Antidiabetic and hepatoprotective activity of the roots of Calanthe fimbriata Franch

Background: Calanthe fimbriata is a Tujia ethnic medicine with various medicinal value and it is traditionally used for the treatment of gastric ulcer, chronic hepatitis, pharyngitis, and so on. Objective: The current study was conducted to evaluate the antidiabetic activity of C. fimbriata methanol extract (CfME) in oral glucose tolerance test (OGTT) mice and in streptozotocin (STZ)-induced diabetic mice. Methods: Experimental diabetes was induced by intraperitoneal injection of STZ (60 mg/kg) for three consecutive days in mice. OGTT in mice and α-glucosidase inhibition assay were also adopted to investigate the activity and elucidate the mechanism of action. Gliclazide and metformin were used as standard drugs in OGTT mice and in STZ-induced diabetic mice experiments, respectively. Blood glucose, total cholesterol (TC), triglyceride (TG), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and hepatic glycogen were measured in plasma or in livers. Results: CfME exerted potently antihyperglycemic activity in OGTT mice and in STZ-induced diabetic mice and decreased ALT, AST and TG levels, improved hepatomegaly, and increased hepatic glycogen content, however, CfME failed to modify the normal blood glucose in normoglycemic mice and exhibited weakly inhibitory activity on intestinal α-glucosidase. Conclusion: The present study demonstrated that CfME exerted potently antidiabetic activity by restoring the liver function to increase the synthesis of hepatic glycogen and by improving insulin resistance of peripheral tissues to enhance the uptake and utilization of glucose.