α-Glucosidase and α-amylase inhibitory constituent of Carex baccans: Bio-assay guided isolation and quantification by validated RP-HPLC-DAD

Carex baccans is used extensively as food additive for its medicinal and nutritional properties. Its extract demonstrated significant inhibition of alpha-glucosidase and alpha-amylase with IC50 43.32 +/- 1.22 and 562.18 +/- 5.98 mu g/mL, respectively. A bio-assay guided approach was employed to identify the active constituent(s). Fractionation and purification of the extract led to the isolation of a potent inhibitor, (+)-alpha-viniferin, and of weak inhibitors smiglasides A and B. (+)-alpha-Viniferin was quantified in the extract and fractions using HPLC and the method was validated for linearity, limit of detection, limit of quantification, precision, and accuracy. The calibration curve showed good linearity (r(2) > 0.999) in the range of 7.813-250 mu g/mL. The identification of alpha-glucosidase and alpha-amylase inhibitory activity in C. baccans supports the possible use of the plant as functional food for the management of diabetes. The validated HPLC method for the study of plant extracts will be useful in future research. (C) 2012 Elsevier Ltd. All rights reserved.