[Absorption and fluorescence spectra of hypericin sodium salt in complexes with albumins]

The spectra of absorption and fluorescence of hypericin sodium salt (Na-Hy) in organic solvents and in complexes with human serum albumin, bovine serum albumin, and lipoproteins of low and high density have been studied. It was shown that, as the proton donor properties of the solvent enhance, the absorption and fluorescence maxima shift toward the blue region, and as the proton-accepting properties increase, the maxima shift toward the red region. The absorption spectra of complexes of Na-Hy with bovine serum albumin significantly differ from those of complexes of this ligand with human serum albumin, which is evidenced by a lesser width of absorption bands and a lower value of the Stokes shift. The positions of the absorption and fluorescence maxima and the value of the Stokes shift for the complex of Na-Hy with human serum albumin increases when D20 instead of common water is used as a solvent. It was concluded that H-bonds of hypericin play a significant role in the interaction with human serum albumin.