Uptake, translocation, and metabolism of sulfamethazine by Arabidopsis thaliana: distinguishing between phytometabolites and abiotic transformation products in the media

Abstract

Plant accumulation of antibiotic residues presents potential risks to human and ecosystem health. However, the phytometabolic pathways of antibiotics following plant uptake are still largely uncharacterized. This study investigated the phytometabolism of sulfamethazine (SMT) by Arabidopsis thaliana, using ¹⁴C-labeled and unlabeled SMT. SMT was accumulated in both roots and shoots of axenic A. thaliana plants (123.7 ± 12.3 and 22.7 ± 1.0 µg/kg fw, respectively) after 21 days of exposure. However, the parent ¹⁴C-SMT accounted for only 1.7 ± 0.01% of the total ¹⁴C-radioactivity in plant tissues. The majority of ¹⁴C-radioactivity taken up by plants was present as bound residues (42.0–68.2% of initially applied ¹⁴C-SMT), while extractable ¹⁴C-residues accounted for only 7.7–12.6%. A. thaliana metabolized SMT primarily through glycosylation at the N⁴-nitrogen atom. Additionally, other products, including pterin-SMT, methylsalicylate-SMT, N⁴-formyl-SMT, desulfo-SMT, hydroxyl-SMT, N⁴-acetyl-SMT, desamino-SMT, and 2-amino-4,6-dimethylpyrimidine, were also identified. Notably, a portion of the extractable metabolites was excreted into the culture media, requiring characterization of these metabolites as either excreted phytometabolites or abiotic transformation products of SMT based on comparisons between experimental and control reactors.

Keywords:

• Antibiotics
• bound residues
• glycosylation
• phytometabolism
• sulfamethazine
• sulfonamides

Acknowledgments

The authors are thankful to Dr. Hui Li and Dr. Yingjie Zhang for the use of their LC-MS/MS and Dr. Dan Jones and the MSU Mass Spectrometry Research Technology Support Facility.

Disclosure statement

The authors declare no conflict of interest.

Additional information

Funding

This work was supported by the National Science Foundation (NSF) Division of Chemical Bioengineering, Environmental, and Transport Systems [Grant No. 1510203], Vietnam Education Foundation Fellowship, MSU College of Agriculture and Natural Resources, and MSU AgBioResearch (USDA Hatch project MICL02337).