The complex of hypericin with beta-lactoglobulin has antimicrobial activity with potential applications in dairy industry

Using a combination of molecular modeling and spectroscopic experiments, the naturally occurring, pharmacologically active hypericin compound is shown to form a stable complex with the dimeric form of beta-lactoglobulin (beta-LG). Binding is predicted to occur at the narrowest cleft found at the interface between monomers in the dimeric beta-LG. The complex is able to preserve the fluorescence and singlet oxygen photosensitizing properties of the dye. The equilibrium constant for hypericin binding has been determined as K-a = 1.40 +/- 0.07 mu M-1, equivalent to a dissociation constant, K-d = 0.71 +/- 0.03 mu M. The complex is active against Staphylococcus aureus bacteria. Overall, the results are encouraging for pursuing the potential application of the complex between hypericin and beta-LG as a nanodevice with bactericidal properties for disinfection.