Hypericin and Pseudohypericin. Purity Criteria and Quantitative Determination in Extracts of Saint John’s Wort (Hypericum perforatum)

Abstract

Hypericin and pseudohypericin in extracts of St. John’s Wort (Hypericum perforatum) are assayed using UV-Vis, measuring the absorbance at 588 nm of a methanolic solution of the compounds. The value of the absorption coefficient is difficult to define insofar as none of the routine purity criteria can be applied to these two compounds. Analysis of the entire UV-Vis spectrum from 220 to 740 nm would seem to be a reliable way of comparing different samples. A UV-Vis spectrum was recorded for each of the compounds using a Photodiode array detection system. A more accurate way of determining the levels of hypericin and pseudohypericin in extracts of St. John’s Wort using these reference spectra is described.