STUDIES OF THE SULFONATION OF HYPOCRELLIN-A AND THE PHOTODYNAMIC ACTIONS OF THE PRODUCT

Hypocrellin A (HA), a perylenoquinone derivative, is an efficient phototherapeutic agent. The reaction of HA with Na2SO3 in alkaline solution under reflux led to the formation of the sodium salt of 14-dehydroxy-15-deacetyl-hypocrellin A-13-sulfonate (13-SO3Na-DDHA). ESR studies in combination with chemical methods showed that 13-SO3Na-DDHA was an active photosensitizer. An ESR spectrum, assigned to the semiquinone radical anion of 13-SO3Na-DDHA was generated by illumination of a DMF buffer (1:1 by volume) solution of 13-SO3Na-DDHA in the presence of a series of reductive biomaterials. Using 13-SO3Na-DDHA as photosensitizer and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap, the ESR spectra of DMPO/SO3- radical adduct, ascorbyl radical and DMPO/O2.- radical adduct were obtained. Singlet oxygen formed from 13-SO3Na-DDHA photosensitization was detected by means of the 13-SO3Na-DDHA photosensitized oxidation of anthracene and ESR spectroscopy. It was therefore concluded that the photodynamic actions of 13-SO3Na-DDHA proceeded via both Type 1 and Type 2 reactions.