OBJECTIVETo explore and identify the most potent antihyperglycemic fraction from the ethanol extract of Rhododendron arboreum (R. arboreum) flowers.

METHODSNormal and streptozotocin induced diabetic rats were treated with all four fractions of R. arboreum flowers for short term and with fraction 3 for long term study. On completion of the treatment, a range of indicators were tested including fasting blood glucose, plasma protein, haemoglobin A1C, insulin secretion, body weight, blood lipid profile and carbohydrate metabolism regulating enzymes of liver.

RESULTSIn short term study, the fraction 3 (Active fraction) produced a significant (P<0.000 1) reduction (73.6%) in blood glucose level at a dose of 200 mg/kg after the treatment in the diabetic rats. Administration of active fraction (200 and 400 mg/kg) once daily for 30 d in streptozotocin diabetic rats resulted in a significant (P<0.001 to P<0.000 1) fall in blood glucose level, hemoglobin A1C, serum urea and creatinine with significant but a increase in insulin level similar to standard drug glybenclamide. Further, the active fraction showed antihyperlipidemic activity as evidenced by significant (P<0.001 to P<0.000 1) decreases in serum serum total cholesterol, triglycerides, low density lipoprotein cholesterol and very low density cholesterol levels coupled together with elevation of high density lipoprotein cholesterol in the diabetic rats.

CONCLUSIONSThe active fraction of R. arboreum flowers decreases streptozotocin induced hyperglycemia by promoting insulin secretion and glycolysis and by decreasing gluconeogenesis.

Animals ; Blood Glucose ; drug effects ; Carbohydrate Metabolism ; drug effects ; Diabetes Mellitus, Experimental ; drug therapy ; metabolism ; Disease Models, Animal ; Flowers ; chemistry ; Hypoglycemic Agents ; chemistry ; pharmacology ; Hypolipidemic Agents ; chemistry ; pharmacology ; Lipids ; blood ; Male ; Phytochemicals ; chemistry ; Plant Extracts ; chemistry ; pharmacology ; Rats ; Rhododendron ; chemistry ; Toxicity Tests, Acute