Evaluation of synaptosomal uptake inhibition of most relevant constituents of St. John's wort.

In our previous investigations, we could demonstrate that extract preparations of Hypericum perforatum (St. John's wort, SJW) inhibit the uptake of several neurotransmitters (serotonin, norepinephrine, dopamine, GABA, L-glutamate) in synaptosomal preparations of rodent brain. Hyperforin, the lipophilic constituent, was identified as the main component responsible for these effects. The properties seen for hyperforin in these and other pharmacological models present a plausible and logical explanation for the well documented antidepressive effects of SJW extract preparations in clinical studies. However, evidence for other active principles in SJW extract have been reported (See also communications by Misane & Ogren and Philippu in this issue). Accordingly, we tested various SJW extract preparations and all relevant constituents as possible inhibitors of synaptosomal uptake of neurotransmitters. Two further components were found to be active in those models. Adhyperforin, like hyperforin, showed a strong inhibiting profile in all uptake systems investigated. Moreover, we could observe a weak to moderate inhibiting profile for the oligomeric procyanidins fraction (OPC). Further investigations would have to clarify any possible contribution of these two constituents to the antidepressive effects of SJW extract seen in animal experiments and clinical trials.