Propargylamine was reported many years ago to be a mechanism-based inhibitor of bovine plasma amine oxidase (BPAO), though the potency was modest and allylamine was a substrate. Herein, selected 3-substituted propargylamines and allylamines were found to be potent time-dependent inactivators of BPAO, exhibiting IC50 values of 2-13 muM at 30 degreesC, making them the most potent BPAO inhibitors reported to date. The most potent compound, trans-3-chloroallylamine, was previously found not to inhibit the flavin-dependent monoamine oxidase (the cis isomer did), and thus appears to be a highly selective inhibitor. (C) 2003 Elsevier Science (USA). All rights reserved.