Self-association of hypericin was investigated with absorption and fluorescence spectroscopy methods. Constants of hypericin association in a 50% aqueous solution of DMSO were determined in the function of temperature, and absorption spectra of the monomer and molecules participating in the complex were examined. Changes in enthalpy Delta H-0 and entropy Delta S-0 in the process of hypericin association accounted for -46 kJ mol (1) and -55 J mol (1) K (1), respectively. Molecular dynamics simulations methods were applied to determine conformations of the hypericin complex, and 'head-to-head' and 'head-to-tail' models of interaction were proposed. The 'head-to-head' conformation turned out to be the most stable one. (C) 2014 Elsevier B.V. All rights reserved.