Control tests were conducted by using pure compound 1 to
detect its inhibition at different concentration (Fig. 6). It was found
that when the concentration of compound 1 in the test sample
(solution of compound 1 illuminated at UV 254 nm at different
time) was the same as the control sample (solution of pure compound
1), both the test sample and the control sample showed
the same inhibition. So, we conclude that the a-glucosidase inhibitory
activity may be attributed to trans-isomer of N-p-coumaroyltyramine
and its cis-isomer (compound 4) has no a-glucosidase
inhibition, correspondingly.