Identification of plant metabolites of environmental contaminants by UPLC-QToF-MS: The in vitro metabolism of triclosan in horseradish

Plants can extensively transform contaminants after uptake through phase I and phase II metabolism to a large diversity of products. UPLC-QToF-MS was used to detect and identify metabolites of the bacteriostatic agent triclosan in a horseradish hairy root culture. Thirty-three metabolites of triclosan were recognized by a stepwise approach of mass defect filtering, multivariate data analysis, and isotope pattern filtering from a data set of several thousands of signals in the exposed culture. Structure proposals were elaborated for 23 triclosan metabolites on the basis of their MS data. The majority were identified as conjugates (phase II metabolites) such as saccharides or sulfosaccharides. Additionally, a disulfosaccharide was identified as a plant metabolite for the first time. Besides that, also conjugates of a phase I metabolite, hydroxytriclosan, were determined in horseradish tissue extracts. Dehalogenation products of triclosan were not observed. The large number of metabolites detected and identified in this study emphasizes the importance of a comprehensive analytical approach in studies on the uptake and fate of organic contaminants in plants.