Oxidative photo-catalyzed degradation of a new biological fungicide, phenazine-1-carboxylic acid

Phenazine-1-carboxylic acid (PCA) is a secondary metabolite produced primarily by Pseudomonas spp. and has been used as a potential fungicide towards many soil-borne fungal phytopathogens due to its broad-spectrum antibiotic activity. The present study aimed to investigate the photo stability of PCA to different types of light sources and degradation behavior in different environments, including at pH values and oxidants existing in the solution. Results showed that PCA was found to be very stable in a dark environment. However, UV radiation and visible light could induce its degradation and the photochemical reaction rate increased in the different solutions with the following order: methanol > ethyl acetate > acetone> phosphate buffer solution (pH 6.8). Analysis of pH profile showed that PCA becomes quite unstable towards decreasing the pH value of the environment. During the photo degradation of PCA, singlet oxygen was quenched by the addition of sodium azide and no measurable super oxide anion was produced, which suggests that the photo degradation of PCA was photo sensitized oxidation by the type II pathway. Moreover, oxygen and hydrogen peroxide could also enhance the photo degradation of PCA in an aqueous solution. The data obtained from this study would be beneficial for the future application of PCA in agricultural production processes.