THE PHOTOCHEMISTRY OF NYSTATIN IN VARIOUS SOLVENTS .2. A SPECTROFLUOROMETRIC STUDY

The influence of solvents (water, acetonitrile, dimethylsulfoxide, dim ethylformamide, methanol, dichlormethane, tehrahydrofuran, chloroform, dioxane and carbon tetrachloride) on the fluorescence spctra, quantum yield and lifetime of nystatin was studied. The fluorescence decay is two-fold exponential suggesting the presence of two fluorophors; thei r weight depends on the nature of the solvents which may perturb the s tructure of the tetraenic chromophore by the distinct action on the tw o neighbouring flexibility sites: the simple bond C-28 - C-29 and the asymmetrical carbon atom C-19. UV irradiation determines the decrease of fluorescence intensity and changes in C-19 the absorption spectrum; these effects are assigned to trans - cis isomerization of tetraenic chain. The process is catalyzed by the presence of carbonyl group.