The extra-weak chemiluminescence generated during oxidation of some tetracycline antibiotics. II. Peroxidation.

This study was undertaken to establish the mechanism of chemiluminescence during the oxidation reaction of tetracycline antibiotics in the presence of molecular oxygen and H2O2. The spectral distribution of chemiluminescence and fluorescence and the quantum yields of chemiluminescence were measured. The chemiluminescence spectrum measured with cut-off filters revealed one broad blue-green band and bands with maxima at 580, 640 and 700 nm. The bands at 580, 640 and 700 nm were similar to those observed for singlet molecular oxygen. The effect of superoxide radical, hydroxyl radical inhibitors, singlet oxygen quenchers and D2O as solvent on the light emission was also studied. The formation of singlet oxygen during the oxidation of the investigated tetracyclines was also checked using the spectrophotometric method based on the bleaching of p-nitrosodimethylaniline. A mechanism for the reactions generating electronically excited compounds is proposed.