Hydroperoxide-dependent oxygenation of -7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene by ram seminal vesicle microsomes. Source of the oxygen |
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Authors: | Lawrence J Marnett Michael J Bienkowski |
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Institution: | Department of Chemistry Wayne State University Detroit, MI 48202 USA |
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Abstract: | Incubation of 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid with ram seminal vesicle microsomes (RSVM) triggers the oxygenation of -7,8-dihydroxy-7,8-dihydrobenzoa]pyrene (BP-7,8-diol). The principal oxidation products are 7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenzoa]pyrenes which are non-enzymatic hydrolysis products of r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzoa]pyrene. At short incubation times, an additional product is isolated which is identified as r-7,t-8,t-9-trihydroxy-c-10-methoxy-7,8,9,10-tetrahydrobenzoa]pyrene. This product appears to arise by solvolysis of the extracted diolepoxide during high performance liquid chromatography using methanol-water solvent systems. The incubation of 18O-labeled 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid with BP-7,8-diol and RSVM leads to very little incorporation of 18O into the stable solvolysis products (analyzed by gc-ms of their peracetates). Parallel incubations conducted with 16O-labeled hydroperoxide under an 18O2 atmosphere indicate that the principle source of the epoxide oxygen is molecular oxygen. |
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