Phenolic acids inhibit chloroplast mutagenesis in Euglena gracilis

The mutagenicity (bleaching activity) of of loxaoin (43 mu M) and acridine orange (AO) (13.5 mu M) in Euglena gracilis is inhibited by plant phenolics . Caffeic acid (CA), p-coumaric acid (PCA), ferulic acid (FA) and gentisic acid (GA) (25, 50, 100 and 250 mu M) exhibited a significant concentration- dependent inhibitory effect against ofloxacin-induced mutagenicity, which w as very effectively eliminated by the highest concentration of all four of those phenolic acids. The mutagenicity of AO was also significantly reduced in the presence of CA, PCA and FA (25, 50, 100 and 250 mu M) However, GA e xhibited no significant activity, even at the concentration of 250 mu M. Ba sed on the UV spectrophotometric measurements, we suggest that the antimuta genic effect of CA, PCA, FA and GA resulted from the scavenging of reactive oxygen species (ROS) produced by ofloxacin. On the other hand, the reducti on of AO-induced mutagenicity correlates with the binding capabilities of C A, PCA and FA, with the exception of GA. (C) 2000 Elsevier Science B.V. All rights reserved.