Hyperforin is a phytochemical produced by some of the members of the plant genus Hypericum, notably Hypericum perforatum. Hyperforin has only been found in significant amounts in Hypericum perforatum (St. John's wort) with other related species such as Hypericum calycinum containing lower levels of the phytochemical. It is thought to be a reuptake inhibitor. It accumulates in oil glands, pistils, and fruits, probably as a plant defense against herbivory. Other Hypericum species contain low amounts of hyperforin. Hyperforin is believed to be the primary active constituent responsible for the antidepressant and anxiolytic properties of the extracts of St. John's wort. Hyperforin also induces cytochrome P450 enzymes CYP3A4 and CYP2C9 by binding to and activating the pregnane X receptor (PXR). The induction of CYP3A caused by hypericum perforatum seems to be heavily dependent on its hyperforin content.
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