Chem. Pharm. Bull. 53(6) 714—716 (2005)

tion, stable radicals have the advantage that their concentrations are readily and directly measurable. Among them a stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) was investigated as a reactive hydrogen acceptor and further found to be useful for the antioxidant determination. Since then DPPH has been mainly used to examine radical scavenging activity of antioxidative vitamins and polyhydroxy aromatic compounds based on the reactions in Fig. 1. Besides DPPH-scavenging by reductive hydrogen transfer between various donors and DPPH, non-reductive DPPH-decomposing and -scavenging were found to be induced by reacting with tertiary hydroperoxides and by radical-binding at the para position in the phenyl rings of DPPH, respectively. However, nowadays non-reductive DPPH-scavenging has hardly applied for biochemical and physicochemical purposes. It has been reported that peroxyradicals are unique among reactive oxygen species implicated in the production of DNA damage because they possess an extremely long half-life (order of seconds) and are predicted to have a relatively greater chemical selectivity in its reactions as compared with other radical intermediates. Several methods have developed for the determination of peroxyradicals such 714 Notes Chem. Pharm. Bull. 53(6) 714—716 (2005) Vol. 53, No. 6