Department of Environmental Science, University of California, Riverside, CA, 92521, United States; MOE Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, China.
MOE Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, China.
Environ Pollut. 2020 Oct;265(Pt B):114886. doi: 10.1016/j.envpol.2020.114886. Epub 2020 May 29.
Mono-(2-ethylhexyl) phthalate (MEHP) is the primary monoester transformation product of the commonly used plasticizer, di-2-ethylhexyl phthalate (DEHP), and has been frequently detected in various environmental compartments (e.g., soil, biosolids, plants). Plants growing in contaminated soils can take up MEHP, and consumption of the contaminated plants may result in unintended exposure for humans and other organisms. The metabolism of MEHP in plants is poorly understood, but critical for evaluating the potential human and environmental health risks. The present study represents the first attempt to explore the metabolic fate of MEHP in plants. We used Arabidopsis thaliana cells as a plant model and explored metabolic pathways of MEHP using deuterium stable isotope labelling (SIL) coupled with time-of-flight high resolution mass spectrometer (TOF-HRMS). A. thaliana rapidly took up MEHP from the culture medium and mediated extensive metabolism of MEHP. Combining SIL with TOF-HRMS analysis was proved as a powerful method for identification of unknown MEHP metabolites. Four phase Ⅰ and three phase Ⅱ metabolites were confirmed or tentatively identified. Based on the detected transformation products, hydroxylation, oxidation, and malonylation are proposed as the potential MEHP metabolism pathways. In cells, the maximum fraction of each transformation product accounted for 2.8-56.5% of the total amount of metabolites during the incubation. For individual metabolites, up to 2.9-100% was found in the culture medium, suggesting plant excretion. The results in the cell culture experiments were further confirmed in cabbage and A. thaliana seedlings. The findings suggest active metabolism of MEHP in plants and highlight the need to include metabolites in refining environmental risk assessment of plasticizers in the agro-food systems.
邻苯二甲酸二（2-乙基己基）酯（DEHP）是常用增塑剂邻苯二甲酸二异辛酯（DEHP）的主要单酯转化产物，已在各种环境介质（如土壤、生物固体、植物）中频繁检出。生长在受污染土壤中的植物可以吸收 MEHP，而食用受污染的植物可能会导致人类和其他生物体意外暴露。植物中 MEHP 的代谢过程了解甚少，但对于评估潜在的人类和环境健康风险至关重要。本研究首次尝试探索 MEHP 在植物中的代谢命运。我们使用拟南芥细胞作为植物模型，使用氘稳定同位素标记（SIL）结合飞行时间高分辨率质谱（TOF-HRMS）探索 MEHP 的代谢途径。拟南芥细胞从培养基中快速摄取 MEHP，并介导 MEHP 的广泛代谢。将 SIL 与 TOF-HRMS 分析相结合被证明是鉴定未知 MEHP 代谢物的有力方法。鉴定并初步确定了 4 种 I 相和 3 种 II 相代谢物。根据检测到的转化产物，提出了羟基化、氧化和丙二酰化可能是 MEHP 的代谢途径。在细胞中，每种转化产物的最大分数在孵育期间占代谢物总量的 2.8-56.5%。对于个别代谢物，在培养基中发现的比例高达 2.9-100%，这表明植物排泄。细胞培养实验的结果在甘蓝和拟南芥幼苗中得到进一步证实。研究结果表明 MEHP 在植物中具有活跃的代谢，强调需要将代谢物纳入到对农业食品系统中增塑剂的环境风险评估中进行细化。
