Photodynamic action of amino substituted hypocrellins: EPR studies on the photogenerations of active oxygen and free radical species

A novel method has been employed to prepare 2-butylamino-2-demethoxy hypocr ellin A (BADMHA) and 3-butylamino-2-demethoxy hypocrellin B (BADMHB). Both compounds exhibit stronger absorption at the phototherapeutic window (600-9 00: nm). The spin trapping and spin counteraction studies have shown that t hey are both efficient generators of the active oxygen (O-1(2), O-2(.-)) in the aerobic condition. Under the anaerobic condition they generate non-oxy gen free radical (semiquinone radical anion), and the active oxygen mechani sm of photosensitization can be converted into cion-oxygen free radical mec hanism with the depletion of oxygen. The quantum yields of O-1(2) generatio n of BADMHA and BADMHB are 0.46 and 0.44, respectively. Both are lower than those of their parent compounds HA and HE. But the productions of superoxi de anion are enhanced significantly compared with HA and HE, indicating the y are both favorable Type I phototherapeutic agents. (C) 2000 Elsevier Scie nce S.A. All rights reserved.