Isolation and activity of N-p-coumaroyltyramine, an alpha-glucosidase inhibitor in welsh onion (Allium fistulosum)

A phenolic amide, N-p-coumaroyltyramine (1), was isolated as an alpha-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 x 10(-7) M. From a structure-activity relationship study of 1 and its related compounds, the occurrence of alpha-glucosidase inhibitory activity required a p-coumaramide structure, with an amide hydrogen and alkyl or aralkyl substituent on the amide part