Measurement of hyperforin a constituent of St. John's wort in plasma by high-performance liquid chromatography.

Hyperforin is a constituent of Hypericum perforatum extracts (St. John's wort, H. perforatum), which have antidepressant action. Hyperforin was extracted from plasma utilising a solid-phase extraction procedure. Chromatography was performed by isocratic reversed-phase high-performance liquid chromatography with UV end-point detection. The calibration curve was linear over the range 0.15-3 microg per ml of plasma. The sensitivity for hyperforin was 4.5 ng on-column. Mean inter- and intra-assay relative standard deviations over the range of the standard curve were less than 5%. The absolute recovery for hyperforin averaged 97.8%.