Hepatic demethylation of methoxy-bromodiphenyl ethers and conjugation of the resulting hydroxy-bromodiphenyl ethers in a marine fish, the red snapper, Lutjanus campechanus, and a freshwater fish, the channel catfish, Ictalurus punctatus

Marine natural products

“…Methoxy-bromodiphenyl ethers (MeO-BDEs) are susceptible to CYP-450 oxidative demethylation by hepatic microsomes of the red snapper Lutjanus campechanus , with the phenolic products being similar to those formed by oxidation of BDE flame retardants. 633 The phenols are in turn susceptible to glucuronidation and sulfation excretion mechanisms by the same fish species.…”

Methylation and Demethylation of Emerging Contaminants Changed Bioaccumulation and Acute Toxicity in Daphnia magna

“…The occurrence of numerous contaminants of emerging concern (CECs) in the effluent from wastewater treatment plants (WWTPs) and impacted aquatic environments has been extensively reported. − Many CECs contain reactive functional groups, such as hydroxyl, carboxyl, and amide groups, making them susceptible to various biotic and abiotic transformation reactions. − However, most research has focused on the parent form of CECs while generally neglecting their transformation products (TPs) that are often in coexistence. Transformations, such as methylation and demethylation, have been observed in various environmental matrices for many CECs. ,− For example, previous studies showed the co-occurrence of methylated TPs of triclosan, bisphenol A (BPA), tetrabromobisphenol A (TBBPA), and acetaminophen under biotic and/or abiotic conditions with their parent forms. ,,− On the other hand, demethylation is a major metabolism pathway for CECs in biological systems, as observed for CECs such as naproxen and diazepam in humans. , …”

“…Moreover, changes in ecotoxicological profiles induced by the same transformation may be specific to different chemical structures. For instance, methylated products of diclofenac, BPA, triclosan, and 6-OH-BDE-47 all displayed enhanced toxicity or bioaccumulation potential in aquatic organisms, likely due to their increased hydrophobicity (log K ow ) after methylation. ,− , However, methylated TBBPA ethers showed significantly lower acute toxicity in earthworms as compared to TBBPA, despite of increases in their log K ow values . To date, ecotoxicological consequences as a result of methylation or demethylation have yet to be systematically evaluated.…”