An investigation of phenolic compounds from plant sources as trypsin inhibitors

In the search of new trypsin inhibitors caffeic acid (1), cinnamic acid (2), gallic acid (3) and eugenol (4) from Cinnamomum zeylanicum, ferulic acid (5) from Impatiens bicolor, vanillin (6) from Melia azedarach and catechol (7) from Allium cepa were isolated through bioassay guided fractionation of the plant extracts. IC (50) values of the compounds 1, 2 and 5 were found to be 0.35 ± 0.02 mM, 0.96 ± 0.05 mM and 1.22 ± 0.06 mM, respectively. Lineweaver-Burk and Dixon plots and their secondary replots showed that 1 was non-competitive inhibitor of this enzyme with K(i) value 0.102 ± 0.006 mM.