Abstract
Monoamine oxidase (MAO) plays an important role in the inactivation of monoamines in body, such as serotonin, adrenaline and noradrenaline.
Many hydrazines and hydrazides that had been synthesized for antituberculous activity in 1952 were re-examined as possible MAO inhibitors by Zeller and his collaborators (1, 2). They reported that 1-isonicotinyl-2-isopropyl hydrazine (IIH, Marsilid, Iproniazid) was a potent, relatively selective and irreversible inhibitor of MAO, whereas its close analogue isonicotinic acid hydrazide (INH, Rimifon, Isoniazid) was not, but inhibited diamine oxidase (DAO) selectively. This difference permitted the investigation of the physiological function of these enzymes (3, 4). By their extensive studies on MAO inhibitors (5), they found that alkyl hydrazines and benzyl hydrazine displayed more potent inhibition on MAO. Recently, Horita (6) reported that β-phenylisopropyl hydrazine (PIH) caused a potent and prolonged inhibition on MAO.
In the present paper, the inhibitory effects of INH derivatives and hydrayine derivatives on MAO and DAO were compared and found that p-methylphenyl hydrazine (MPH) showed a selective and more potent inhibition on MAO.
