SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS .17. BENZANTHRONE

The photochemistry of benzanthrone (7H-benz[de]-anthracene-7-one) has been studied using electron paramagnetic resonance (EPR) in conjunction with the spin trapping technique and the direct detection of singlet molecular oxygen luminescence. Irradiation (lambda(ex) = 394 nm) of benzanthrone (BA) in aerated ethanol, dimethylsulfoxide or benzene resulted in the generation of superoxide (O is approximately equal to 2) which was trapped by 5,5-dimethyl-1-pyrroline-N-oxide. The ethoxyl radical was also detected in ethanol. Photolysis of BA in deaerated basic ethanol led to the formation of BA anion radical, BA is approximately equal to, which was detected directly by ESR. This radical anion decayed back to BA with a unimolecular rate constant of 1.5 x 10(-3) s-1. The 1O2 quantum yields (lambda(ex) > 345 nm) for BA in ethanol, 90% ethanol and basic ethanol (0.1N NaOH) were 0.89, 0.88 and 0.28 respectively relative to Rose Bengal. The lower yield of 1O2 in basic ethanol may be attributable to the reaction of oxygen with BA is approximately equal to (which is generated in higher yield at alkaline pH) to give O2 is approximately equal to. These findings suggest that on exposure to light BA can generate active oxygen species which may be responsible for the photocontact dermatitis caused by BA in industrial workers exposed to this chemical.