Mechanistic processes of resveratrol in inhibiting the oxidative damage of guanine, as evidenced by UHPLC-MS2

Resveratrol, as one of the stilbenoids, is present in abundance in wine grapes and has been shown to selectively quench 1O2. DNA is oxidized by 1O2 causing irreparable functional damage, and of the nucleic acids, guanine is the most susceptible. An agarose gel electrophoresis assay demonstrated that DNA was damaged by 1O2 with less than 5 min of UVA irradiation, and also that 5 mM resveratrol dissolved in MeOH could relieve the observed oxidation stress. Ultra-high performance liquid chromatography coupled with mass spectrometry was performed to reveal the mechanism. Four guanine oxidation products at m/z 140.0334 [M-H]− (1), DGh, 8-oxoG, Sp and two conjugates at m/z 377.1104 [M-H]− and 391.0907 [M-H]− were identified and quantified. Thus, we propose the mechanism that the phenol ring of resveratrol links with the free amino groups (NH) of guanine at the beginning of 1O2 attack to form m/z 377.1104 [M-H]−, however, as 1O2 is able to attack the amino groups continuously, resveratrol can efficiently react with 1O2 prior to damage, and form m/z 391.0907 [M-H]− thereby protecting guanine.