Determination of hypericin and pseudohypericin from Hypericum perforatum in rat brain after oral administration

Abstract

The popularity of St. John’s Wort (SJW) extracts for treating mild to moderate depression has increased over the last decades and great effort has been devoted to identify the active principle of SJW extract. Previous investigations suggest the contribution of at least three classes of compounds, the phloroglucinols, the quercetin flavonoids, and the phenanthroperylenequinones, to the clinical efficiency of SJW extracts. Up to now, a plausible molecular mechanism of action has been described only for the phloroglucinols. For the flavonoids and the phenanthroperylenequinones different targets were proposed on the basis of pharmacological studies. The vast majority of these targets are located in the CNS and therefore increasing interest in the question of the CNS availability of these substances arose. Recently, the ability of phloroglucinols and flavonoids to penetrate the blood brain barrier could be demonstrated. For the phenanthroperylenequinones an examination of CNS bioavailability is still missing.

The aim of this work is to close this gap by developing and validating a HPLC method with electrochemical detection for the quantification of the phenanthroperylenequinones in brain tissue of rodents after oral application of SJW extract or pure hypericin. In our study, the phenanthroperylenequinone content in the CNS tissue was below the lower limit of detection of the analytical method and was thus lower than 16 pmol/g brain for hypericin and lower than 52 pmol/g brain for pseudohypericin after oral administration of 1600 mg/kg SJW extract or pure hypericin (5 mg/kg).