A COMPARATIVE-STUDY OF THE VISIBLE-LIGHT PHOTOCHEMISTRY OF GILVOCARCIN-V AND GILVOCARCIN-M

Quantum yields for the formation of superoxide ions, O-2(-.), and sing let oxygen, O-1(2), were determined during the photolyses of gilvocarc in M (GM) in air-saturated dry dimethylsulfoxide (DMSO) and in 45:55 ( vol/vol) DMSO-water mixtures. The quantum yield for the photoreduction of methyl viologen by GM in nitrogen-saturated dry DMSO was also dete rmined. These values are not different, within experimental error, fro m those corresponding to gilvocarcin V (GV). Because GV is a strong ph otocytotoxic agent and GM is not, these results imply that Type I and Type II mechanisms are not important pathways in the cytotoxicity of G V.