Abstract: Chemiluminescence (CL) was observed during the oxidation of Luminol (2 mg/L), mediated by 0.06% hydrogen peroxide (H2O2) and cytochrome c (10 mg/L), CL intensity was decreased by the presence of radical scavengers and the reduction was linearly proportional to the concentration and ability of scavengers; butylated hydroxytoluene (BHT), caffeic acid and gallic acid, The order of effectiveness as radical scavengers was gallic acid > caffeic acid > BHT, which shows that the number of hydroxyl groups (OH) in the B-ring of flavonoids plays a key role in a good radical scavenging activity, Of eight catechins obtained from green tea extracts, (-)-catechin was the least effective and (-)-epigallocatechin gallate (EGCg) showed the strongest activity. This result indicates that the stereoscopic structure between the C-3 group and the B ring of flavonoids as well as substituents at the C-3 position make a contribution to radical scavenging activity. Of the tested Chinese herbal ingredients, five species of ingredients represented more than 90% of the radical scavenging activity. Copyright

Abstract: The authors report a simple, rapid and reproducible flow injection-chemiluminescent method for radical scavenging activity. Chemiluminescence intensity is decreased by the presence of scavengers and the reduction is proportional to the concentration. and ability of scavengers. The flow injection-chemiluminescent method represents high reproducibility and anal. speed. The authors achieved relative standard deviation of 1.88%, and each run in less than 25 s. The present technique proves to be inexpensive, fast, and reliable. This flow injection-chemiluminescent technique could be applied as an alternative method for the measurement of the radical scavenging abilities of biological components. (c) 1998 Academic Press.