Kinetic study of Sasa veitchii extract as a radical scavenger and an antioxidant.

We examined the free radical scavenging activity of Sasa veitchii extract (Hoshi's Striped Bamboo Extract(®), HSBE), well known in folk medicine as an efficient drug and antioxidant in detail. To evaluate the free radical scavenging activity of HSBE, its reactivity as hydrogen atom donor toward the 1, 1-diphenyl-2-picrylhydrazyl has been measured using stopped-flow spectrophotometry. It was found that the second-order rate constant, k(2), obtained at 25 °C was 1.4 (g/L)(-1) s(-1) for HSBE. To compare different chain-breaking antioxidants quantitatively, we obtained the second-order rate constant, k(2)', on the molar basis of active hydroxyl groups in the tested substances. As a result, the k(2)' values for HSBE, 6-hydroxy-2, 5, 7, 8-tetramethylchroman-2-carboxylic acid (Trolox), caffeic acid, and (+)-catechin were 2.6 × 10(3), 2.0 × 10(3), 2.3 × 10(2), and 6.0 × 10(2) M(-1) s(-1), respectively. These results show that HSBE and Trolox exerted the same free radical scavenging activity under these conditions. In addition, HSBE significantly inhibited the oxidation of methyl linoleate micelles in aqueous dispersions at 30 °C and its antioxidant activity (k(inh)) was more effective than those of caffeic acid and (+)-catechin. This is the first study on bamboo extracts in the context of radical scavenging activity that reports kinetic results. We determined the stoichiometric number and the rate constants of bamboo extracts using the method that was devised in determining the antioxidant activity of mixtures. This is the first study of bamboo extracts as an antioxidant that reports the stoichiometric and kinetic results.