Interaction between sodium 5,6-benzylidene-L-ascorbate and gallic acid

The interaction between sodium 5,6-benzylinene-L-ascorbate (SBA) and gallic acid was investigated by two different parameters: radical intensity and c ytotoxicity induction. These compounds produced ESR signals of radicals und er alkaline conditions. The addition of increasing concentrations of SEA co mpletely scavenged the gallate radical and replaced the latter with its asc orbate radical. On the other hand, gallic acid dose-dependently enhanced th e radical intensity of SEA. Both of these two compounds dose-dependently re duced the viable cell number of human squamous carcinoma HSC-2 cells withou t inducing internucleosomal DNA cleavage. Electron micrographs of the dying cells demonstrate the irreversible degenerative changes especially in the cytoplasm of the cells. The cytotoxic activity of gallic acid was almost co mpletely eliminated by catalase, whereas SEA was totally insensitive to cat alase. When these two compounds were mixed together before adding to HSC-2 cells, the cytotoxic activity of gallic acid was significantly reduced by S EA, whereas that of SEA was not reduced by gallic acid. SEA dose-dependentl y reduced the gallate oxidation in the culture medium. The interaction betw een SEA and gallic acid may modify their individual biological activity.