Pharmacognostical standardization and antidiabetic activity of Syzygium cumini (Linn.) barks (Myrtaceae) on streptozotocin-induced diabetic rats

Abstract

The objectives of the present study were phytochemical and pharmacological screening of bark of Syzygium cumini on streptozotocin (STZ)-induced diabetic Wistar albino rats. Dose selection was made on the basis of acute oral toxicity study (300-5,000 mg/kg b.w.) as per OECD guidelines. Rats were made diabetic by a single dose of STZ at 50 mg/kg b.w. intraperitoneally. The effect of Syzygium cumini extracts (500 mg/kg) on postprandial blood glucose level was determined in fasted diabetic and normal rats. Blood glucose levels were measured at 0, 30, and 90 min after the glucose administration in the OGTT study. The bark extracts were administered orally at the dose of 500 mg/kg for 21 days in the chronic study. Glibenclamide (2.5 mg/kg) was used as a standard drug for activity comparison. Statistical analyses were performed using one-way ANOVA followed by Bonferroni's multiple comparison tests. The phytochemical screening showed positive results for triterpenes/steroids, glycosides, carbohydrates, alkaloids, flavonoids, saponins, tannins and amino acids. Administration of Syzygium cumini extracts 30 min before oral glucose loading significantly suppressed (p<0.001) the rise in postprandial blood glucose levels in treated rats compared to control rats but less significant than glibenclamide. Daily, continuous oral treatment of STZ-induced diabetic with various extract of Syzygium cumini for 3 weeks resulted in significant reductions in fasting blood glucose levels compared with diabetic controls. The ethanol and aqueous extracts were most active. This study brings out the evidence regarding phytochemistry and pharmacological activities of Syzygium cumini.