Monoamine oxidase inhibitory activity in tobacco particulate matter: Are harman and norharman the only physiologically relevant inhibitors?

These results show that harman and norharman provide only a moderate contribution to the total monoamine oxidase-A inhibitory activity of tobacco smoke, perhaps under 10%. This suggests that other inhibitors (either known or unknown) may be more significant contributors to total inhibitory activity than has yet been established, and deserve closer examination.