The effect of a peripheral disulfide bridge substituent on the phenolic O-H bond dissociation energy (BDE) and the ionization potential (IP) of naphthyridine diol has been studied by density functional theory (DFT) calculation. Compared with naphthalene diol, the substituent of a peripheral disulfide bridge group is very efficient in reducing the BDE, whereas the insertion of nitrogen atoms into the naphthalenic ring only slightly changes the BDE of O-H bond but dramatically enhances the IP. It is similar with the stereoelectronic effect of the heterocyclic ring for the well-known alpha-tocopherol antioxidant and leads to a highly delocalized spin distribution. With the incorporation of these two aspects, a potential antioxidant is expected to be more active and more stable than alpha-tocopherol.