Scirpusin A,a hydroxystilbene dimer from Xinjiang wine grape,acts as an effective singlet oxygen quencher and DNA damage protector

BACKGROUND: Grapes and red wines are rich sources of phenolic compounds such as anthocyanins, catechins, flavonols and stilbenes, most of which are potent antioxidants showing cardioprotective properties. We first isolated scirpusin A, a hydroxystilbene dimer, from a wine grape of Xinjiang, and studied its antioxidant activity. RESULTS: Reactive oxygen species scavenging effects and the protection against reactive singlet oxygen‐induced DNA damage of scirpusin A have been investigated in our experiments. The concentration of scirpusin A required to inhibit 50% of ¹O₂ generation was 17 µmol L^?1, while addition of scirpusin A at 140 µmol L^?1 caused complete inhibition. Further kinetic study revealed that the reaction of Scirpusin A with singlet oxygen has an extremely high rate constant (k_a = 4.68 × 10⁹ L mol^?1 s^?1). Scirpusin A (140 µmol L^?1) exhibited significant inhibition effects on pBR322 DNA breakage. However, scavenging effects of scirpusin A on superoxide anion O₂^?? and hydroxyl radical ·OH were not potent as the inhibitor rates at a concentration of 1400 µmol L^?1 were 28.83% and 19.5%, respectively. CONCLUSION: The present study shows that scirpusin A is a selective quencher of singlet oxygen and a protector against reactive singlet oxygen‐induced pBR322 DNA damage at very low concentrations. Copyright © 2010 Society of Chemical Industry