Inhibition of MAO and COMT by hypericum extracts and hypericin
AU: Thiede-HM; Walper-A
AD: AnalytiCon Gesellschaft fur Chemische Analytik und Consulting mbH, Berlin, Germany.
SO: J-Geriatr-Psychiatry-Neurol. 1994 Oct; 7 Suppl 1: S54-6
Depression is associated with changes in levels of the neurotransmitters serotonin and norepinephrine, which are broken down by the enzymes mono-amino-oxidase (MAO) and catechol-O-methyl-transferase (COMT). It has been demonstrated that an inhibition of these enzymes has an antidepressant effect by lowering the breakdown, thus increasing the concentration of these neurotransmitters in the synapses between the nerve cells.
In 1978 Suzuki et al. demonstrated an irreversible MAO-inhibitory effect of hypericum extract; for a long time this was assumed to be the explanation for the antidepressant action of hypericum.
Later research has not been able to confirm this hypothesis; this study was done in order to further investigate the role of MAO and COMT in the antidepressant action of hypericum extracts.
The influence of hypericin, hypericum total extract, and hypericum fractions on the activity of MAO and COMT, prepared in vitro from pork liver, were investigated in several concentration steps.
An inhibition of MAO could be shown in the following concentrations (extract correlated to a mean molecular value of 500): hypericin to 10(-3) mol/L(= 500 microg/ml = unbelievably high in a human brain), hypericum total extract to 10(-4) mol/L, one extract fraction up to 10(-5). A COMT inhibition could not be shown for hypericin, with hypericum extract to 10(-4) mol/L and with two extract fractions also up to 10(-4) mol/L. The MAO-inhibition fraction contained hypericins as well as flavonols, the COMT-inhibition fraction being mainly flavonols and xanthones.
The concentrations of inhibition, particularly MAO activity, shown might not be sufficient to explain the clinically proven antidepressive effect of hypericum.
Copyright © 1996 by Harold H. Bloomfield, M.D. and Peter McWilliams