Isolation and identification of a new mutagen, 2-amino-4-hydroxy-methyl-3, 8-dimethylimidazo[4,5-f] quinoxaline (4-CH2OH-8-MeIQx), from beef extract

By monitoring the mutagenicity to a new Salmonella tester strain,YG1024, which has a much higher level of 0- acetyltransferaseactivity than S.typhimurium TA98, we found two new mutageniccompounds in bacteriological-grade beef extract. One of them(compound I), which had a similar UV spectrum to that of 2-amlno-3,4,8-trimethylimidazo4,5-f]quinoxaline (4,8-DiMeIQx), was isolated and shown toaccount for {small tilde}2% of the total mutagenicity of thematerials adsorbed to blue cotton, and its concentration wasestimated to be 6.0 ng/g beef extract. This amount of compoundin beef extract was insufficient to allow measurements of variousspectra, but its level was increased {small tilde}9-fold byheating beef extract with creatine and threonine at 200°Cfor 5 h. From UV and mass spectra of the compound obtained frombeef extract heated with creatine plus threonine, it was deducedto be a hydroxymethyl derivative of anminodimethylimidazoquinoxaline.Compound I was isolated from the urine of rats given 4,8-DiMeIQxand identified as 2-amino-4-hydroxymethyl-3,8-dimethylimidazo4,5-f]quinoxaline (4-CH₂OH-8-MeIQx) by ¹H-NMR analysis. 4-CH²OH-8-MeIQxinduced 326 000 revertants of YG1024 and 99 000 revertants ofTA98 per µg in the presence of S9 mix.