Intramolecular Base-Accelerated Radical-Scavenging Reaction by Vitamin E Derivatives Bearing a Pyridine Moiety

Fine-tuning of the radical-scavenging activity of antioxidants is of considerable importance with regard to the development of effective chemopreventive agents against oxidative stress and associated diseases. We have reported that the scavenging reaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical by 2,2,5,7,8-pentamethylchroman-6-ol (PMC), a vitamin E model, proceeds via a proton-coupled electron transfer in deaerated methanol (MeOH) and that pyridines significantly accelerate this reaction by stabilizing a radical cation intermediate derived from PMC. In this study, we synthesized three vitamin E derivatives bearing a pyridine moiety with a linkage of different spacers. All the vitamin E derivatives thus obtained efficiently scavenged DPPH radical in deaerated MeOH. The second-order rate constant for the scavenging of DPPH radical by one of the vitamin E derivatives determined by the stopped-flow technique is about 3-fold larger than that by PMC. The scavenging activity of DPPH radical is found to be depending on the length of the spacers.Oxygen Club of California (OCC) 2010 World Congres