Determination of hypericin in plasma by high-performance liquid chromatography

Hypericin, a polycyclic dianthroquinone, is one of the characteristic ingredients of Hypericum perforatum extracts (St. John's wort, HP), which has antidepressant effects. Hypericin and the internal standard (I.S.), dansylamide, were extracted from plasma utilizing solid-phase extraction (SPE). Chromatography was performed using isocratic reversed-phase high-performance liquid chromatography (HPLC) with fluorescence end-point detection. The calibration curve was linear over the range 5-100 ng per ml of plasma. The sensitivity for hypericin was 75 pg on column. Mean inter- and intra-assay coefficients of variation (C.V.s) over the range of the standard curve were less than 10%. The absolute recovery for hypericin averaged 72.6%.