Cinnamic acid as one of the antidiabetic active principle(s) from the seeds of Syzygium alternifolium.

The Indian traditional system of medicine prescribed plant therapies for diseases including diabetes mellitus. One such plant is Syzygium alternifolium (SA). We reported earlier, that fraction C from aqueous extract of SA seeds showed good antihyperglycemic and antihyperlipidemic activities. In continuation to it, we have performed bioassay guided fractionation of fraction C and identified cinnamic acid as a component with antihyperglycemic activity. A detailed study was undertaken to elucidate its mode of antidiabetic action by giving fraction C (50 mg/kgb.w) orally, once a day for 30 days in STZ induced diabetic rats. The altered enzyme activities of carbohydrate metabolism in liver and kidney of diabetic rats were significantly (p<0.01) reverted to near normal levels by the administration of fraction C. Fraction C lowered blood glucose as expected, immediately following treatment, and led to glibenclamide-like modulatory effects on enzyme activities related to glucose homeostasis after 30 days treatment, indicating that cinnamic acid may prove useful in diabetes management.

Protective effect of Eugenia jambolana seed kernel on tissue antioxidants in streptozotocin-induced diabetic rats.

Oxidative stress plays an important role in chronic complications of diabetes. In the present study the antioxidant effect of oral administration of ethanolic extract of Eugenia jambolana seed kernel on tissue antioxidant enzymes and lipid peroxidation in liver and kidney of streptozotocin-induced diabetic rats was evaluated. Administration of seed kernel to diabetic rats significantly decreased the levels of blood glucose, glycosylated hemoglobin and increased body weight gain, plasma insulin and hemoglobin. The diabetic rats showed the low activities of superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione content in liver and kidney, which were restored to near normal levels by treatment with the seed kernel extract. The increased levels of lipid peroxidation and hydroperoxides in diabetic rats were reverted back to near normal levels after the treatment with seed kernel extract. Diabetic rats treated with seed kernel extract restored almost normal architecture of liver and kidney and were confirmed by histopathological examination. The present study reveals the efficacy of Eugenia jambolana seed kernel in the amelioration of diabetes, which may be attributed to its hypoglycemic property along with its antioxidant potential. The antioxidant effect of Eugenia jambolana seed kernel was also compared with glibenclamide, a standard hypoglycemic drug.