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Inhibition of MAO and COMT by hypericum extracts and hypericin
1AnalytiCon Gesellschaft für Chemische Analytik und Consulting mbH, Berlin, Germany.
Abstract:
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, 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 inhibiting fraction contained hypericins as well as flavonols, the COMT-inhibition fraction being mainly flavonols and xanthones. The concentrations of inhibition shown might not be sufficient to explain the clinically proven antidepressive effect of hypericum particularly with regard to the inhibition of MAO activity.
Insights
This study investigated Hypericum extracts' effects on MAO and COMT enzymes. While MAO inhibition was observed, the concentrations may not fully explain Hypericum's antidepressant effects.
Area of Science:
- Pharmacology
- Natural Products Chemistry
Background:
- Hypericum (St. John's Wort) is used for depression.
- Its mechanism of action, particularly enzyme inhibition, requires further elucidation.
Purpose of the Study:
- To investigate the in vitro inhibitory effects of hypericin, total Hypericum extract, and its fractions on monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT).
Main Methods:
- Enzyme activity assays were performed using pork liver preparations.
- Various concentrations of hypericin, total Hypericum extract, and Hypericum fractions were tested.
Main Results:
- Hypericin, total Hypericum extract, and one fraction inhibited MAO activity at specific concentrations.
- COMT inhibition was not observed for hypericin, but was seen with the total extract and two fractions at 10(-4) mol/L.
- The MAO-inhibiting fraction contained hypericins and flavonols, while the COMT-inhibiting fraction was rich in flavonols and xanthones.
Conclusions:
- The observed in vitro enzyme inhibition by Hypericum components, particularly MAO inhibition, may not be sufficient to account for its clinical antidepressant efficacy.
- Further research is needed to fully understand the pharmacodynamic properties of Hypericum extracts.