Enhancement of radical intensity and cytotoxic activity of ascorbate by PSK and lignins.

ESR spectroscopy revealed that high molecular weight natural substances, such as protein-bound polysaccharide PSK, alkali-lignin and lignin sulfonate, significantly enhanced the ascorbyl radical intensity derived from sodium ascorbate or ascorbic acid in culture medium. Enhancement of the ascorbyl radical intensity was coupled with rapid degradation of ascorbate. These substances synergistically enhanced the ascorbate-induced cytotoxicity against human leukemic and glioblastoma cell lines. These data suggest the possible role of the ascorbyl radical in cytotoxicity induction.