Phenolics Constituents and In‐vitro α‐amylase, α‐glucosidase and Ecto‐ 5'nucleotidase Inhibitory Properties of Selected Solanum spp

Abstract

Control of postprandial plasma glucose levels is critical in the early management of diabetes mellitus,and in reducing chronic vascular complications such as obesity.This study investigate the phenolics, antioxidant properties, and effect of extracts from selected Solanum spp (S. melongena, S. macrocarpon, S.anguivi, S. aethiopicum, S. kumba and S.gilo) on α‐amylase, α‐glucosidase and 5'nucleotidase related to diabetes in‐vitro. HPLC‐DAD was used to characterize the phenolic constituents. Aqueous extracts were prepared and its effect on α‐amylase, α‐glucosidase, and ecto‐5'nucleotidase activities as well as antioxidant [Fe2+ induced lipid peroxidation, hydroxyl radical, 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging, Fe2+ chelating ability and ferric reducing antioxidant properties were determined. The predominant phenolics detected were quercetin, quercitrin, kaempferol, chlorogenic acid, caffeic acid and rutin. The results showed that all the Solanum species significantly (P<0.05) inhibited α‐amylase, α‐glucosidase, in a concentration dependent manner (0‐2µg/ml) with S.aethiopicum having the highest α‐glucosidase inhibitory ability while S.melongena had the highest α‐amylase inhibitory activity. Extract from these species S.melongena, S.macrocarpon, S.anguivi,S. kumba) had inhibitory effect on ecto‐5'nucleotidase activity while others had stimulatory effect. The enzyme inhibitory and antioxidant properties exhibited these species could be attributed to their individual /synergistic phenolic constituents and Vitamin C content, thus explaining possible biochemical rationale behind their use in the management of diabetes.