Plant Uptake and Metabolism of 2,4-Dibromophenol in Carrot: In Vitro Enzymatic Direct Conjugation

Abstract

Plants can extensively uptake organic contaminants from soil and subsequently transform them into various products. Those compounds containing hydroxyl may undergo direct conjugation with endogenous biomolecules in plants, and potentially be preserved as conjugates, thus enabling overlooked risk via consumptions of food crops. In this study, we evaluated the uptake and metabolism of 2,4-dibromophenol (DBP) by both carrot cells and whole plant. DBP was completely removed from cell cultures with a half-life of 10.8 h. Four saccharide conjugates, three amino acid conjugates, and one phase I metabolite were identified via ultraperformance liquid chromatography quadrupole time-of-flight mass spectrometry analysis. The dibromophenol glucopyranoside (glucose conjugate) was quantitated by synthesized standard and accounted for 9.3% of the initial spiked DBP at the end of incubation. The activity of glycosyltransferase was positively related to the production of 2,4-dibromophenol glucopyranoside ( p = 0.02, R = 0.86), implying the role of enzymatic catalysis involved in phase II metabolism.

Metabolism of typical halogenated organic pollutants in plants

“…甲基化反应可以改变外 源污染物的生物可利用性和生物活性等, 在外源性物 质的代谢途径中起到十分重要的作用 [37,38] . SULTs一 [39] . 在GSTs 的作用下, 还原态的GSH可与亲电的有机污染物发生 亲核加成反应或者亲核取代反应 [28] .…”

“…DDT在大豆和小麦的悬浮细胞中 会生成与葡萄糖结合的产物 [20,85] . 2,4-二溴酚暴露于 胡萝卜细胞5 d后, 糖基化的产物占到总暴露量的 侯兴旺等: 典型卤代有机污染物在植物体内的代谢过程 9.3% [39] . TBBPA在淡水微藻中也会生成与葡萄糖结合 的产物 [83] , 而在人体血液和尿液中均能检测到TBBPA 与葡萄糖醛酸结合的产物 [81,82] .…”

“…2,4-二溴酚暴露于胡萝卜细胞5 d后, 同样可以检测到 母体物质与丙氨酸、乙酰丙氨酸结合的产物 [39] . 活体 和离体实验均证明苯丙烯酸在植物作用下能生成两种 与GSH结合的产物 [94,95] .…”

Multiple Metabolic Pathways of 2,4,6-Tribromophenol in Rice Plants

“…39,40 For the hydroxylation metabolism in this work, the bromine atom was replaced by a hydroxyl to form dihydroxyl dibromophenol (TP 266 ), similar to the metabolism of 2,4-dibromophenol in carrot cell cultures. 21 Debromination and hydroxylation were generally considered to be representative of phase I metabolism.…”

“…20 Additionally, 2,4-dibromophenol was metabolized to form saccharide and amino acid conjugates in carrots. 21 Only limited types of metabolites and a hint of the environmental fates of bromophenols have been reported. Thus, a systematic search for the biotransformation products and the discovery of new metabolism pathways for bromophenols are critically needed.…”