Reed G A, Curtis J F, Mottley C, Eling T E, Mason R P
Proc Natl Acad Sci U S A. 1986 Oct;83(19):7499-502. doi: 10.1073/pnas.83.19.7499.
The (bi)sulfite ion undergoes extensive autoxidation in neutral aqueous media with the formation of sulfur trioxide radical anion that is detected by ESR. The radical anion subsequently reacts with molecular oxygen to form a peroxyl radical. We find that when (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) is included in this autoxidation system, BP-7,8-diol is converted to diolepoxides, ultimate carcinogenic derivatives of benzo[a]pyrene. This epoxidation occurs with a stereoselectivity consistent with either a peroxyl radical or a peracid as the epoxidizing agent. The epoxidation is dependent on the concentration of both (bi)sulfite and oxygen. In the presence of 10 microM butylated hydroxyanisole, which abolishes (bi)sulfite autoxidation, no (bi)sulfite-dependent epoxidation occurs. These results are discussed in regard to the mechanism of (bi)sulfite autoxidation, and in relationship to the cocarcinogenicity of sulfur dioxide [anhydrous (bi)sulfite] for benzo[a]pyrene-induced pulmonary neoplasia.
亚硫酸氢根离子在中性水介质中会发生广泛的自氧化反应，生成可通过电子自旋共振（ESR）检测到的三氧化硫自由基阴离子。该自由基阴离子随后与分子氧反应形成过氧自由基。我们发现，当（±）-反式-7,8-二羟基-7,8-二氢苯并[a]芘（BP-7,8-二醇）包含在该自氧化体系中时，BP-7,8-二醇会转化为二环氧物，即苯并[a]芘的最终致癌衍生物。这种环氧化反应具有立体选择性，与过氧自由基或过酸作为环氧化剂一致。环氧化反应取决于亚硫酸氢根离子和氧气的浓度。在存在10微摩尔叔丁基对苯二酚的情况下，叔丁基对苯二酚会消除亚硫酸氢根离子的自氧化反应，此时不会发生亚硫酸氢根离子依赖的环氧化反应。我们将结合亚硫酸氢根离子自氧化反应的机制以及二氧化硫（无水亚硫酸氢根离子）对苯并[a]芘诱导的肺部肿瘤的促癌作用来讨论这些结果。
