Spectrofluorimetric determination of hypericin in drugs and vegetable raw materials

Abstract

For use as a standard sample, hypericin was isolated from the “Diahyperon” tincture. The chromatographic purity of the hypericin sample was confirmed by high-performance liquid chromatography/mass spectrometry. Hypericin is represented by a single chromatographic peak with a retention time of 23.10 min, which has a characteristic signal of the molecular ion [M - H⁺] ^- with m/z 504.05 in the mass spectrum. In addition to the band characteristic of hypericin at 550 and 590 nm, the electronic absorption spectra of the “Diahyperon” tincture and a methanolic extract of Hyperici herba (Hypericum perforatum) show an absorption band at 665 nm due to the presence of chlorophyll. It was shown that upon excitation of hypericin (λ_ex = 470 nm), the emission spectrum of the “Diahyperon” tincture contains bands characteristic of hypericin at 593 and 640 nm. In addition to the hypericin emission bands, the emission spectrum of the methanolic extract of Hyperici herba demonstartes a low intensity chlorophyll emission band at 670 nm. It was found that the spectrophotometric and spectrofluorimetric determination of hypericin in “Diahyperon” tincture and in Hyperici herba gives convergent results, which are consistent with the standardized values of the hypericin content in the studied samples.