Cytochrome P450 induced formation of hydroxylated polybrominated diphenyl ether and dibenzo-p-dioxin derivates from brominated phenols

Detection and O-methylation of bromocatechols, brominated/hydroxylated analogs of diphenyl ethers and dibenzo-p-dioxins in thorny oyster (Spondylus squamosus) and pen shell (Atrina vexillum) from the Philippines

Marine algae in the Asia-Pacific region are known for producing brominated phenols in abundance. This study investigated the presence of brominated catechols and their transformation into brominated dimethoxy diphenyl ethers (diMeO-BDEs) and monomethoxy-dibenzo-p-dioxins (MeO-BDDs) in two bivalve species collected from the coast of Luzon island, the Philippines. Species-difference in brominated profiles were observed between thorny oyster (S. squamosus) and pen shell (Atrina vexillum). In the immature S. squamosus, we identified di- and tribrominated catechols/guaiacols, dihydroxylated tetra-/pentaBDEs (diOH-BDEs), and monohydroxylated tri-/tetrabromo-dibenzo-p-dioxins (OH-BDDs). During the immature stage of S. squamosus, the concentrations of phenolic products were higher in the order of bromocatechols > OH-BDDs > diOH-BDEs. Corresponding MeO analogs, however, increased in the order of MeO-BDDs > diMeO-BDEs > bromoveratroles. It was estimated that 1-2 % of bromophenols and catechols undergo O-methylation, whereas diOH-BDEs and OH-BDDs are nearly completely O-methylated. The interconversions within phenolic products were minimal. The results suggest that S. squamosus produces or acquires phenolic and catecholic products in early larval stage and may undergo O-methylation as it grows, resulting in the accumulation of diMeO-BDEs and MeO-BDDs. This understanding provides important insights into the sources of diOH-BDEs and OH-BDDs, as well as the accumulation mechanisms of their methoxylated derivatives in marine top predators.