Pharmacodynamics:

General (See Studies listed in this section below):

It is not clear how Hypericum Perforatum works in its ability to treat some kinds of depression but there are several theories that are being investigated. One theory is that Hypericum Perforatum inhibits an enzyme called monoamine oxidase (MAO) and catechol methyl-transferase (COMT). Another is that it may raise the levels of a neurotransmitter called serotonin. Still another theory suggests that Hypericum lowers levels of the stress hormone cortisol or affects GABA receptors in the brain.

Along with the debate on it’s action is also the question of which constituent is responsible. Hypericin, pseudohypericin, amentoflavone, xanthones, and hyperforin are all being investigated as the possible active ingredient or combination of ingredients.

Studies:

Influence of hypericin, hypericum total extract, and hypericum fractions on the activity of MAO and COMT

"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." ²⁸

Inhibition of monoamine oxidase (MAO)

"The inhibition of monoamine oxidase (MAO) by six fractions from hypericum extract and three characteristic constituents (as p.r. substances) were analyzed in vitro and ex vivo to study the antidepressive mechanism of action. Rat brain homogenates were used as the in vitro model, while the ex vivo analysis was performed after intraperitoneal application of the test substances to albino rats. Massive inhibition of MAO-A could be shown with the total extract and all fractions only at the concentration of 10(-3) mol/L. At 10(-4) mol/L, one fraction rich in flavonoids showed an inhibition of 39%, and all other fractions demonstrated less than 25% inhibition. Using p.r. hypericin as well as in all ex vivo experiments, no relevant inhibiting effects could be shown. From the results it can be concluded that the clinically proven antidepressive effect of hypericum extract cannot be explained in terms of MAO inhibition." ²⁹

Inhibits uptake of serotonin and norepinephrine:

"Because known mechanisms of antidepressant activity include inhibition of serotonin and/or norepinephrine uptake, we investigated the effects of standardized extracts of Hypericum LI 160 on the transport of these monoamine neurotransmitters into astrocytes, cells which surround synaptic terminals and regulate neurotransmission by means of their uptake systems. We found that LI 160 inhibited both serotonin and norepinephrine uptake in a dose-dependent manner. The two monoamine transport systems were affected differently by LI 160: for serotonin, the main effect was a 50% decrease in the rate of maximal transport, whereas for norepinephrine, the main effect was a 4.5 fold reduction in the apparent affinity of norepinephrine for its uptake sites. Upon removal of LI 160, uptake was restored, thereby indicating that the inhibition was not due to a toxic effect of Hypericum on the cells. These findings suggest that the ability of LI 160 to inhibit serotonin and norepinephrine uptake may underlie the antidepressant activity of this Hypericum extract." ³⁰

Bookmark this page: