ABSTRACT
The number and variety of phototoxic compounds are large. Furthermore, for most phototoxic xenobiotics, a correlation between structure and photoreactivity is not easily found. It is obvious that, in general, a relationship must exist between photochemical behavior and phototoxicity. This chapter discusses the role of type II reactions involving the photoactivated drug in its triplet state transferring energy to molecular oxygen to generate singlet oxygen, superoxide anion, or hydroxyl radical, causing oxidation or peroxidation of membrane lipids. In the last 10 years, we have examined the photolysis of diuretic drugs under mild conditions, similar to those encountered in biological systems — namely, neutral, oxygenated media or under argon atmosphere and irradiation carried out with visible light. These investigations were performed keeping two main goals in mind: (1) to establish the nature of the different photoproducts, and (2) to obtain evidence of the role of oxygen in these photoprocesses and in the
in vitro
phototoxicity.
