Cross‐Coupling of Phenolic Humus Constituents and 2,4‐Dichlorophenol

Various phenolic compounds occurring in soil can be incorporated into humus complexes by microbial activity. In this study experiments were carried out in which a phenoloxidase isolated from the fungus Rhizoctonia praticola was incubated with humus constituents such as orcinol, syringic acid, vanillic acid, and vanillin individually and in the presence of 2,4‐dichlorophenol. Oligomeric products, dimers to pentamers, were formed by oxidative coupling as determined by mass spectrometry. The combined incubation of naturally occurring phenols and 2,4‐dichlorophenol, a main product of various herbicides, resulted in the formation of cross‐coupling products. The occurrence of such processes in soil may lead to the incorporation of xenobiotic compounds into soil organic matter by enzymatic activity, and thus prolong their persistence in soil.