Photoprocesses in photosensitizing drugs containing a benzophenone-like chromophore

Ketoprofen, suprofen and tiaprofenic acid are present almost exclusively as the carboxylate anions in aq. medium at neutral pH. The main photoreaction is decarboxylation leading to the corresponding Et derivs. and, in the presence of oxygen, to oxidn. products. Despite structural similarity of the photoproducts, important peculiarities were found in the photodegrdn. mechanisms. This paper illustrates the relationship between the excited state character and the photoreactivity pathways. The role of the environment is also discussed in the light of the results obtained in drug-β-cyclodextrin inclusion complexes. The photodegrdn. of ketoprofen, suprofen and tiaprofenic acid (carboxylate forms) was investigated in aq. medium and in the β-cyclodextrin cavity and the photochem. intermediates were characterized by time resolved emission and absorption studies in the picosecond, nanosecond, and microsecond time domains. Quantum mech. calcns. contributed to assign the electronic nature of the lowest energy electronic states. The main results of these studies are presented and the structural/environmental factors detg. the features of the photoreactivity of these compds. are highlighted.