Antioxidant activity applying an improved ABTS radical cation decolorization assay

A method for the screening of antioxidant activity is reported as a decolor ization assay applicable to both lipophilic and hydrophilic antioxidants, i ncluding flavonoids, hydroxycinnamates, carotenoids, and plasma antioxidant s. The pre-formed radical monocation of 2,2'-azinobis-(3-ethylbenzothiazoli ne-6-sulfonic acid) (ABTS(.+)) is generated by oxidation of ABTS with potas sium persulfate and is reduced in the presence of such hydrogen-donating an tioxidants. The influences of both the concentration of antioxidant and dur ation of reaction on the inhibition of the radical cation absorption are ta ken into account when determining the antioxidant activity. This assay clea rly improves the original TEAC assay (the ferryl myoglobin/ABTS assay) for the determination of antioxidant activity in a number of ways. First, the c hemistry involves the direct generation of the ABTS radical monocation with no involvement of an intermediary radical. Second, it is a decolorization assay; thus the radical cation is pre-formed prior to addition of antioxida nt test systems, rather than the generation of the radical takings place co ntinually in the presence of the antioxidant. Hence the results obtained wi th the improved system may not always be directly comparable with those obt ained using the original TEAC assay. Third, it is applicable to both aqueou s and lipophilic systems. (C) 1999 Elsevier Science Inc.