INHIBITION OF LIVER-DERIVED MONOAMINE OXIDASE BY SEVERAL ISOPROPYL HYDRAZIDES

Six aromatic hydrazide derivatives were examined for their ability to inhibit enzymatic oxidation of tyramine in vitro utilizing the Warburg technique. Two compounds, 1‐p‐chloro‐ and 1‐p‐hydroxybenzoyl‐2‐isopropyl hydrazide, were included in this study in order to compare their in vitro activities with their reported MAO inhibiting actions in vivo. Four of the acyl isopropyl hydrazines examined were recently synthesized substances whose biologically‐relevant activities had not been previously investigated. Iproniazid served as a reference standard against which the other hydrazides were compared. Dose‐dependent inhibitory effects were demonstrated for all compounds and activities were expressed in terms of interpolated ID50′s, micromolar concentrations of drugs required to reduce the rate of oxygen uptake to 50 percent of the control rate. None of the substances examined exceeded iproniazid in potency although the 1‐p‐chlorobenzoyl analog proved to be equivalent to the standard in activity. Copyright © 1968 Wiley‐Liss, Inc., A Wiley Company