Concordance between antioxidant activities in vitro and chemical components of Radix Astragali (Huangqi).

ABSTRACT

Five Radix Astragali (RA) extracts were prepared and their antioxidant activities were measured in vitro using ABTS [2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid diammonium salt)], DPPH · (1,1-diphenyl-2-picrylhydrazyl radical), reducing power, •O2⁻ and •OH assays. Their chemical contents were then determined, including total phenolics, total flavonoids, total saponins and total sugars. The 1/IC50 values of the various antioxidant assays were used to evaluate the level of antioxidant activity of the RA extracts (plot showing 1/IC50 values vs. chemical contents), and the average R values (correlation coefficients) of total phenolics and total flavonoids were 0.762 and 0.638. In contrast, the average R values of the total saponins and total sugars were -0.0386 and -0.132, respectively. This large difference clearly demonstrates that the antioxidant effects of RA in vitro might be generally considered to be a result of the presence of phenolic compounds (including flavonoids) but not astragalosides and polysaccharides.