Genotoxicity of pure compounds and commercial formulations of the maize herbicides mesotrione and s-metolachlor in Vicia faba L.

Abstract

Herbicides containing the active components mesotrione and S-metolachlor persist in the environment and adversely affect non-target organisms. Therefore, it was of interest to examine the toxicological risk associated with these compounds. This study aimed to investigate the toxic effects of the active pure compounds mesotrione and S-metolachlor and their respective commercial formulations as evidenced by MN bioassays utilizing Vicia faba L. (broad bean) as a model. The experiments followed the 48-hr protocol of ISO 29200. Dilutions of the active components and their commercial formulations, ranging from 1.56 to 50 mg/L, were tested. Hoagland's solution was used as a negative control, and maleic hydrazide as a positive control. A decrease in mitotic index (MI) was observed with the pure compounds, where mesotrione significantly reduced the frequency of cell division at concentrations >12.5 mg/L, and S-metolachlor initiated a significant fall at only the highest concentration (50 mg/L). In addition, the MN frequency was markedly increased at treatments of 3.125 mg/L mesotrione and 6.25 to 25 mg/L S-metolachlor. However, herbicide treatments with the commercial formulation containing the same concentrations of active compounds did not significantly damage plant DNA. Taken together, the findings demonstrated that in commercial formulations, the combined effects of the pure compounds and solvents or other substances included in the product might occur and consequently interfere with the genotoxic potential of the active compounds. Although the cytotoxicity was of the same order of magnitude for both S-metolachlor and mesotrione, mesotrione alone appears to be more genotoxic than S-metolachlor.