42 and 66µg/ml, respectively. In comparing the activity with those of commercial glucosidase inhibitors, Acarbose and Voglibose, it was found that the maltase inhibiting activity of salacia extracts were slightly weaker than that of Acarbose and the sucrase inhibiting activity was comparable, while the isomaltase inhibiting activity was greater than that of Acarbose and nearly equal to that of Voglibose

Salacinol exhibited stronger inhibition of the increase in the serum glucose level in maltase- and sucrase-loaded rats than Acarbose.

A recent clinical study showed that 1000 mg of salacia extract reduced the plasma glucose and serum insulin levels by 23% and 29%, respectively in healthy, non-diabetic individuals, an effect similar to those obtained with modern day prescription drugs.

Aldose reductase catalyze the reduction of glucose to sorbitol.. Sorbitol does not diffuse readily across cell membranes and the intracellular accumulation of sorbitol has been implicated in the chronic complications of diabetes such as perepheral neuropathy, retinopathy and cataract. Mangiferin present in salacia has shown aldose reductase activity