Biol. Pharm. Bull. 30(9) 1663—1667 (2007)

of dihydropyrazines (DHPs) such as 2,3-dihydro-5,6-dimethylpyrazine (Me-DHP), which causes DNA strand breakage in the plasmid pBR322. We showed that DHPs inhibit growth and cause mutagenesis in Escherichia coli and that Me-DHP is cytotoxic and genotoxic in E. coli due to the production of radical species in the presence of Cu . Phenyl substituted dihydropyrazines (Ph-DHPs) have much higher DNA strand-breaking activity and produce higher levels of radical species than Me-DHP. Therefore, in the current studies, we examined the effects of Ph-DHPs on E. coli. It is forecast that DHP that originates in the sugar is in vivo generated, and exists universally in vivo, and has revealed a critical role by the characteristics as mentioned before. These DHPs may be involved in various internal injuries in vivo, the characteristics of DHPs in vivo may be significant in the prevention of disease. It was already reported that a dihydropyrazine (DHP) derivative, 3,6-dihydropyrazine-2,5-dipropanoic acid, derived from 5-aminolevulinic acid, caused the increased frequency of liver cancer by DNA damage.