Antibiotics can be uptaken by plants from soil desorption or directly from irrigation water, but their metabolization pathways in plants are largely unknown. In this paper, an analytical workflow based on high-resolution mass spectrometry was applied for the systematic identification of biotransformation products of ofloxacin in lettuce. The targeted metabolites were selected by comparing the mass chromatograms of exposed with control samples using an advanced spectra-processing method (Fragment Ion Search). The innovative methodology presented allowed us to identify a total of 11 metabolites, including 5 ofloxacin metabolites that are being reported for the first time in plants. Accordingly, major transformation pathways were proposed revealing insight into how ofloxacin and related chemicals are metabolized in lettuce. Furthermore, the influence of biotransformation on potential residual antimicrobial activity of identified compounds was discussed. Human exposure to antibiotics at doses below the minimum inhibitory concentrations is crucial in human risk assessment, including food ingestion; however, in the case of ofloxacin presented results reveal that plant metabolites should also be considered so as not to underestimate their risk.

植物可以通过土壤解吸或直接从灌溉水中吸收抗生素，但它们在植物中的代谢途径很大程度上未知。本文应用基于高分辨率质谱的分析工作流程对生菜中氧氟沙星生物转化产物进行系统鉴定。使用先进的光谱处理方法（碎片离子搜索），通过比较暴露样品与对照样品的质量色谱图来选择目标代谢物。所提出的创新方法使我们能够鉴定出总共 11 种代谢物，其中包括 5 种首次在植物中报道的氧氟沙星代谢物。因此，提出了主要的转化途径，揭示了氧氟沙星和相关化学物质在生菜中如何代谢的见解。此外，还讨论了生物转化对已鉴定化合物的潜在残留抗菌活性的影响。人类接触低于最低抑菌浓度的抗生素对于人类风险评估（包括食物摄入）至关重要；然而，就氧氟沙星而言，研究结果表明还应考虑植物代谢物，以免低估其风险。