EPR and UV-Vis Spectroscopic Studies of the Influence of Ultraviolet Irradiation on Antioxidant Interactions of Nystatin

  The changes of the free radical scavenging activity of nystatin after UV-irradiation were examined. The kinetics of the interactions of nystatin with free radicals was tested. The model DPPH free radicals were used. Free radicals were tested by an X-band (9.3 GHz) electron paramagnetic resonance spectroscopy. The EPR spectra of DPPH and DPPH in contact with non-irradiated and UV-irradiated nystatin were measured. Nystatin quenched the EPR spectra of DPPH free radicals as the result of the antioxidative character of the samples. The antioxidative character of non-irradiated and UV-irradiated nystatin was confirmed by the UV-Vis studies. Free radical scavenging activity decreased after UV-irradiation of nystatin and the EPR spectra of DPPH free radicals lower decreased by contact with UV-irradiated nystatin. The quenching of UV-Vis spectra were lower for UV-irradiated nystatin than for than with non-irradiated drug. It was pointed out that nystatin should not be storage under ultraviolet irradiation, because of decrease its antioxidative interactions. This studies confirmed usefulness of EPR spectroscopy and UV-Vis spectrophotometry to determine of the antioxidant character of drugs. These spectroscopic methods may be used to find the optimal storage conditions of drugs.