Identification of hydroxyhydroquinone in coffee as a generator of reactive oxygen species that break DNA single strands.

A component in instant coffee that caused DNA single strand breaks was isolated by successive ethyl acetate:ethanol extraction, silica gel column chromatography and high performance liquid chromatography using a reversed phase column. The active component was identified as hydroxyhydroquinone (HHQ). Incubation of supercoiled pBR 322 DNA with HHQ at 0.1 mM in phosphate buffer (pH 7.4) at 37 degreesC for 1 h caused single strand breaks, and reactive oxygen species, hydrogen peroxide and hydroxyl radical, were involved in DNA breaking by HHQ. Genotoxic effects of HHQ including DNA breaking activity through generation of reactive oxygen species have been well-demonstrated because the component is considered to be an important genotoxic intermediate metabolite of benzene. Occurrence of HHQ in coffee must have an important significance to consider genotoxicity of coffee.