Possible involvement of amine oxidase inhibition in the sympathetic activation induced by khat (Catha edulis) chewing in humans.

The possibility that phenylalkylamines (cathinone and cathine) of khat, like amphetamines, are amine oxidase inhibitors with clinical significance is evaluated. Results show that khat chewing induces a significant increase in blood pressure, body temperature and urinary catecholamines in khat naive subjects. On the other hand, in habitual consumers a significant enhancement only of blood pressure is observed. Urinary concentrations of vanilmandelic acid show an inhibitory trend in both groups of subjects. This has been related to a decrease in catecholamine deamination. In fact, oxidative deamination of benzylamine catalyzed by beef plasma amine oxidase is non-competitively inhibited in vitro by cathinone (Ki = 0.05 mM) and cathine (Ki = 10 mM) as well as by amphetamine (Ki = 7.9 mM).