Rapid identification of the antioxidant constituent of Koelreuteria henryi

In recent years, on-line coupling of separation and activity determination techniques has been achieved by mixing a free radical solution with the eluate of an HPLC column. Such techniques enable the rapid and selective detection of radical scavenging substances in the sample preparation. This study investigates the antioxidant properties of the leaves of Koelreuteria henryi L. using a microarray reader and HPLC. The antioxidant, 1,3,4,5-tetra-O-galloylquinic acid (1), was first isolated from this plant and estimated using LC-MS/MS and NMR methods. The scavenger activity of (1) was then determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and xanthine oxidase (XOD) assays, producing an IC₅₀ of 7.1 μM and 6.7 μM, respectively. Results show that this compound has an excellent antioxidant effect in comparison with quercetin. This study shows that it is possible to rapidly identify the antioxidant constituents of K. henryi L. using the hyphenated DPPH (or XOD) assays and LC-MS/MS methods.