Antidiabetic potentials of Syzygium guineense methanol leaf extract

Abstract

This study examines the effects of a methanol extract of Syzygium guineense leaves in streptozotocin (STZ) - induced diabetes, evaluates its effect on alpha glucosidase and 2, 2-diphenyl-1-picrylhydrazyl radical. Diabetes was induced in rats by a single intraperitoneal injection of streptozotocin (60 mg/kg). An oral glucose tolerance test was performed after diabetes induction and repeated after 14 days of treatment with the extract. The extract elicited antihyperglycemic action in diabetic rats evidenced by an improved oral glucose tolerance. A dose of 250 mg/kg of extract significantly (P<0.01, 0.001) enhanced glucose clearance at the end of treatment period and was comparable with metformin, the group also showed increase in hepatic glycogen content by 33.9% relative to the diabetic control. Serum biochemical analysis showed that the extract improved indices of renal and hepatic function by reduction in serum albumin, creatinine, liver enzymes, total and direct bilirubin. Similarly, the extract reduced serum cholesterol, triglycerides and high density lipoprotein (HDL) in a non-dose dependent manner; treatment with 250 mg/kg extract caused significant (P<0.05) reduction of HDL. Groups which received 250 and 500 mg/kg of extract showed reversal of glomerular damage compared with the diabetic untreated group. The extract also exhibited concentration-dependent antioxidant activity (EC50= 0.2 mg/ml) and statistically significant (P<0.01, 0.001) alpha glucosidase inhibitory effect (IC50= 6.15 mg/ml). These findings show the antidiabetic potential of S. guineense leaf extract, likely mediated through its ability to inhibit alpha glucosidase, scavenge free radicals and increase intrahepatic glucose uptake and storage.