Antioxidant properties and in vitro α-amylase and α-glucosidase inhibitory properties of phenolics constituents from different varieties of Corchorus spp.

Objectives: This study investigated the phenolic constituents, antioxidant properties and effect of aqueous extracts from some Corchorus species (C. aestuans, C. bougoudo, C. capsularis, C. olitorius and C. urtifolicus) on alpha-amylase and alpha-glucosidase activities in vitro. Methods: Gas Chromatography with Flame Ionization Detector (GC-FID) was used to characterize the phenolic constituents. Aqueous extracts were prepared weight/volume (w/v) and their effects on alpha-amylase and alpha-glucosidase activities, Fe2+ induced lipid peroxidation, and 1,1-diphenyl-2 picrylhydrazyl (DPPH) radical scavenging properties were determined. Fe(2+ )chelating abilities and Ferric Reducing Antioxidant Power (FRAP) properties were also studied. The predominant phenolics detected by GCFID were kaempferol, rutin, apigenin, luteolin, caffeic acid and quercetin. The results showed that all the Corchorus species significantly (P < 0.05) inhibited alpha-amylase and alpha-glucosidase activities dose-dependently (0-8 mu g/ml). C. olitorius had the highest a-amylase inhibitory ability while C. bougoudo demonstrated the maximum a-glucosidase inhibition. However, all the Corchorus species inhibited alpha-glucosidase better than alpha-amylase and also exhibited antioxidant properties. Conclusions: The enzyme inhibitory and antioxidant properties exhibited by the Corchorus species could be attributed to their phenolic constituents and vitamin C content; a possible mechanism by which Corchorus species could elicit therapeutic effects on type 2 diabetes mellitus as obtained in folklore medicine.