Dihydropyrazines (DHPs), which generate hydroxyl and carbon-centered radicals, cleaved DNA single-strand. It is new knowledge that DHPs were recently determined to produce 8-hydroxydeoxyguanosine. The remarkable increase in the DNA strand-cleavage activity upon the addition of Cu2+ suggests that the primary reactive species is carbon-centered radicals rather than the hydroxyl radical generated the initiation reaction. This proposal was in fair agreement with of the observed carbon-centered radical signal intensity, but an effect was not observed with the increase in the hydroxyl radical signal intensity.