St. John’s Wort – Botany, Therapeutic Uses, Constituents, Pharmaco, Adverse Effects

These data notwithstanding, it remains unclear whether these substances are transported into the brain in quantities sufficient to affect behavior. Studies with human liver fractions indicate that hyperforin is converted to 57 different metabolites. While metabolites are generally less likely to accumulate in the brain than parent compounds, the possibility remains that responses to St. John’s wort are mediated by some, as yet unidentified, chemical constituent or its metabolite. In either case, the lack of evidence for brain accumulation of hyperforin or hypericin, let alone for the flavonols, tannins, or any other chemical known to be present in St. John’s wort extract, leaves unanswered the question about which of these, or which combination of them, is responsible for its effects following oral administration. The absence of this information is a significant hindrance to characterizing a possible mechanism for the purported antidepressant effect of this extract.