In vitro studies of the dual properties of Allopurinol anti- and photo-oxidants Mechanisms

the objective of this study was to investigate the ability of allopurinol (1) to inhibit free radical or reactive oxygen species (.oh, 1o2, h2o2) as well as the study of its photochemical activity. we investigated the ability of 1 to scavenge oxygen metabolites generated by cell-free systems using luminol enhanced-chemiluminescence and electronic absorption spectra as monitors. both absorbance and fluorescence scans reveal that 1 is able to react with equimolar quantities of h2o2. in the presence of 1 a dose-dependent inhibition period was observed in this system as assayed by isoluminol-enhanced chemiluminescence (ilcl) in the presence of horseradish peroxidase (hrp), as well as by luminol-enhanced chemiluminescence (lcl) in the presence of h2o2 or ferrous ion. on the other hand, 1 did not show an efficient scavenging activity of galvanoxyl radical in ethanolic solutions. furthermore, in a separate experiment, it was not observed trapping of singlet oxygen (1o2) generated by rose bengal, in the presence of 1. the activity of 1 was compared with that of vitamins e and c. in vitro experiments of photohemolysis in presence of 1 and cinoxacin, a phototoxic antibacterial quinolone, the photohemolytic effect of cinoxacin was diminished. allopurinol alone did not show any phototoxic effect under irradiation with uv-a or visible light but was photo-unstable and phototoxic in vitro with uv-b light.