Biotransformation of bisphenol-A bis(diphenyl phosphate): In vitro, in silico, and (non-) target analysis for metabolites in rat and bird liver microsomal models. (January 2023)

• Record Type: Journal Article
• Authors: Herczegh, Sofia M.; Chu, Shaogang; Letcher, Robert J.
• Is Part Of: Chemosphere. Volume 310(2023)
• Publication Date: 2023-01
• Subjects: Organophosphate esters -- Biotransformation and metabolism -- In silico -- In vitro -- Bird and rat models -- Non-target analysis; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.136796
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Increased production and usage of organophosphate esters (OPEs) as flame retardants and plasticizers has trended towards larger and 'novel' (oligomeric) OPEs, although there is a dearth of understanding of the environmental fate, stability, toxicokinetics, biotransformation and bioaccumulation of novel OPEs in exposed biota. The present study characterized in vitro biotransformation of the novel OPE bisphenol-A bis(diphenyl phosphate) (BPADP) using Wistar-Han rat and herring gull liver based microsomal assays. Hypothesized target metabolites bisphenol-A (BPA) and diphenyl phosphate (DPHP) and other metabolites were investigated by applying a lines of evidence approach. In silico modelling predicted both BPA and DPHP as rat metabolites of BPADP, these metabolites were quantified via UHPLC-QQQ-MS/MS. Additional non-target metabolites were determined by UHPLC-Q-Exactive-Orbitrap-HRMS/MS and identified by Compound Discoverer software. Mean BPADP depletion of 44 ± 10% was quantified with 3.9% and 2.6% conversion to BPA and DPHP, respectively, in the rat assay. BPADP metabolism was much slower when compared to the well-studied OPE, triphenyl phosphate (TPHP). BPADP depletion in gull liver assays was far slower relative to the rat. Additional non-target metabolites identified included two Phase I, O-dealkylation products, five Phase I oxidation products and one Phase II glutathione adduct, demonstrating agreement between lines of in vitro and in silico evidence. Lines of evidence suggest that BPADP is biologically persistent in exposed mammals or birds. These findings add to the understanding of BPADP stability and biotransformation, and perhaps of other novel OPEs, which are factors highly applicable to hazard assessments of exposure, persistence and bioaccumulation in biota. Graphical abstract: Image 1 Highlights: 44% bisphenol-A bis(diphenyl phosphate) (BPADP) in vitro was depleted in rat assays. In rat assays 2.6% and 3.9% of BPADP was converted to DPHP and BPA, respectively. No significant BPADP depletion or BPA and DPHP formation in herring gull assays. In silico estimation of metabolites BPA and DPHP confirmed by rat and gull assays. Other BPADP oxidation metabolites and conjugate identified by non-target screening.