Comparative Study of 1,1-Diphenyl-2-picryl-hydrazyl Radical (DPPH•) Scavenging Capacity of the Antioxidant Xanthones Family

This study compares the antioxidant capacities of the xanthone family and analyzes structure-activity relationship. Thirty xanthones with various structural features were selected as the references and their antioxidant capacities were determined using the 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH center dot) scavenging assay. The results of the assay indicated that these xanthones could scavenge the DPPH center dot in a dose-dependent manner. It was found that their Trolox equivalent antioxidant capacity (TEAC) values varied by the presence or absence of hydroquinone (or catechol) group within the molecule. The former 15 xanthones (1-15, TEAC=2.030-0.568) with hydroquinone (or catechol) pattern possessed much higher TEAC values than the latter 15 xanthones (16-30, TEAC=0.019-0.002) without hydroquinone (or catechol) pattern. It was concluded that the presence of the hydroquinone (or catechol) group governs the antioxidant capacity of xanthone family. Other structural factors, such as isoprenylation, methylation, and glycosidation, play a minor role, unless they remove the hydroquinone (or catechol) pattern. These findings can be used to directly predict the antioxidant capacity of xanthone.