Antihyperglycemic and antihyperlipidemic activity of ethyl acetate fraction of Rhododendron arboreum Smith flowers in streptozotocin induced diabetic rats and its role in regulating carbohydrate metabolism

Objective:To explore and identify the most potent antihyperglycemic fraction from the ethanol extract of Rhododendron arboreum(R.arboreum)flowers.Methods:Normal 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.Results:In short term study,the fraction 3(Active fraction)produced a significant(P<0.0001)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<0.0001)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<0.0001)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.Conclusions:The active fraction of R.arboreum flowers decreases streptozotocin induced hyperglycemia by promoting insulin secretion and glycolysis and by decreasing gluconeogenesis.