Hydroxy-PCBs, methoxy-PCBs and hydroxy-methoxy-PCBs: metabolites of polychlorinated biphenyls formed in vitro by tobacco cells.

While the metabolism of polychlorinated biphenyls (PCBs) in plant cells is a rarely studied field, hydroxy-PCBs have been detected in several studies involving the use of various plant species. The ability of the tobacco (Nicotiana tabacum) callus culture WSC-38 to metabolize six dichlorobiphenyls under aseptic conditions was studied, and the resulting PCB metabolites were analyzed. WSC-38 cultures were cultivated with individual dichlorinated PCB congeners. The metabolites were identified based on mass spectra characteristics after gas chromatography separation. In addition, metabolites of PCB 9 (2,5-dichlorobiphenyl) were identified by comparing their retention characteristics with the available standards. In most cases at least two hydroxy-PCBs were produced from each parent PCB. Methoxy-PCBs and hydroxy-methoxy-PCBs were other groups of metabolites produced. To the best of our knowledge, ours is the first report to determine the presence of methoxy- and hydroxy-methoxy-metabolites of PCBs in plants. The role of the O-methyltransferases (OMTs) in the methylation of hydroxy-PCBs is discussed. As methoxy-metabolites of acetophenone were found among our samples, we posit that the OMTs responsible for the methylation of these compounds are also involved in the metabolism of PCBs in cultures of WSC-38.