Superoxide anion and alpha, alpha-diphenyl-beta-picrylhydrazyl radical scavenging capacity of rooibos (Aspalathus linearis) aqueous extracts, crude phenolic fractions, tannin and flavonoids
2004
Joubert, E. | Winterton, P. | Britz, T.J. | Ferreira, D.
Rooibos flavonoids and tannin, as well as aqueous extracts and crude phenolic fractions of unfermented and fermented rooibos (Aspalathus linearis) were evaluated for their capacity to scavenge alpha, alpha-diphenyl-beta,-picrylhydrazyl (DPPH·) and superoxide anion (O2-·) radicals. The relative potency of rooibos flavonoids towards DPPH· decreased in the order: quercetin greater than or equal to procyanidin B3 greater than or equal to orientin greater than or equal to luteolin greater than or equal to aspalathin approximately equal to isoquercitrin > iso-orientin catechin > rutin >> vitexin greater than or equal to chrysoeriol. A different order was obtained for O2-·: quercetin approximately equal to aspalathin > orientin greater than or equal to catechin greater than or equal to rutin greater than or equal to isoquercitrin > iso-orientin > luteolin > chrysoeriol > vitexin. Aspalathin was more effective than Trolox, the water-soluble analogue of α-tocopherol. Ethyl acetate solubles of the aqueous extract of unfermented rooibos and the crude aspalathin fraction, with the highest total polyphenol and aspalathin contents, had the greatest anti-radical capacity. Rooibos tannin, lowest in total polyphenol content, was the least effective radical scavenger. Fermentation decreased the anti-radical capacity of the aqueous extracts and crude phenolic fractions.
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