Absorbance data of hypericin and pseudohypericin used as reference compounds for medicinal plant analysis

The evaluation of the absorbance data of hypericin and pseudohypericin reve aled the molar/specific coefficients of absorbance in methanol-pyridine (99 .1, v/v) at the maximum of the longest wavelength to be 51936/1030 and 4348 6/836, respectively. The absorbance data of hypericin were also determined in methanol. They were not significantly different from those in the presen ce of pyridine. The decrease of the coefficients by water addition was foun d to be the same for hypericin and pseudohypericin. It was concluded that h ypericin and pseudohypericin reveal the same homoassociation behavior.