Free radical damage to polyene antifungal antibiotics: changes in biological activity and thiobarbituric acid...

Polyene antifungal antibiotics contain thiobarbituric acid-reactive substances suggestive of the presence of peroxidic compounds. These peroxides appear to play no part in the drug's antifungal activities. The polyenes were relatively stable to further oxidation in air, but lost biological activity and native ultraviolet absorption upon irradiation with ultraviolet light or incubation with iron salts. No evidence was found for the participation of hydroxyl radicals in the observed damage to the polyene molecules. However, organic oxygen radicals were implicated and protection against ferrous salt dependent damage could be afforded by the addition of the antioxidant propylgallate.