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Cyclopenta-fused isomers of benz[a]anthracene identification of major microsomal metabolites

Cyclopenta-fused isomers of benz[a]anthracene identification of major microsomal metabolites. Sangaiah, R.; Gold, A.; Easterling, G. E. R.; Watts, R.; Bryant, B J. (Health Effects Res. Lab., Research Triangle Park, NC, USA). Report, EPA-600/D-84-179; Order No. PB84-212745, 26 pp. Avail. NTIS From: Gov. Rep. Announce. Index (U. S.) 1984, 84(20), 37 (English) 1984. DOCUMENT TYPE: Report CA Section: 4 (Toxicology) The microsomal metab. of cytochrome P 450-mediated bioactivation of polycyclic arom. hydrocarbons (PAHs) was investigated. Four cyclopenta-PAH isomers, benz[k]acephenanthrylene (I) [212-41-9], benz[e]aceanthrylene B[e]A [199-54-2], benz[j]aceanthrylene B[j]A [202-33-5], and benz[l]aceanthrylene B[l]A [211-91-6], were formed. The metabolite profiles of these PAHs were detd. with Aroclor 1254-, 5,6-benzoflavone-, and phenobarbital-induced rat liver microsomes and the major metabolites unequivocally identified. In accord with the expected reactivity of the cyclopenta double bond towards epoxidn., the corresponding dihydrodiols were major metabolites of each of the PAHs. For B[l]A and B[j]A, metabolites at the K-region are also obsd. For B[e]A, the formation of the 9,10-dihydrodiol (distal to the pseudo bay formed by the cyclopenta ring) is another major pathway.

Mutagenicity of cyclopenta-fused isomers of benz[a]anthracene in bacterial and rodent cells and identification of the major rat liver microsomal metabolites

Mutagenicity of cyclopenta-fused isomers of benz[a]anthracene in bacterial and rodent cells and identification of the major rat liver microsomal metabolites. Nesnow, Stephen; Leavitt, Sharon; Easterling, Robert; Watts, Randall; Toney, Stephanie H.; Claxton, Larry; Sangaiah, R.; Toney, Glen E.; Wiley, James; et al. (Environ. Prot. Agency, Research Triangle Park, NC 27711, USA). Cancer Res., 44(11), 4993-5003 (English) 1984. CODEN: CNREA8. ISSN: 0008-5472. DOCUMENT TYPE: Journal CA Section: 4 (Toxicology) The microsomal metabolites and mutagenic activity of 4 cyclopenta-fused benz[a]anthracenes, benz[j]aceanthrylene [B(j)A](I) [202-33-5], benz[e]aceanthrylene [B(e)A](II) [199-54-2], benz[l]aceanthrylene [B(l)A](III) [211-91-6], and benz[k]acephenanthrylene [B(k)A](IV) [212-41-9], were studied. Aroclor 1254-induced rat liver microsomes metabolized B(j)A to B(j)A-1,2-dihydrodiol [93673-36-0], B(j)A-9,10-dihydrodiol [93673-37-1], B(j)A-11,12-dihydrodiol [93673-38-2], and 10-hydroxy-B(j)A [93673-39-3]; B(e)A to B(e)A-1,2-dihydrodiol [93673-40-6], B(e)A-3,4-dihydrodiol [93673-41-7], and B(e)A-5,6-dihydrodiol [93673-42-8]; B(l)A to B(l)A-1,2-dihydrodiol [93779-59-0], B(l)A-4,5-dihydrodiol [93673-43-9], and B(l)A-7,8-dihydrodiol [93673-44-0]; and B(k)A to B(k)A-4,5-dihydrodiol [93673-45-1] and B(k)A-8,9-dihydrodiol [93673-46-2]. With each polycyclic arom. hydrocarbon, metab. occurred on the cyclopenta ring. All 4 isomers were active as gene mutagens in Salmonella typhimurium and Chinese hamster 79 cells. In the S. typhimurium mutation studies, using Aroclor 1254-induced rat liver S9, B(j)A, B(e)A, and B(l)A required significantly less microsomal protein for maximal mutation response than B(k)A and B(a)P, suggesting a 1-step activation mechanism, presumably on the cyclopenta-fused ring. B(j)A, B(e)A, and B(l)A were significantly more mutagenic than B(k)A and B(a)P in S. typhimurium. In the Aroclor 1254-induced rat liver S9-mediated V-79 mutagenesis system, all 4 isomers were active, with B(l)A the most active. When Syrian hamster embryo cells were used as the metabolic activation component for V-79 cells, only B(l)A produced a significant response and was equiv. in activity to B(a)P. A helical configuration for B(l)A is inferred from the identification of 2 trans-B(l)A-1,2-dihydrodiols which were synthesized, sepd., and characterized. The metabolically formed dihydrodiol is anti-trans-B(l)A-1,2-dihydrodiol [93673-35-9] and exptl. evidence suggests that the metabolically formed B(l)A-1,2-oxide is the anti-isomer. Synthetic B(l)A-1,2 oxide was a direct-acting mutagen in S. typhimurium and Chinese hamster V-79 cells and is estd. to account for up to 40% of the mutagenic activity of the parent hydrocarbon. Therefore, certain cyclopenta-ring fusions on benz[a]anthracene appear to markedly increase its genotoxic and carcinogenic activities.