Isolation and Activity of<i>N</i>-<i>p</i>-Coumaroyltyramine, an<i>α</i>-Glucosidase Inhibitor in Welsh Onion (<i>Allium fistulosum</i>)

Abstract

A phenolic amide, N-p-coumaroyltyramine (1), was isolated as an α-glucosidase inhibitor from methanol extracts of Welsh onion (Allium fistulosum). The inhibitory activity of 1 against a yeast enzyme was as high as Ki 8.4 × 10−7 m. From a structure-activity relationship study of 1 and its related compounds, the occurrence of α-glucosidase inhibitory activity required a p-coumaramide structure, with an amide hydrogen and alkyl or aralkyl substituent on the amide part.