Transformation of the new antifouling compound Irgarol 1051 by Phanerochaete chrysosporium

Irgarol 1051, 2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine, is a newly developed herbicidal additive for use in copper-based antifouling paints. It is intended to replace the antifouling agent tributyltin, which has been regulated internationally due to its severe impact on the aquatic ecosystem. However, there is no information in the open literature on the persistence and degradation of Irgarol, a fact that hinders the assessment of its ultimate impact on the environment. This study showed that the white rot fungus Phanerochaete chrysosporium was capable of biotransforming Irgarol 1051. It appears that the metabolism of Irgarol by the fungus proceeds mainly via partial N-dealkylation. Metabolic dealkylation occurs at the cyclopropylamino group resulting in metabolite M1, which has tentatively been identified as 2-methylthio-4-tert-butylamino-6-amino-s-triazine. M1 appeared to be a stable and/or terminal metabolite. No evidence of the heterocyclic ring cleavage of Irgarol 1051 was observed, thus implying a possibility of its degradation product(s) accumulating in the environment.