The second test is based on the ability of antioxidant molecules
to quench the ABTS+ (2,20-azinobis(3-ethylbenzothiazoline-6-sulphonic
acid) radical cation), a blue–green chromophore with characteristic
absorption at 734 nm; the addition of antioxidants to the
preformed radical cation reduces it to ABTS, determining a decolorization
(Pellegrini, Re, Yang, & Rice-Evans, 1999).