A study of fungicidal and anti-phenol oxidase activity of some α-amino phosphonate derivatives

Background: Developing new pesticides with multi-function may be a suitable strategy to save time and cost and reduce the emergence of resistant strains of pests and pathogens. The organophosphorus derivatives have not been widely used in agriculture as fungicides. In this work, a series of six alpha-amino phosphonate derivatives were prepared and tested for their fungicidal and anti-phenol oxidase activities. Results: The prepared compounds revealed a promising anti-fungal activity against Macrophomina phaseolina and Pythium aphanidermatum, especially M4, with MIC of 62 mg/L for M. phaseolina. M4 did not affect the fungus permeability rate of the cell membrane; however, it displayed a significant efficiency on mycelial soluble protein content. M4 and M3 with a hydroxyl group on the aniline moiety exhibited an observed anti-phenol oxidase activity. M4 inhibited the enzyme at 1 mg/mL. The DFT theoretical study revealed a significant correlation between the substituents of aniline moiety and the bioactivity of the studied compounds. The negative charge conspicuously influenced the anti-phenol oxidase activity. Conclusions: Our findings suggest the studied compounds as bases to design more effective alpha-amino phosphonate fungicides with additional anti-phenol oxidase activity. Graphic abstract