Microbial transformation of 6‐nitrobenzo[a]pyrene

Abstract

The fungal metabolism of the potent mutagenic and carcinogenic nitropolycyclic aromatic hydrocarbon (nitro‐PAH) 6‐nitrobenzo[a]pyrene (6‐NO ₂ ‐BaP) was investigated. Cunninghamella elegans was incubated with 6‐NO ₂ ‐BaP for periods ranging between 1 and 7 d, and the metabolites formed were separated by high‐performance liquid chromatography and identified by their UV‐visible absorption, mass, and ¹ H nuclear magnetic resonance spectra. The results of our study indicate that C. elegans metabolized 6‐NO ₂ ‐BaP to glucoside and sulfate conjugates of 1‐ and 3‐hydroxy 6‐NO ₂ ‐BaP and suggests that glycosylation and sulfation reactions may represent detoxification pathways in the fungal metabolism of nitro‐PAHs. Experiments using [C‐ ³ H]‐6‐NO ₂ ‐BaP indicated that C. elegans metabolized 62% of 6‐NO ₂ ‐BaP within 768 h. Our data also indicated that the nitro group at the C‐6 position of benzo[a]pyrene blocked metabolism at the regions peri to the nitro substituent (C‐7, C‐8 positions) and enhanced metabolism at the C‐l and C‐3 positions. The ability of the fungus C. elegans to metabolize 6‐NO ₂ ‐BaP to biologically inactive compounds may have practical applications in the detoxification of nitro‐PAH‐contaminated wastes.