Hypoglycemic activity of constituents from Astianthus viminalis in normal and streptozotocin-induced diabetic mice.

Astianthus viminalis has been used as a medicinal plant for a long time owing to its many physiological actions such as anti-inflammatory and antidiabetic activities. A new tetracyclic triterpenoid 3beta,19alpha-dihydroxyurs-12,20(21)-diene-28-oic acid (1), known constituents oleanolic acid (2) and ursolic acid (3), and the coumarins 7,8-dimethoxycoumarin (4) and 7-methoxycoumarin (5) were isolated from the chloroform extract of the leaves of A. viminalis. The structure and relative configurations of 1 were determined by spectroscopic methods (1H- and 13C-NMR, IR, and MS) and 2D-NMR experiments. The hypoglycemic ingredients of A. viminalis were characterized as compounds 1-3. The hypoglycemic effect of the isolated natural product 1 was investigated in normoglycemic and streptozotocin (STZ)-induced diabetic mice. All effects were compared with those of tolbutamide. Triterpenoid 1 showed potent hypoglycemic and hypolipidemic effects in the STZ-induced diabetic mice. Continuous administration of 1 (30 mg/kg, orally) led to significant decrease in the level of glucose, triglycerides, total cholesterol, LDL, and VLDL in the diabetic mice, whereas the level of HDL did not alter significantly in any of the groups studied.