Structural identification of the major DNA adduct formed by aflatoxin B1 in vitro

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 74; no. 5; pp. 1870 - 1874
• Main Authors: J M Essigmann, R G Croy, A M Nadzan, W F Busby, Jr, V N Reinhold, G Büchi, G N Wogan
• Format: Journal Article
• Language: English
• Published: United States National Acad Sciences 01-05-1977
• Subjects: Aflatoxins - metabolism; Animals; Chromatography, High Pressure Liquid; DNA - metabolism; Guanine - metabolism; Magnetic Resonance Spectroscopy; Male; Microsomes, Liver - metabolism; Rats; Spectrophotometry, Ultraviolet
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.74.5.1870

The covalent binding of the hepatocarcinogen aflatoxin B1 by rat liver microsomes to calf thymus DNA resulted in a binding level equal to one aflatoxin residue per 60 DNA nucleotides. An aflatoxin derivative-guanine adduct was efficiently liberated from DNA with formic acid. Analytical reversed-phase high-pressure liquid chromatography of the DNA hydrolysate revealed that approximately 90% of the carcinogen bound to DNA could be accounted for as a single component. Preparative high-pressure liquid chromatography was used to isolate sufficient quantities of the adduct for structural analysis from large quantities (340 mg) of DNA. A combination of spectral and chemical data indicates that the major product of the interaction of metabolically activated aflatoxin B1 and DNA is 2,3-dihydro-2-(N7-guanyl)-3-hydroxyaflatoxin B1 with the guanine and hydroxyl functions possessing a trans configuration. The structural data support the hypothesis that the putative 2,3-oxide of aflatoxin B1 is quantitatively important as an intermediate in the binding of aflatoxin B1 to nucleic acids.