Antihyperglycemic and antioxidant activities of Rhododendron schlippenbachii maxim. bark and its various fractions

2Korean Collection of Herbal Extracts, Inc., Kongju 314-701, Republic of Korea. Accepted 15 February, 2012 In this research, we evaluated the antidiabetic and antioxidant potential of 80% aqueous methanolic extract of the bark of Rhododendron schlippenbachii Maxim. along with its various fractions (n-hexane, dichloromethane, ethyl ethanoate, n-butyl alcohol and distilled water). The antihyperglycemic activity of all the fractions was investigated in vitro by α-glucosidase inhibition (using two types of enzyme sources) and in vivo in normal rats by evaluating the blood glucose lowering effect after maltose administration (1 g/kg bw). In addition, all these fractions were also evaluated by five diverse in vitro antioxidant assay systems, which include, ferrous ion chelating (FIC), 1,1diphenyl-2-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), 2,20-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) and lipid peroxidation inhibition (using rat liver) assays. We also examined the total phenolic and flavonoid contents for all of these fractions. In all, ethyl ethanoate and dichloromethane fractions exhibited potent antihyperglycemic and antioxidant effects in vitro and in vivo .