Formation of new heterocyclic amine mutagens by heating creatinine, alanine, threonine and glucose

Abstract

A mixture of alanine, threonine, creatinine and glucose was heated in diethylene glycol and water (5:1, v/v) for 15 min at 200 degrees C. The mutagens formed were purified by high-performance liquid chromatography using the Ames/Salmonella mutagenic activity to guide the purification. The structures of the purified mutagens were determined using UV absorption, mass and NMR spectrometry. A new mutagenic compound with a mass number of 217 was found and its mass spectrum did not correspond to any known mutagen derived from food. This new compound accounted for 4% of the total mutagenic activity. Other mutagenic compounds were identified as MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline), 4,8-DiMeIQx (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline), and a new mutagen 4,7,8-TriMeIQx (2-amino-3,4,7,8-tetramethylimidazo[4,5-f]quinoxaline) with a mutagenic activity of 73,000 TA98 revertants per microgram. The percentage of the mutagenic activity attributable to MeIQx, 4,8-DiMeIQx and 4,7,8-TriMeIQx was 10%, 70% and 3%, respectively. The yield of MeIQx, 4,8-DiMeIQx and 4,7,8-TriMeIQx was 10, 36 and 6 nmole/mmole creatinine. The formation of TriMeIQx from natural meat components suggests that this new quinoxaline mutagen may be present in cooked foods.