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Lorentzen M, Sydnes MO, Jørgensen KB. Enantioselective synthesis of (−)-(1R,2R)-1,2-dihydrochrysene-1,2-diol. Tetrahedron 2014. [DOI: 10.1016/j.tet.2014.10.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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2
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Chiu PL, Yang SK. Liquid Chromatographic Separation of FiveTrans-dihydrodiols of Benz[A] anthracene. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/01483918608076663] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Pei-Lu Chiu
- a Department of Pharmacology , F. Edward Hébert School of Medicine Uniformed Services University of the Health Sciences , Bethesda , Maryland , 20814-4799
| | - Shen K. Yang
- a Department of Pharmacology , F. Edward Hébert School of Medicine Uniformed Services University of the Health Sciences , Bethesda , Maryland , 20814-4799
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3
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Zief M, Crane LJ, Horvath J. Selection of the Mobile Phase for Enantiomeric Resolution via Chiral Stationary Phase Columns. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/01483918408073997] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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4
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Armstrong DW. Chiral Stationary Phases for High Performance Liquid Chromatographic Separation of Enantiomers: A Mini-Review. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/01483918408073942] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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5
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Zajc B, Grahek R, Kocijan A, Lakshman MK, Kosmrlj J, Lah J. Evaluation of the enantiomeric resolution of 7,8-dihydroxy-7,8-dihydrobenzo[a]-pyrene and its 6-fluoro and 6-bromo derivatives on polysaccharide-derived stationary phases. J Org Chem 2003; 68:3291-4. [PMID: 12688804 DOI: 10.1021/jo020607t] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The enantiomeric resolution and the elution order of (+/-)-trans-7,8-dihydrodiols of benzo[a]pyrene and its 6-fluoro and 6-bromo derivatives were analyzed on three polysaccharide-based columns: Daicel Chiralcel CA-I (cellulose triacetate), OF, and OG [cellulose tris(4-chloro- and 4-methylphenylcarbamate)]. For comparison, the separation of (+/-)-1,1'-bi-2-naphthol was evaluated on the OG and OF columns. Possibly similar interactions of (S)-1,1'-bi-2-naphthol and (7S,8S)-isomers of 6-halo-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene with the chiral sorbent are suggested.
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Affiliation(s)
- Barbara Zajc
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana, Slovenia.
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6
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Honey S, O'Keefe P, Drahushuk AT, Olson JR, Kumar S, Sikka HC. Metabolism of benzo(a)pyrene by duck liver microsomes. Comp Biochem Physiol C Toxicol Pharmacol 2000; 126:285-92. [PMID: 11048678 DOI: 10.1016/s0742-8413(00)00121-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The metabolism of benzo(a)pyrene [BP], a model carcinogenic PAH, by hepatic microsomes of two duck species, mallard (Anas platyrhynchos) and common merganser (Mergus merganser americanus) collected from chemically-contaminated and relatively non-contaminated areas was investigated. The rate of metabolism of BP by liver microsomes of common merganser and mallard collected from polluted areas (2,650 +/- 310 and 2,200 +/- 310 pmol/min per mg microsomal protein, respectively) was significantly higher than that obtained with liver microsomes of the two species collected from non-polluted areas (334 +/- 33 and 231 +/- 30 pmol/min per mg microsomal protein, respectively). The level of cytochrome P-450 1A1 was significantly higher in the liver microsomes of both duck species from the polluted areas as compared to the ducks from the non-polluted areas. The major BP metabolites, including BP-9, 10-diol, BP-4, 5-diol, BP-7, 8-diol, BP-1, 6-dione, BP-3, 6-dione, BP-6, 12-dione, 9-hydroxy-BP and 3-hydroxy-BP, formed by liver microsomes of both duck species from polluted and non-polluted areas, were qualitatively similar. However, the patterns of these metabolites were considerably different from each other. Liver microsomes of ducks from the polluted areas produced a higher proportion of benzo-ring dihydrodiols than the liver microsomes of ducks from the non-polluted areas, which converted a greater proportion of BP to BP-phenols. The predominant enantiomer of BP-7,8-diol formed by hepatic microsomes of the two duck species had an (-)R,R absolute stereochemistry. The data suggest that duck and rat liver microsomal enzymes have different regioselectivity but similar stereoselectivity in the metabolism of BP.
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Affiliation(s)
- S Honey
- Environmental Toxicology and Chemistry Laboratory, Great Lakes Center for Environmental Research and Education, State University of New York College at Buffalo, 14222, USA
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7
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8
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Resolution of polycyclic aromatic hydrocarbon dihydrodiols via diastereomeric formaldehyde acetals. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0957-4166(97)00464-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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9
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Tang XQ, Harvey RG. Enantioselective synthesis of the K-region trans-9,10-dihydrodiol of benzo[g]chrysene. Tetrahedron Lett 1995. [DOI: 10.1016/0040-4039(95)01243-b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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10
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Adams JD, Yagi H, Levin W, Jerina DM. Stereo-selectivity and regio-selectivity in the metabolism of 7,8-dihydrobenzo[a]pyrene by cytochrome P450, epoxide hydrolase and hepatic microsomes from 3-methylcholanthrene-treated rats. Chem Biol Interact 1995; 95:57-77. [PMID: 7697754 DOI: 10.1016/0009-2797(94)03354-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The active site of cytochrome P450 1A1 has been probed with the substrate 7,8-dihydrobenzo[a]pyrene using a purified, reconstituted system composed of cytochrome P450 1A1, NADPH-cytochrome c reductase and lipid in the presence or absence of epoxide hydrolase. The turnover of the substrate was found to be 38 nmol/nmol of cytochrome P450/min. The metabolic products that were identified are: a phenolic 7,8-dihydrobenzo[a]pyrene (20-29%); 9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (17-28%); benzo[a]pyrene (12-19%); 7-hydroxy-7,8-dihydrobenzo[a]pyrene (13-16%); 8-hydroxy-7,8-dihydrobenzo[a]pyrene (7-15%); 3-hydroxybenzo[a]pyrene (7-15%); 4,5-epoxy-4,5,7,8-tetrahydrobenzo[a]pyrene (0-4%); and a triol of 7,8,9,10-tetrahydrobenzo[a]pyrene (0-4%). 9,10-Epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene undergoes rapid hydrolysis to cis- and trans-9,10-dihydroxy-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (2:1) by benzylic attack of water at C-10. Approximately 71% of the trans diols are derived from (+)-(9S,10R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, indicating that cytochrome P450 1A1 has more than a 2:1 preference for selective epoxidation of an enantiotopic face of 7,8-dihydrobenzo[a]pyrene. This stereo-selectivity agrees with the postulated stereo-selectivity predicted by a previously described active site model for cytochrome P450 1A1. Epoxide hydrolase in pure form or in hepatic microsomes catalyzes the hydrolysis of 9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, which is inhibited by 1,1,1-trichloropropane 2,3-oxide. The (+)-(9S,10R)-isomer of the epoxide is slightly preferred as a substrate over its enantiomer and is cleaved by benzylic and nonbenzylic attack. Only benzylic attack was found with (-)-(9R,10S)-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene.
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Affiliation(s)
- J D Adams
- University of Southern California, School of Pharmacy, Los Angeles 90033
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11
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Sutherland JB, Fu PP, Yang SK, Von Tungeln LS, Casillas RP, Crow SA, Cerniglia CE. Enantiomeric Composition of the
trans
-Dihydrodiols Produced from Phenanthrene by Fungi. Appl Environ Microbiol 1993; 59:2145-9. [PMID: 16348991 PMCID: PMC182249 DOI: 10.1128/aem.59.7.2145-2149.1993] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The
trans
-dihydrodiols produced during the metabolism of phenanthrene by
Cunninghamella elegans, Syncephalastrum racemosum,
and
Phanerochaete chrysosporium
were purified by high-performance liquid chromatography (HPLC). The enantiomeric compositions and optical purities of the
trans
-dihydrodiols were determined to compare interspecific differences in the regio- and stereoselectivity of the fungal enzymes. Circular dichroism spectra of the
trans
-dihydrodiols were obtained, and the enantiomeric composition of each preparation was analyzed by HPLC with a chiral stationary-phase column. The phenanthrene
trans
-1,2-dihydrodiol produced by
C. elegans
was a mixture of the 1
R
,2
R
and 1
S
,2
S
enantiomers in variable proportions. The phenanthrene
trans
-3,4-dihydrodiol produced by
P. chrysosporium
was the optically pure 3
R
,4
R
enantiomer, but that produced by
S. racemosum
was a 68:32 mixture of the 3
R
,4
R
and 3
S
,4
S
enantiomers. The phenanthrene
trans
-9,10-dihydrodiol produced by
P. chrysosporium
was predominantly the 9
S
,10
S
enantiomer, but those produced by
C. elegans
and
S. racemosum
were predominantly the 9
R
,10
R
enantiomer. The results indicate that although different fungi may exhibit similar regioselectivity, there still may be differences in stereoselectivity that depend on the species and the cultural conditions.
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Affiliation(s)
- J B Sutherland
- National Center for Toxicological Research, Food and Drug Administration, Jefferson, Arkansas 72079; Department of Pharmacology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 ; and Department of Biology, Georgia State University, Atlanta, Georgia 30303
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12
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Weems H, Zamani K. Resolution of terfenadine enantiomers by beta-cyclodextrin chiral stationary phase high-performance liquid chromatography. Chirality 1992; 4:268-72. [PMID: 1389964 DOI: 10.1002/chir.530040411] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Enantiomers of terfenadine were resolved by high-performance liquid chromatography (HPLC) using a chiral stationary phase (CSP) column packed with beta-cyclodextrin (beta-CD) covalently bound to silica. Separation was achieved in both the reverse phase and normal phase modes. Resolution of enantiomers was confirmed by ultraviolet-visible absorption, circular dichroism, and mass spectral analysis.
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Affiliation(s)
- H Weems
- Department of Pharmacology, Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, Maryland 20814-4799
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13
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Weems HB, Yang SK. Resolution of enantiomeric triols, triol-hydroxyethylthioethers, and methoxy-triols derived from three benzo[a]pyrene diol-epoxides by chiral stationary phase high-performance liquid chromatography. J Chromatogr A 1990; 535:239-53. [PMID: 2128494 DOI: 10.1016/s0021-9673(01)88949-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Benzo[a]pyrene 7,8-diol-anti-9,10-epoxide, 7,8-diol-syn-9,10-epoxide, and 9,10-diol-anti-7,8-epoxide were converted to triol, triol-hydroxyethylthioether, and methoxy-triol derivatives. Enantiomeric pairs of these derivatives were resolved by high-performance liquid chromatography with Pirkle's pi-electron acceptor chiral stationary phases. Resolution of enantiomers was confirmed by ultraviolet-visible absorption, circular dichroism, and mass spectral analyses. Relative to those of tetrols, these derivatives are less polar and have shorter retention times and improved enantiomeric resolution on chiral stationary phases. Absolute stereochemistries of most enantiomeric derivatives were deduced by comparing their circular dichroism spectra to those of similar compounds derived from enantiomeric diol-epoxides of known absolute stereochemistry.
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Affiliation(s)
- H B Weems
- Department of Pharmacology, F. Edward Hébert School of Medicine, Uniformed Services University of Health Sciences, Bethesda, MD 20889-4799
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14
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Yang SK, Mushtaq M, Bao ZP, Weems HB, Shou MG, Lu XL. Improved enantiomeric separation of dihydrodiols of polycyclic aromatic hydrocarbons on chiral stationary phases by derivatization to O-methyl ethers. J Chromatogr A 1989; 461:377-95. [PMID: 2708480 DOI: 10.1016/s0021-9673(00)94305-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
K-region trans-dihydrodiol derivatives of phenanthrene, 1-methylphenanthrene, 4,5-methylenephenanthrene, pyrene, 1-bromopyrene, chrysene, benzo[c]phenanthrene, benz[a]anthracene, 1-, 4-, 6-, 7-, 11- and 12-methylbenz[a]anthracenes, 7,12-dimethylbenz[a]anthracene, 3-methylcholanthrene, and benzo[a]pyrene, and non-K-region trans-3,4-dihydrodiols of benz[a]anthracene, chrysene, and 7,12-dimethylbenz[a]anthracene are converted to O-methyl ethers. Enantiomers of these O-methyl ethers are generally more efficiently separated on Pirkle's chiral stationary phases than the enantiomers of underivatized dihydrodiols. O-Methyl ethers are substantially less polar than dihydrodiols, and O-methyl ethers are eluted with shorter retention times. Eluents of lower polarity can hence be used. This enhances chiral interactions between chiral stationary phase and solutes, allowing improved separation of enantiomers.
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Affiliation(s)
- S K Yang
- Department of Pharmacology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799
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15
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Weems HB, Yang SK. Chiral stationary phase high-performance liquid chromatographic resolution and absolute configuration of enantiomeric benzo[a]pyrene diol-epoxides and tetrols. Chirality 1989; 1:276-83. [PMID: 2642055 DOI: 10.1002/chir.530010406] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Enantiomers of diastereomeric benzo[a]pyrene (BP) diol-epoxides, r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydro-BP (BP 7,8-diol-anti-9,10-epoxide), r-7,t-8-dihydroxy-c-9,10-epoxy-7,8,9,10-tetrahydro-BP (BP 7,8-diol-syn-9,10-epoxide), r-9,t-10-dihydroxy-t-7,8-epoxy-7,8,9,10-tetrahydro-BP (BP 9,10-diol-anti-7,8-epoxide), and several 7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrenes (BP tetrols) were resolved by high-performance liquid chromatography (HPLC) using columns packed with either (R)-N-(3,5-dinitrobenzoyl)phenylglycine[(R)-DNBPG] or (S)-N-(3,5-dinitrobenzoyl)leucine [(S)-DNBL], which is either ionically or covalently bonded to gamma-aminopropylsilanized silica. Resolution of enantiomers was confirmed by ultraviolet-visible absorption and circular dichroism spectral analyses. Resolved enantiomers of BP diol-epoxides were each hydrolyzed in acidic solution to a pair of diastereomeric tetrols which were separated by reversed-phase HPLC. Absolute stereochemistries of enantiomeric diol-epoxides were deduced by the absolute configuration of their hydrolysis products.
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Affiliation(s)
- H B Weems
- Department of Pharmacology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799
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Yang SK. Stereoselectivity of cytochrome P-450 isozymes and epoxide hydrolase in the metabolism of polycyclic aromatic hydrocarbons. Biochem Pharmacol 1988; 37:61-70. [PMID: 3276319 DOI: 10.1016/0006-2952(88)90755-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Enantiomeric compositions of epoxides formed in the metabolism of planar benz[a]anthracene (BA), benzo[a]pyrene (BaP), and chrysene (CR), and nonplanar benzo[c]phenanthrene (BcPh), 12-methylbenz[a]anthracene (12-MBA) and 7,12-dimethylbenz[a]anthracene (7,12-DMBA) by liver microsomes from untreated, phenobarbital-treated, and 3-methylcholanthrene-treated rats are determined either by direct chiral stationary phase HPLC analysis or by the enantiomeric compositions of metabolically formed trans-dihydrodiols. Cytochrome P-450 isozymes contained in various liver microsomal preparations have varying degrees of stereoselectivity in catalyzing the epoxidation reactions at various formal double bonds of the polycyclic aromatic hydrocarbons studied. In general, cytochrome P-450c, the major cytochrome P-450 isozyme contained in liver microsomes from 3-methylcholanthrene-treated rats, has the highest degree of stereoselectivity. Regardless of absolute configuration, non-K-region epoxides are converted to trans-dihydrodiols by epoxide hydrolase-catalyzed water attack at the allylic carbon. The S-center of K-region S,R-epoxide enantiomers derived from planar BA, BaP and CR is the major site of epoxide hydrolase-catalyzed water attack. In contrast, the R-center of K-region S,R-epoxide enantiomers derived from nonplanar BcPh, 12-MBA and 7,12-DMBA is the major site of epoxide hydrolase-catalyzed water attack. However, the K-region R,S-epoxide enantiomers of the six polycyclic aromatic hydrocarbons studied are hydrated by microsomal epoxide hydrolase with varying degrees of regioselectivity. Thus the enantiomeric composition of a metabolically formed dihydrodiol is determined by (i) the stereoselective epoxidation at a formal double bond of a parent hydrocarbon by microsomal cytochrome P-450 isozymes and (ii) the enantioselective and regioselective hydration of the metabolically formed epoxide by microsomal epoxide hydrolase.
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Affiliation(s)
- S K Yang
- Department of Pharmacology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799
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18
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Yang SK, Mushtaq M, Weems HB, Miller DW, Fu PP. Stereoselective formation and hydration of 12-methylbenz[a]anthracene 5,6-epoxide enantiomers by rat liver microsomal enzymes. Biochem J 1987; 245:191-204. [PMID: 3663145 PMCID: PMC1148099 DOI: 10.1042/bj2450191] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The K-region trans-5,6-dihydrodiols formed in the metabolism of 12-methylbenz[a]anthracene (12-MBA) by liver microsomal preparations from untreated, phenobarbital-treated and 3-methylcholanthrene-treated male Sprague-Dawley rats were found by chiral stationary-phase h.p.l.c. (c.s.p.-h.p.l.c.) analyses to contain (5S,6S)/(5R,6R) enantiomer ratios of 93:7, 88:12 and 97:3 respectively. The absolute stereochemistry of a 12-MBA trans-5,6-dihydrodiol enantiomer was elucidated by the exciton-chirality c.d. method. The 5,6-epoxides formed in the metabolism of 12-MBA by liver microsomal preparations from untreated, phenobarbital-treated and 3-methylcholanthrene-treated male Sprague-Dawley rats in the presence of the epoxide hydrolase inhibitor 3,3,3-trichloropropylene 1,2-oxide were isolated from a mixture of metabolites by normal-phase h.p.l.c., and their (5S,6R)/(5R,6S) enantiomer ratios were found by c.s.p.-h.p.l.c. analyses to be 73:27, 78:22 and 99:1 respectively. The absolute configurations of 12-MBA 5,6-epoxide enantiomers, resolved by c.s.p.-h.p.l.c., were determined via high-resolution (500 MHz) proton-n.m.r. and c.d. spectral analyses of the two isomeric methoxylation products derived from each of the 12-MBA 5,6-epoxide enantiomers. Enantiomeric pairs of the two methoxylation products were resolved by c.s.p.-h.p.l.c. The results indicate that enantiomeric 5S,6R-epoxide and 5S,6S-dihydrodiol were the major enantiomers preferentially formed in the metabolism at the K-region 5,6-double bond of 12-MBA by all three rat liver microsomal preparations. Optically pure 12-MBA 5S,6R-epoxide was hydrated predominantly at the C(6) position (R centre) to form 12-MBA trans-5,6-dihydrodiol with a (5S,6S)/(5R,6R) enantiomer ratio of 97:3. However, optically pure 12-MBA 5R,6S-epoxide was hydrated nearly equally at both C(5) and C(6) positions to form 12-MBA trans-5,6-dihydrodiol with a (5S,6S)/(5R,6R) enantiomer ratio of 57:43.
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Affiliation(s)
- S K Yang
- Department of Pharmacology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799
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Rice JE, Geddie NG, Lavoie EJ. Identification of metabolites of benzo[j]fluoranthene formed in vitro in rat liver homogenate. Chem Biol Interact 1987; 63:227-37. [PMID: 3677219 DOI: 10.1016/0009-2797(87)90043-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The metabolites of benzo[j]fluoranthene (BjF) as formed in vitro using the 9000 X g supernatant from Aroclor-pretreated rats have been identified. Two dihydrodiols, trans-4,5-dihydro-4,5-dihydroxyBjF and trans-9,10-dihydro-9,10-dihydroxyBjF have been identified as major metabolites by comparison of their spectral and chromatographic properties with those of pure synthetic standards. There was no evidence that any of the isomeric 2,3-dihydrodiol was formed as a metabolite of BjF under these incubation conditions. Neither of the metabolic dihydrodiols of BjF were formed with a high degree of stereoselectivity. The enantiomeric purity of the 4,5-dihydrodiol was 20% while that of the 9,10-dihydrodiol was 46%. At least four phenols were detected among the metabolites of BjF. These were identified as 3-, 4-, 6- and 10-hydroxyBjF based upon comparison of their UV spectra and HPLC retention times with those of synthetic reference standards. BjF-4,5-dione was also identified as a metabolite under these incubation conditions.
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Affiliation(s)
- J E Rice
- Naylor Dana Institute for Disease Prevention, American Health Foundation, Valhalla, NY 10595
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20
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Chapter 7 The Direct Preparative Resolution Of Enantiomers By Liquid Chromatography On Chiral Stationary Phases. ACTA ACUST UNITED AC 1987. [DOI: 10.1016/s0301-4770(08)60370-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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21
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Weems HB, Mushtaq M, Fu PP, Yang SK. Direct separation of non-K-region mono-ol and diol enantiomers of phenanthrene, benz[a]anthracene, and chrysene by high-performance liquid chromatography with chiral stationary phases. J Chromatogr A 1986; 371:211-25. [PMID: 3558547 DOI: 10.1016/s0021-9673(01)94706-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The direct separation of 26 bay region and non-bay region mono-ol and diol enantiomers of phenanthrene, benz[a]anthracene, and chrysene was compared by high-performance liquid chromatography on commercially available columns, packed with gamma-aminopropylsilanized silica to which either (R)-N-(3,5-dinitrobenzoyl)phenylglycine(R-DNBPG) or (S)-N-(3,5-dinitrobenzoyl)leucine(S-DNBL) was either ionically or covalently bonded. In general, enantiomers of bay region mono-ols and diols are more efficiently resolved than those of non-bay region derivatives. Elution orders of enantiomers on either chiral stationary phase are the same, regardless of whether the chiral stationary phase is ionically or covalently bonded. Except for the enantiomers of 4-hydroxy-4-methyl-1,2,3,4-tetrahydrobenz[a]anthracene, 1,2,3,4-tetrahydrobenz[a]anthracene trans-1,2-diol, and benz[a]anthracene trans-1,2-dihydrodiol, elution orders of resolved enantiomers on R-DNBPG are reversed on S-DNBL. The enantiomers are generally more efficiently resolved on R-DNBPG than on S-DNBL. With the exception of the elution order of the enantiomeric 4-hydroxy-1,2,3,4-tetrahydrochrysene, the results of this study are consistent with the chiral recognition mechanisms proposed by Pirkle and co-workers, who developed the chiral stationary phases used in this study.
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Yang SK, Mushtaq M, Fu PP. Elution order-absolute configuration relationship of K-region dihydrodiol enantiomers of benz[a]anthracene derivatives in chiral stationary phase high-performance liquid chromatography. J Chromatogr A 1986; 371:195-209. [PMID: 3558546 DOI: 10.1016/s0021-9673(01)94705-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The direct resolution of K-region cis- and trans-dihydrodiol enantiomers of 14 unsubstituted and methyl- and bromo-substituted benz[a]anthracene (BA) derivatives was investigated by high-performance liquid chromatography with commercially available columns, packed with gamma-aminopropylsilanized silica to which either (R)-N-(3,5-dinitrobenzoyl)phenylglycine (R-DNBPG) or (S)-N-(3,5-dinitrobenzoyl)leucine (S-DNBL) is either ionically or covalently bonded. BA derivatives used in this study include: BA, 1-methyl-BA, 4-methyl-BA, 7-methyl-BA, 8-methyl-BA, 10-methyl-BA, 11-methyl-BA, 12-methyl-BA, 7,12-dimethyl-BA, 7-bromo-BA, 7-bromo-1-methyl-BA, 7-bromo-11-methyl-BA, 7-bromo-12-methyl-BA, and 3-methylcholanthrene. The enantiomers of BA trans-5,6-dihydrodiol were the only compounds not resolved by any of the four chiral stationary phases (CSPs) tested. The results indicate that conformational preference of the hydroxyl group is one of the most important factor in determining the elution order of dihydrodiol enantiomers. The presence and the location of a substituent and the molecular size and shape of the dihydrodiols can significantly affect the efficiency of enantiomeric resolution. In general, the ionically bonded R-DNBPG provides the best resolution of enantiomeric quasidiequatorial trans-dihydrodiols and the R,R enantiomers are consistently more strongly retained. In contrast, the enantiomeric pairs of quasidiaxial trans-dihydrodiols are generally better resolved by the covalently bonded R-DNBPG, and the S,S enantiomers are more strongly retained. The enantiomers of cis-dihydrodiols having hydroxyl groups that adopt quasiequatorial-quasiaxial and/or quasiaxial-quasiequatorial conformations are more consistently resolved by the ionically bonded S-DNBL and in all cases the S,R enantiomers are more strongly retained. Thus, it is possible to choose a CSP which resolves the K-region dihydrodiol enantiomers with a predictable elution order.
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Hall M, Grover PL. Effects of inducers on the regio- and stereoselective metabolism of benzo[a]pyrene by mouse tissue microsomes. Chem Biol Interact 1986; 59:265-80. [PMID: 3769056 DOI: 10.1016/s0009-2797(86)80072-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The metabolism of benzo[a]pyrene (BP) by microsomal fractions of the skin, lungs and liver of the mouse, and the effects on this process of pretreatment with the xenobiotics phenobarbital (PB) and 3-methylcholanthrene (3-MC) were examined. Differences between the untreated tissues were found both in terms of the total amounts of diol recovered and in the relative proportions of the individual diols extracted following incubation. Induction with PB or 3-MC significantly altered the profiles of metabolic diols obtained with epidermal and hepatic microsomes compared with their respective controls. Pulmonary microsomes showed similar trends to those obtained with liver microsomes but these were not statistically significant. The optical purity of the BP-7,8-diol that was formed by each microsomal type was examined by direct resolution of the enantiomers on HPLC using a chiral stationary phase. In each case the (-)-7R,8R-enantiomer predominated. Pretreatment with 3-MC significantly decreased the optical purity of BP-7,8-diol recovered from incubations with skin microsomes, but significantly increased the optical purity of the diol extracted from incubations with lung and liver microsomes. In addition to the diols, an unidentified BP metabolite was found that eluted between BP-9,10- and 4,5-diol on a reverse-phase high-performance liquid chromatography (HPLC) system and which represented a major product in extracts of incubations of BP with both induced and uninduced skin and lung microsomal fractions.
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Mushtaq M, Weems HB, Yang SK. Metabolic and stereoselective formations of non-K-region benz(a)anthracene 8,9- and 10,11-epoxides. Arch Biochem Biophys 1986; 246:478-87. [PMID: 3963831 DOI: 10.1016/0003-9861(86)90494-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The non-K-region benz[a]anthracene (BA) 8,9- and 10,11-epoxides were isolated by normal-phase high-performance liquid chromatography as rat liver microsomal metabolites of BA. The identities of these epoxides were established by ultraviolet and mass spectral analyses and were further validated by the microsomal epoxide hydrolase catalyzed conversion to BA trans-8,9-dihydrodiol and trans-10,11-dihydrodiol, respectively. Circular dichroism spectral analyses of the metabolically formed non-K-region epoxides and dihydrodiols and mass spectral analyses of metabolically formed 18O-labeled non-K-region dihydrodiols and their acid-catalyzed dehydration products indicated that BA (8R,9S)-epoxide and (10S,11R)-epoxide were the predominant enantiomers formed in the metabolism at the 8,9- and 10,11- aromatic double bonds of BA, respectively, by rat liver microsomes. This is the first example demonstrating the direct detection and stereoselective metabolic formation of non-K-region epoxides of a polycyclic aromatic hydrocarbon.
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Yang SK, Mushtaq M, Weems HB, Fu PP. Chiral Recognition Mechanisms in the Direct Resolution of Diol Enantiomers of Some Polycyclic Aromatic Hydrocarbons by High Performance Liquid Chromatography with Chiral Stationary Phases. ACTA ACUST UNITED AC 1986. [DOI: 10.1080/01483918608076648] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Yang SK, Mushtaq M, Weems HB, Fu PP. Absolute configurations of enantiomeric K-region cis-5,6-dihydrodiols of 12-methylbenz[A] anthracene and 7-bromo-12-methylbenz[A] anthracene. Tetrahedron Lett 1986. [DOI: 10.1016/s0040-4039(00)85498-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Yang SK, Chiu PL. Cytochrome P-450-catalyzed stereoselective epoxidation at the K region of benz[a]anthracene and benzo[a]pyrene. Arch Biochem Biophys 1985; 240:546-52. [PMID: 3839642 DOI: 10.1016/0003-9861(85)90061-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The enantiomers of K-region benz[a]anthracene (BA) 5,6-epoxide and benzo[a]pyrene (BP) 4,5-epoxide were resolved by chiral stationary-phase high-performance liquid chromatography (CSP-HPLC). The K-region epoxides formed in the metabolism of BA by liver microsomes from untreated (control), phenobarbital (PB)-treated, and 3-methylcholanthrene (MC)-treated male Sprague-Dawley rats were determined by CSP-HPLC to have a 5R,6S/5S,6R enantiomer ratio of 25:75, 21:79, and 4:96, respectively. The K-region 4,5-epoxide formed in the metabolism of BP by the same rat liver microsomal preparations contained a 4R,5S/4S,5R enantiomer ratio of 48:52 (control), 40:60 (PB), and 5:95 (MC), respectively. The results indicate that various cytochrome P-450 isozymes of rat liver exhibit different stereoselective properties in catalyzing the epoxidation reactions at the K region of BA and of BP.
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Weems HB, Mushtaq M, Yang SK. Resolution of epoxide enantiomers of polycyclic aromatic hydrocarbons by chiral stationary-phase high-performance liquid chromatography. Anal Biochem 1985; 148:328-38. [PMID: 4061813 DOI: 10.1016/0003-2697(85)90236-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Enantiomers of nine K-region and one non-K-region epoxides of polycyclic aromatic hydrocarbons have been resolved by high-performance liquid chromatography with chiral stationary phases either ionically or covalently bonded to gamma-aminopropylsilanized silica. Resolution of enantiomers was confirmed by ultraviolet-visible absorption, circular dichroism, and mass spectral analyses. This method has been applied to the determination of optical purity and absolute configuration of the K-region epoxides formed in the metabolism of 1-methylbenz[a]anthracene, 7-methylbenz[a]anthracene, and 12-methylbenz[a]anthracene by rat liver microsomes.
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Weston A, Hodgson RM, Hewer AJ, Kuroda R, Grover PL. Comparative studies of the metabolic activation of chrysene in rodent and human skin. Chem Biol Interact 1985; 54:223-42. [PMID: 4028289 DOI: 10.1016/s0009-2797(85)80165-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Metabolism and activation of chrysene was examined in mouse, rat and human skin using a short-term organ culture technique. Mouse skin released larger quantities of free dihydrodiols into the culture medium than either rat or human skin and greater quantities of chrysene metabolites became covalently bound to the DNA of mouse skin. The stereochemistry of the chrysene-1,2-diol that was formed by each skin type was examined using high-performance liquid chromatography (HPLC) with a chiral stationary phase to resolve the enantiomers. It was found that in each case the (-)-enantiomer predominated. When hydrolysates of DNA extracted from rodent or human skin that had been treated with 3H-labelled chrysene were chromatographed on Sephadex LH-20 columns, the elution profiles of the hydrocarbon-DNA adducts were found to vary between the species studied. Further examination using HPLC showed that some of the adducts formed in skin had the chromatographic characteristics of adducts formed when the anti-isomer of the 'bay-region' diol-epoxide of chrysene (r-1,t-2-dihydroxy-t-3,4-oxy-1,2,3,4-tetrahydrochrysene) reacted with DNA and that others had the characteristics of triol-epoxide adducts.
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Chou MW. Application of chiral high performance liquid chromatography to the separation of structurally similar nitro-polycyclic aromatic hydrocarbons. ACTA ACUST UNITED AC 1985. [DOI: 10.1002/jhrc.1240080609] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Chiu PL, Fu PP, Weems HB, Yang SK. Absolute configuration of trans-7,8-dihydroxy-7,8-dihydro-7-methylbenzo[a]pyrene enantiomer and the unusual quasidiequatorial conformation of the diacetate and dimenthoxyacetate derivatives. Chem Biol Interact 1985; 52:265-77. [PMID: 3971469 DOI: 10.1016/0009-2797(85)90022-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The enantiomers of trans-7,8-dihydroxy-7,8-dihydro-7-methylbenzo[a]pyrene (7-MBaP 7,8-dihydrodiol) and of trans-7,8-dihydroxy-7,8,9,10-tetrahydro-7-methylbenzo[a]pyrene (7-MBaP 7,8-tetrahydrodiol) were directly resolved by high-performance liquid chromatography (HPLC) using a commercially available column packed with an (R)-N-(3,5-dinitrobenzoyl)-phenylglycine derivative of gamma-aminopropylsilanized silica. The absolute configurations of the resolved enantiomers were determined by the exciton chirality method. Circular dichroism (CD) spectral analysis of the quasidiequatorial benzo[a]pyrene 7R,8R-dihydrodiol enantiomer and its diacetate and dimenthoxyacetate derivatives indicated conformational changes were induced upon derivatization. However, the characteristic CD Cotton effects of the quasidiequatorial 7-MBaP 7,8-dihydrodiol and its diacetate and dimenthoxyacetate derivatives were similar indicating that the conformation of 7-MBaP trans-7,8-dihydrodiol was not altered upon derivatization. Proton nuclear magnetic resonance (NMR) spectral analyses confirmed that 7-MBaP 7,8-dihydrodiol, its diacetate and dimenthoxyacetate derivatives all have quasidiequatorial conformations. The results indicate that the methyl substituent of 7-MBaP 7,8-dihydrodiol maintains a quasiaxial position regardless of the size of the acyl derivatives linked to the hydroxyl groups.
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Yang SK, Fu PP. The effect of the bay-region 12-methyl group on the stereoselective metabolism at the K-region of 7,12-dimethylbenz[a]anthracene by rat liver microsomes. Biochem J 1984; 223:775-82. [PMID: 6439187 PMCID: PMC1144362 DOI: 10.1042/bj2230775] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The enantiomers of a trans-5,6-dihydrodiol formed in the metabolism of 7,12-dimethylbenz[a]anthracene by rat liver microsomes (microsomal fractions) were resolved by chiral stationary-phase high-performance liquid chromatography. The major 7,12-dimethylbenz[a]anthracene trans-5,6-dihydrodiol enantiomer and its hydrogenation product 5,6,8,9,10,11-hexahydro-trans-5,6-diol were found to have 5S,6S absolute configurations by the exciton chirality c.d. method. The R,R/S,S enantiomer ratios of 7,12-dimethylbenz[a]anthracene trans-5,6-dihydrodiol formed in the metabolism of 7,12-dimethylbenz[a]anthracene by liver microsomes from untreated, 3-methylcholanthrene-treated and phenobarbital-treated male Sprague-Dawley rats were found to be 11:89, 6:94, and 5:95 respectively. These findings and those reported previously on the metabolic formations of trans-5,6-dihydrodiols from 7-methylbenz[a]anthracene and 12-methylbenz[a]anthracene suggest that the 12-methyl group in 7,12-dimethylbenz[a]anthracene plays an important role in determining the stereoselective metabolism at the K-region 5,6-double bond. Furthermore, the finding that formation of 5S,6S-dihydrodiol as the predominant enantiomer was not significantly affected by the isoenzymic composition of cytochrome P-450 present in microsomes prepared from the livers of the rats pretreated with the different inducing agents indicates that the stereoselectivity depends on the substrate metabolized rather than on the precise nature of the metabolizing-enzyme system.
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Chiu PL, Mushtaq M, Weems HB, Yang SK. Stereoselective hydroxylation at the aliphatic carbons of 7,8- and 9,10-dihydrobenzo[a]pyrenes by rat liver microsomes. Biochem Biophys Res Commun 1984; 124:114-20. [PMID: 6497875 DOI: 10.1016/0006-291x(84)90924-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Optically active 7-hydroxy-7,8-dihydrobenzo[a]pyrene and 8-hydroxy-7,8-dihydrobenzo[a]pyrene were identified as two of the major metabolites formed by incubation of 7,8-dihydrobenzo[a]pyrene with rat liver microsomes. Optically active 9-hydroxy-9,10-dihydrobenzo[a]pyrene and 10-hydroxy-9,10-dihydrobenzo[a]pyrene were similarly identified as two of the minor metabolites of 9,10-dihydrobenzo[a]pyrene. The formation of these metabolites was abolished either by prior treatment of liver microsomes with carbon monoxide or the absence of NADPH, but was not inhibited by an epoxide hydrolase inhibitor. The results indicate that the aliphatic carbons of dihydro polycyclic aromatic hydrocarbons may undergo stereoselective hydroxylation reactions catalyzed by the cytochrome P-450 system of rat liver microsomes.
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Yang SK, Li XC. Direct enantiomeric resolution of cyclic alcohol derivatives of polycyclic aromatic hydrocarbons by chiral stationary phase high-performance liquid chromatography. J Chromatogr A 1984; 291:265-73. [PMID: 6330139 DOI: 10.1016/s0021-9673(00)95028-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The enantiomers of some cyclic alcohol derivatives of phenanthrene, benz[a]anthracene, benzo[a]pyrene, cholanthrene, and 3-methylcholanthrene were resolved by high-performance liquid chromatography using a commercially available preparative column packed with an (R)-N-(3,5-dinitrobenzoyl)phenylglycine ionically bonded to gamma-aminopropylsilanized silica. Resolution of enantiomers was confirmed by ultraviolet-visible absorption, mass and circular dichroism spectral analyses. This method has been applied to the determination of optical purity of 1-hydroxycholanthrene and 1-hydroxy-3-methylcholanthrene formed in the metabolism of cholanthrene and 3-methylcholanthrene, respectively, by rat liver microsomes.
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Yang SK, Weems HB, Mushtaq M, Fu PP. Direct resolution of mono- and diol enantiomers of unsubstituted and methyl-substituted benz[a]anthracene and benzo[a]pyrene by high-performance liquid chromatography with a chiral stationary phase. J Chromatogr A 1984; 316:569-84. [PMID: 6549394 DOI: 10.1016/s0021-9673(00)96184-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The direct resolution of 86 structurally related monomethyl, mono-ol, and trans- and cis-diol enantiomers of unsubstituted and methyl-substituted benz[a]anthracene and benzo[a]pyrene was investigated by high-performance liquid chromatography with a commercially available column, packed with an (R)-N-(3,5-dinitrobenzoyl)phenylglycine, ionically bonded to gamma-aminopropylsilanized silica. The results indicate that structural factors, such as conformation, presence of a methyl substituent, molecular size and shape, and ring saturation all contribute to chiral interactions between the chiral stationary phase and the solutes. Detailed chiral recognition mechanisms can not yet be established, due to complex structural factors that influence enantiomeric resolutions and the lack of data on the absolute configurations of the resolved enantiomers. Nevertheless, the chromatographic method can be applied to the determination of enantiomeric purity of mono- and diol metabolites of polycyclic aromatic hydrocarbons. The absolute configurations of a limited number of resolved enantiomers have been established.
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Pirkle WH, Myung HH, Bank B. A rational approach to the design of highly-effective chiral stationary phases. J Chromatogr A 1984. [DOI: 10.1016/s0021-9673(00)96185-5] [Citation(s) in RCA: 126] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Fu PP, Yang SK. Stereoselective metabolism of 6-bromobenzo[a]pyrene by rat liver microsomes: absolute configuration of trans-dihydrodiol metabolites. Biochem Biophys Res Commun 1982; 109:927-34. [PMID: 7159450 DOI: 10.1016/0006-291x(82)92029-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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