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Hydroalcoholic hypericum extract inhibits the synaptosomal uptake of serotonin, norepinephrine, and dopamine with about similar affinities and leads to a significant down-regulation of cortical beta-adrenoceptors and 5-HT2-receptors after subchronic treatment of rats. While neither hypericine nor kaempferol did show any reuptake inhibiting properties, hyperforin was identified as the unspecific reuptake inhibitor of hypericum extracts with half-maximal inhibitory concentrations for the three synaptosomal uptake systems mentioned above between 80 and 200 nmol/l. Moreover, a hyperforin-enriched (38%) CO2 extract also leads to a significant beta-receptor down-regulation after subchronic treatment. The data suggest hyperforin as the active principle of hypericum extracts in biochemical models of antidepressant activity.

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Hyperforin represents a major antidepressive constituent of St. John's wort (SJW) extract. It not only inhibits the neuronal uptake of serotonin, norepinephrine and dopamine like many other antidepressants, but also inhibits GABA and L-glutamate uptake. This broad-spectrum effect is obtained by an elevation of the intracellular Na+ concentration, probably due to activation of sodium conductive pathways not yet finally identified but most likely ionic channels. This makes hyperforin the first member of a new class of compounds with a preclinical antidepressant profile due to a completely novel mechanism of action.

No abstract