Insulin-secretagogue, antihyperlipidemic and other protective effects of gallic acid isolated from Terminalia bellerica Roxb. in streptozotocin-induced diabetic rats

Diabetes mellitus causes derangement of carbohydrate, protein and lipid metabolism which eventually leads to a number of secondary complications. Terminalia bellerica is widely used in Indian medicine to treat various diseases including diabetes. The present study was carried out to isolate and identify the putative antidiabetic compound from the fruit rind of T. bellerica and assess its chemico-biological interaction in experimental diabetic rat models. Bioassay guided fractionation was followed to isolate the active compound, structure was elucidated using H-1 and C-13 NMR, IR, UV and mass spectrometry and the compound was identified as gallic acid (GA). GA isolated from T. bellerica and synthetic GA was administered to streptozotocin (STZ)-induced diabetic male Wistar rats at different doses for 28 days. Plasma glucose level was significantly (p < 0.05) reduced in a dose-dependent manner when compared to the control. Histopathological examination of the pancreatic sections showed regeneration of beta-cells of islets of GA-treated rats when compared to untreated diabetic rats. In addition, oral administration of GA (20 mg/kg bw) significantly decreased serum total cholesterol, triglyceride, LDL-cholesterol, urea, uric acid, creatinine and at the same time markedly increased plasma insulin, C-peptide and glucose tolerance level. Also GA restored the total protein, albumin and body weight of diabetic rats to near normal. Thus our findings indicate that gallic acid present in fruit rind of T. bellerica is the active principle responsible for the regeneration of beta-cells and normalizing all the biochemical parameters related to the patho-biochemistry of diabetes mellitus and hence it could be used as a potent antidiabetic agent. (C) 2010 Elsevier Ireland Ltd. All rights reserved.