Evaluation of antidiabetic potential of Syzygium kanarense (Talbot) Raizada in streptozotocin- nicotinamide induced diabetic rats.

Worldwide diabetes is the major killer disease and the antidiabetic drugs which are in use cause many side effects. Traditionally, some of the Syzygium spp. are in use for treating diabetes, and many species are being assessed for their antidiabetic property. This study is to assess the antidiabetic effectiveness of the bark of Syzygium kanarense (Talbot) Raizada. The antidiabetic efficacy of methanol and water extracts of the leaf (SKLM, SKLW) and the bark (SKBM, SKBW) were evaluated in vitro by the alpha-glucosidase- and alpha-amylase-inhibitory assays. The in vivo antidiabetic activity of the bark was assessed by oral glucose tolerance test (OGTT) and streptozotocin- nicotinamide (STZ-NA)-induced non-obese type 2 diabetic rat model. The serum biochemical parameters and histopathology of the pancreas, liver and kidney were evaluated after 21 days of treatment. The total phenolics and flavonoids were quantified in all the extracts. The antioxidant activity was assessed using the DPPH assay. Administration of SKBM and SKBW to STZ-NA-induced diabetic rats at 300 mg/kg and 600 mg/kg orally for 21 days exhibited statistically significant (P < 0.001) and dose-related drop in blood sugar levels, serum lipid and hepatorenal parameters. The extract-treated rats showed rejuvenated islets and increased beta-cell density in the pancreas, improved liver architecture and glomerular regeneration without fat deposition. Bark extracts showed the strongest alpha –glucosidase- and alpha –amylase-inhibitory activity in contrast to the leaf extracts. Antioxidants, phytoconstituents and antidiabetic action, as well as protection against free radical damage, were proved to be significantly correlated.