title: Stereoselective fungal metabolism of 7,12-dimethylbenz[a]anthracene: identification and enantiomeric resolution of a K-region dihydrodiol.
abstract: Syncephalastrum racemosum UT-70 and Cunninghamella elegans ATCC 36112 metabolized 7,12-dimethylbenz[a]anthracene (7,12-DMBA) to hydroxymethyl metabolites as well as 7-hydroxymethyl-12-methylbenz[a]anthracene trans-3,4-, -5,6-, -8,9-, and -10,11-dihydrodiols. The 7,12-DMBA metabolites were isolated by reversed-phase high-performance liquid chromatography and identified by their UV-visible absorption, mass, and nuclear magnetic resonance spectral characteristics. A comparison of the circular dichroism spectra of the K-region (5,6-position) dihydrodiol of both fungal strains with those of the 7,12-DMBA 5S,6S-dihydrodiol formed from 7,12-DMBA by rat liver microsomes indicated that the major enantiomer of the 7-hydroxymethyl-12-methylbenz[a]anthracene trans-5,6-dihydrodiol formed by both fungal strains had a 5R,6R absolute stereochemistry. Direct resolution of the fungal trans-5,6-dihydrodiols by chiral stationary-phase high-performance liquid chromatography indicated that the ratios of the R,R and S,S enantiomers were 88:12 and 77:23 for S. racemosum and C. elegans, respectively. These results indicate that the fungal metabolism of 7,12-DMBA at the K region (5,6-position) is highly stereoselective and different from that reported for mammalian enzyme systems.
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000378:metabolism*; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid; D009682:Magnetic Resonance Spectroscopy; D008862:Microsomes, Liver / Q000201:enzymology; D009090:Mucorales / Q000378:metabolism*; D051381:Rats; D013237:Stereoisomerism
chemical_list: D015127:9,10-Dimethyl-1,2-benzanthracene