PHOTOCHEMICAL FORMATION OF SINGLET MOLECULAR-OXYGEN (O-1(2)) IN ILLUMINATED 6-METHYLCOUMARIN SOLUTIONS

Use of the fragrance 6-methylcoumarin (6-MC) in cosmetic products has declined significantly due to numerous reports of photoallergic contac t dermatitis associated with its use. We have determined that 6-MC und ergoes direct photolysis with an estimated half-life of 83 minutes whe n illuminated with midlatitude U.S., noon-centered, equinox sunlight a nd a quantum yield for photolysis at 313 nm of phi = 3x10(-3). The wor k presented here also provides evidence that singlet molecular oxygen (O-1(2)) is formed in illuminated solutions containing 6-MC. An estima ted value of phi = 0.01 is reported for the O-1(2) quantum yield at 31 3 nm. Formation of O-1(2) is significant because it is known to react with a variety of biomolecules and it is possible that O-1(2) formatio n is at least partially responsible for reports of 6-MC photoallergeni city and phototoxicity. (C) 1997 Academic Press.