Metabolites of 2,2′-dichlorobiphenyl and 2,6-dichlorobiphenyl in hairy root culture of black nightshade Solanum nigrum SNC-9O

The hairy root culture of black nightshade (Solanum nigrum) SNC-9O was exposed to 2,2′-dichlorobiphenyl (PCB 4) and 2,6-dichlorobiphenyl (PCB 10) to follow the metabolites produced. The analytical standards of 4-hydroxy-2,2′-dichlorobiphenyl, 5′-hydroxy-2,2′-dichlorobiphenyl, 4-hydroxy-2,6-dichlorobiphenyl, 2-hydroxy-2′,6′-dichlorobiphenyl, 3-hydroxy-2′,6′-dichlorobiphenyl and 4-hydroxy-2′,6′-dichlorobiphenyl have been synthesized. Hydroxy-metabolites of both PCB 4 and PCB 10 were present in the biomass. These appeared mainly as conjugates rather than as free hydroxy-PCBs, both maintained in plant cells. The concentrations of non-conjugated hydroxy-PCBs ranged between 0.9 and 35.2 μg kg−1 of biomass fresh weight and the concentration of the conjugated ones ranged between 2.0 and 113.0 μg kg−1 depending on the position of hydroxyl. The para- position of biphenyl (4 or 4′) seems to be preferred for hydroxylation. Methoxy-PCBs and hydroxy–methoxy-PCBs have also been identified in plant cells. Hydroxyl in the meta-position (3, 3′, 5 or 5′) appears to be preferred for methylation in hydroxy-PCBs. Hydroxy–methoxy-PCBs have occurred in the conjugated form as well.

► We identified the metabolites of PCB 4, PCB 10 in hairy roots of Solanum nigrum. ► Hydroxy-PCBs were present rather conjugated than in their free forms. ► Hydroxylation was targeted primarily to -para position of less chlorinated phenyl. ► The natural formation of methoxy-PCBs in plant cells was confirmed. ► Methylation was targeted preferentially to -meta hydroxyl.