Application of novel assay methods for superoxide anion-scavenging activity to food samples [Japanese]

摘要

Recently, the authors developed novel assay methods of superoxide dismutase, WST-1 method and chemiluminometric FIA (CL-FIA) method. In the present investigation, those two methods were applied to estimate superoxide anion-scavenging activity (SOSA) of foods and the results were compared with those by ESR method. Red wine, green tea, cocoa and coffee were used as the sample. The first one is the colorimetric method using highly water-soluble tetrazolium salt (WST-1). The dilution ratio giving 50% inhibition (IC50) of each sample by the WST-1 method was as follows : red wine, X 180-230 : green tea, X 3000; cocoa, X 230; coffee, X 210. Although direct reduction of WST-1 with food components was observed without involvement of superoxide anion, the extent of the non-specific reduction was less than 3% in those dilution ratios. The second one is the CL-FIA method using chemiluminescence of lucigenin. The immobilized xanthine oxidase in a reactor was used to generate superoxide anion. This method could be a useful tool for measuring SOSA (60 samples/h) much more rapidly in comparison with the other conventional methods. The following IC50 was obtained : red wine, X 3800-5800; green tea, X 120000-150000; cocoa, X 4300 : coffee, X 4100. The non-specific chemiluminescence was not observed in these dilution ratios. Furthermore, this system showed high stability even during 250 repetitive injections of diluted food samples. A significant linear relationship between these novel methods and the ESR method was recognized, indicating that these methods might be applicable to estimate SOSA of foods.