Three new phenylpropanoyl amides from the leaves of Piper sarmentosum and their α-glucosidase inhibitory activities

Piper sarmentosum is pungent climber that is a widely used vegetable in Southeast Asia. In screening for alpha-glucosidase inhibitors from edible plants, an inhibitory activity in the leaf extract of P. sarmentosum was observed. Bioassay-guided fractionation resulted in the isolation of three new phenylpropanoyl amides, named chaplupyrrolidones A (1) and B (2) and deacetylsarmentamide B (7). Chaplupyrrolidones A and B contained a 5-oxygenated-Delta(3)-2-pyrrolidone moiety, which is the first report of their natural encounter. Of these all isolated compounds, 2 revealed most potent inhibition against alpha-glucosidase, which is 18-fold more active than its demethylated congener, 1. Kinetic evaluation of 2 indicated that it acts as a noncompetitive inhibitor. (C) 2013 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.