In vitro synergistic anti-oxidant activities of solvent-extracted fractions from Astragalus membranaceus and Glycyrrhiza uralensis

Our study estimated the in vitro anti-oxidant activities of the solvent-extracted fractions from Astragalus membranaceus (AME), Glycyrrhiza uralensis (GU) and the combination of them (AG), using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging assay and ferric reducing anti-oxidant power (FRAP) assay. Different solvent extracts have different anti-oxidant activities. As to the herb pair (AG), the highest anti-oxidant capacity and total phenolic/flavonoid content were observed in the ethyl acetate fraction, which were exhibited in different solvent fractions of the individual herbs. The ethyl acetate extract of herb pair (EA-AG) showed significantly higher anti-oxidant capacity than the theoretical sum of two single herbs, and presented better cytoprotection and induced higher activity of anti-oxidant enzymes than the single herbs. Moreover, there's a linear correlation between the increment of total phenolics/flavonoids and anti-oxidant capacities, especially between polyphenol content and TEAC values (correlation coefficient = 0.9∗). These indicated that the phenolic and flavonoid may be the main compounds which caused the synergistic anti-oxidant capacity and cytoprotection in the combination of AME and GU.