The in vivo metabolite patterns of 2,5-difluoroaminobenzene and of its nitrobenzene analogue, 2,5-difluoronitrobenzene, were determined using 19F NMR analysis of urine samples. Results obtained demonstrate significant differences between the biotransformation patterns of these two analogues. For the aminobenzene, cytochrome P450 catalysed aromatic hydroxylation presents the main metabolic pathway. 2,5-Difluoronitrobenzene was predominantly metabolised through glutathione conjugation leading to excretion of 5-fluoro-2-(N-acetylcysteinyl)-nitrobenzene and fluoride anions, and, to a minor extent, through cytochrome P450 catalysed hydroxylation and nitroreduction. Pretreatment of the rats with various inducers of cytochrome P450 enzymes, known also to influence glutathione S-transferase enzyme patterns, followed by exposure to the 2,5-difluoroamino- or 2,5-difluoronitrobenzene, generally resulted in metabolite patterns that varied only to a small (< or = 12%) extent. Based on these results it was concluded that the biotransformation enzyme pattern is not the predominant factor in determining the metabolic route of these two model compounds. Additional in vitro microsomal and cytosolic incubations with 2,5-difluoroaminobenzene and 2,5-difluoronitrobenzene qualitatively confirmed the in vivo results. NADPH/oxygen supported microsomal cytochrome P450 catalysed hydroxylation was observed only for 2,5-difluoroaminobenzene whereas cytosolic GSH conjugation occurred only in incubations with 2,5-difluoronitrobenzene as the substrate. Outcomes from molecular orbital calculations provided a working hypothesis that can explain the difference in metabolic pathways of the nitro- and aminobenzene derivative on the basis of their chemical characteristics. This hypothesis states that the chances for a nitro- or aminobenzene derivative to enter either a cytochrome P450 or a glutathione conjugation pathway are determined by the relative energy levels of the frontier orbitals of the compounds. The aminobenzene derivative has relatively high energy molecular orbitals leading to an efficient reaction of its highest occupied molecular orbital (HOMO) with the singly occupied molecular orbital of the cytochrome P450 (FeO)3+ intermediate, but a low reactivity of its lowest unoccupied molecular orbital (LUMO) with the HOMO of glutathione. The nitrobenzene, on the other hand, has molecular orbitals of relatively low energy, explaining the efficient interaction, and, thus, reaction between its LUMO and the HOMO electrons of glutathione, but resulting in low reactivity with the SOMO electron of the cytochrome P450 (FeO)3+ reaction intermediate.

中文翻译：

---

与分子轨道底物特征相比，2,5-二氟硝基苯和2,5-二氟氨基苯的不同代谢途径。

使用尿液样品的19F NMR分析确定了2,5-二氟氨基苯及其硝基苯类似物2,5-二氟硝基苯的体内代谢模式。获得的结果表明这两种类似物的生物转化模式之间存在显着差异。对于氨基苯，细胞色素P450催化的芳香族羟基化反应是主要的代谢途径。2,5-二氟硝基苯主要通过谷胱甘肽共轭代谢，导致5-氟-2-（N-乙酰基半胱氨酰基）-硝基苯和氟阴离子排泄，并在较小程度上通过细胞色素P450催化的羟基化和硝基还原代谢。用各种也可以影响谷胱甘肽S-转移酶模式的细胞色素P450酶诱导剂对大鼠进行预处理，然后将其暴露于2 5-二氟氨基-或2,5-二氟硝基苯通常会导致代谢物模式变化很小（<或= 12％）。基于这些结果，可以得出结论，生物转化酶模式不是决定这两种模型化合物代谢途径的主要因素。与2,5-二氟氨基苯和2,5-二氟硝基苯的其他体外微粒体和胞质孵育定性地证实了体内结果。NADPH /氧气支持的微粒体细胞色素P450催化的羟基化反应仅在2,5-二氟氨基苯中观察到，而胞质GSH偶联仅在以2,5-二氟硝基苯为底物的孵育中发生。分子轨道计算的结果提供了一个可行的假设，该假设可以根据硝基苯和氨基苯衍生物的化学特性来解释其代谢途径的差异。该假设指出，硝基或氨基苯衍生物进入细胞色素P450或谷胱甘肽偶联途径的机会取决于化合物前沿轨道的相对能级。氨基苯衍生物具有相对较高的能量分子轨道，从而导致其最高占据分子轨道（HOMO）与细胞色素P450（FeO）3+中间体的单个占据分子轨道的有效反应，但其最低未占据分子轨道的反应性较低（LUMO）与谷胱甘肽的HOMO。另一方面，硝基苯