Results and discussion
HQs are thermodynamically less stable at neutral pH than the corresponding quinones (Qs) [15]. In a buffered aqueous solution, HQ is slowly oxidized to BQ via a semiquinone (SQ) radical The same is true for HQ by a Cu(II)-mediated oxidation to corresponding SQ radicals which are then oxidized to p-benzoquinone [4] leading to DNA damage according to following mechanism