Advanced metabolomics-based approach to reveal new insights into Bisphenol A metabolism and its presence in human excreta and water bodies in Taiwan

Bisphenol A (BPA) is an environmental contaminant and can be detected in foodstuffs. Hence, investigating BPA metabolism in humans is crucial because certain BPA metabolites may exhibit similar or even greater be toxicity than does the parent compound. In this study, we used an advanced metabolomics-based data processing approach along with ultraperformance liquid chromatography-mass spectrometry (UPLC-MS) to identify BPA metabolites in human liver enzyme incubation samples, and those metabolites were further detected in human excreta and water body samples in Taiwan. The first stage involved converting full-scan MS files from the incubation samples into feature information; this stage revealed 1056 and 2472 features with dose-response relationships in the BPA and isotopically labeled BPA incubation datasets, respectively. The second stage involved using stable isotope tracing to identify isotopic pairs from the two datasets; this stage revealed 190 isotopic pairs. An additional dose-response experiment was conducted to confirm that all these features with isotopic pairs also exhibited a dose-response relationship. To focus on the primary BPA metabolite features, we excluded those with low intensities (below 50,000). This left us with 86 features, which we then used for our analysis. To confirm these features as possible BPA metabolites, we compared the tandem MS (MS/MS) spectra between BPA and isotopically labeled BPA incubation samples. The results revealed 75 isotopic pairs with matching isotopically labeled MS/MS spectra. Among these identified features, one feature's m/z value matched to that of a previously reported BPA metabolite, and the other 74 features were novel. However, only 9 of them had proposed structures. We further investigated whether these features could be detected in humans or Taiwanese water bodies. Furthermore, 10 and 2 novel metabolites were identified in human urine and fecal samples, respectively; 17 novel metabolites were identified in the water samples. These findings indicate some of these novel metabolites are present not only in humans but also in various water bodies across Taiwan. These identified metabolites are phase I BPA metabolites, suggesting they may have toxic properties. Further research is warranted to investigate the structures of these newly discovered metabolites and assess their potential human health risks.