Production mechanism of hydroxylated PCBs by oxidative degradation of selected PCBs using TiO2 in water and estrogenic activity of their intermediates.
Production mechanism of hydroxylated PCBs by oxidative degradation of selected PCBs using TiO2 in water and estrogenic activity of their intermediates.
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DOI：
10.1021/es050791a
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发表时间：
2005-10
影响因子：
11.4
通讯作者：
K. Nomiyama;T. Tanizaki;H. Ishibashi;K. Arizono;R. Shinohara
中科院分区：
文献类型：
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作者：
K. Nomiyama;T. Tanizaki;H. Ishibashi;K. Arizono;R. Shinohara
研究了二氧化钛(TiO2)对多氯联苯[2，3，3‘，4’-四氯苯(BZ编号：CB56)、2，3‘，4’，5-四氯苯(CB70)和3，4，4‘，5-四氯苯(CB81：共面PCB)]在水中的氧化光解行为。主要目的是阐明原始多氯联苯和二氧化钛氧化中间体之间的结构关系，并评价处理后的多氯联苯在氧化反应中的雌激素活性。约90%的三种四溴联苯在120分钟内分解。鉴定和定量了三种四氯甲烷分解的中间体，如一些羟基四氯甲烷和羟基三氯甲烷，羧基中间体，酚类中间体，以及苯环裂解产生的其他中间体。在降解途径中，辐照60min内，OH-TRACB和OH-TriCB的产生量增加。用酵母双杂交系统检测人雌激素受体α(HERpha)，评价了三种四氯甲烷中间体在水中的雌激素活性。在辐射时间为60min的条件下，CB81的降解产物具有最大的雌激素活性。我们发现，在60-120min的辐照时间下，溶液中含有多个4-OH-四CBs和4-OH-triCBs，在对位和对位上被OH和Cl取代。推测4-羟基-多氯联苯的化学结构类似于17β-雌二醇(β-E_2)，这些中间体具有很强的雌激素样活性。此外，我们了解到，从一些低毒的多氯联苯同系物转化为强雌激素的羟基多氯联苯的可能性很高。
The oxidative photodegradation behaviors of selected polychlorinated biphenyls (PCBs) [2,3,3',4'-tetraCB (BZ number: CB56), 2,3',4',5-tetraCB (CB70), and 3,4,4',5-tetraCB (CB81: coplanar PCB)] using titanium dioxide (TiO2) in water were investigated. The main purposes were to clarify the structural relation between the original PCBs and the intermediates derived by TiO2 oxidation and to evaluate the estrogenic activity in the treated PCBs during the oxidative reactions. Approximately 90% of the three tetraCBs decomposed within 120 min. Intermediates by decomposition of three tetraCBs, such as some OH-tetraCBs and OH-triCBs, carboxylic intermediates, phenolic intermediates, and other intermediates produced by the cleavage of a benzene ring were identified and quantified. In the degradation pathways, the produced amounts of OH-tetraCB and OH-triCB increased within 60 min of irradiation time. Estrogenic activities of the intermediates from the three tetraCBs in water were assessed by using a yeast two-hybrid assay system for human estrogen receptor alpha (hERalpha). The maximal estrogenic activities were induced by the solutions of decomposed CB81 with irradiation time at 60 min. We found that the solutions at an irradiation time of 60-120 min contained several 4-OH-tetraCBs and 4-OH-triCBs substituted with OH and Cl at para- and para'-positions. It is presumed that the chemical structures of the 4-OH-PCBs are similar to that of 17beta-estradiol (beta-E2); these intermediates present strong estrogenic activities. Moreover, we learned that there is a high possibility of conversion from some low toxic PCBs congeners to strong estrogenic OH-PCBs.