"Targeted and untargeted metabolomics using high resolution mass spectrometry and multivariate statistical analysis, coupled with 14C-labeled chemicals studies were used to identify novel phytometabolites and quantify the fate of common antimicrobials in plant tissues. Triclocarban (TCC), an antimicrobial that is commonly found in personal care products, was metabolized by jalapeno pepper plants during long-term exposure (12 weeks), leading to the formation of several phase I transformation products (e.g. 2'-OH-TCC and 6-OH-TCC) and phase II glycosylated OH-TCC. Importantly, the concentrations of TCC metabolites were more than 20 times greater than the concentrations of TCC in the above-ground tissues of the pepper plants after 12 weeks. Approximately 95.6% of the TCC was present as metabolites in the fruits. For sulfonamides, upon exposure to the model plant Arabidopsis thaliana, sulfamethazine (SMT) and sulfamethoxazole (SMX) were also prone to extensive metabolism in plant tissues. Untargeted screening of extractable metabolites revealed that glycosylated conjugates were the most abundant metabolites, which accounted for 80--90% of the total metabolites in plant tissues. Other conjugates, such as pterin- and methylsalicyclate-, were present at lower concentrations. Phase I transformation products, such as hydroxyl-, acetyl-, desulfo, and desamino-, were identifed as minor metabolites in plant tissues. For tetracyclines, abiotic transformation and plant metabolism played the key roles in their fate during exposure to Arabidopsis thaliana. Plant metabolism of chlortetracycline (CTC) also led to the formation of glycosylated conjugates and the corresponding 4-epi isomers. More importantly, although CTC was solely added into the experimental reactors, other tetracycline antimicrobials such as tetracycline, 4-epi-tetracycline, demeclocycline, and 4-epi-demeclocycline were detected in the plant tissues. Preliminary studies using soil columns planted with A. thaliana plants showed that phytometabolism of sulfonamides was probably similar with that under hydroponic conditions, with glycosylated conjugates identified as the major phytometabolites. The majority of the uptaken parent sulfonamides and metabolites were found in the plant roots, with limited root-to-shoot translocation. In conclusion, this research indicates that untransformed antimicrobials only represent a small proportion of the total compounds taken up in plant tissues when transformed, conjugated, and sequestered phytometabolites are considered. Consequently, phytometabolism of antimicrobials in planted systems is a critical point for comprehensively addressing human exposure to contaminants of emerging concerns through food chains."--Pages ii-iii.
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