Phenylethyl cinnamides as potential alpha-glucosidase inhibitors from the roots of Solanum melongena.

Bioassay-guided fractionation against alpha-glucosidase resulted in isolation and identification of six phenolic compounds (1-6) from the 70% EtOH extract of the roots of Solanum melongena L. (Solanaceae). Of these, three phenylethyl cinnamides, N-trans-feruloyl tyramine (1), N-trans-p-coumaroyl tyramine (2) and N-cis-p-coumaroyl tyramine (3) possessed inhibitory activity against alpha-glucosidase with IC50 values of 500.6, 5.3 and 46.3 microM, respectively. Mechanism analysis revealed these phenylethyl cinnamides were non-competitive inhibitors. This is the first study of the alpha-glucosidase inhibitory activities of the roots of S. melongena, and this preliminary observation suggested potential medicinal use of this herb.