In vitro Phase I metabolism of newly identified plasticizers using human liver microsomes combined with high resolution mass spectrometry and based on non-targeted and suspect screening workflows

Three plasticizers, namely bis (3,5,5-trimethylhexyl) phosphate (TMHPh), di(propylene glycol) dibenzoate (DiPGDB), and tri-n-butyl trimellitate (TBTM), were recently identified and reported in high concentrations in indoor dust from Belgian homes. In this study, their behavior within the human body was investigated by generating Phase I biotransformation products for the first time. Human liver microsomes (HLMs) were used following an in vitro assay and liquid chromatography time of flight mass spectrometry (LC-QTOF-MS) was employed for the analysis. Biotransformation products were identified for TMHPh as products of hydroxylation reactions that took place in one or two positions in the structure of the substrate. For DiPGDB, biotransformation products were formed after hydrolysis of carboxylic esters and oxidative-O-dealkylation. For TBTM, biotransformation products were formed through hydrolysis of the different carboxylic esters of the molecule, in agreement with studies on structurally similar compounds. The generated results can contribute to biomonitoring studies creating new knowledge on human exposure to emerging compounds and on the metabolism of xenobiotics.