Many food ingredients like polyphenols have antioxidative activity such as a free radical scavenging ability etc., which is evaluated by measuring its potential in vitro.1,2) Antioxidant capacity assays can be classified into two types based on HAT (hydrogen atom transfer) reactions and ET (electron transfer) reactions. HAT-based assays include the ORAC (oxygen radical absorbance) method3,4) analyzing the fluorescent intensity of fluorescein decomposed by a peroxy radical sourced from AAPH (2,2'-azobis(2-methylpropionamidine) dihydrochloride), and the TRAP (total radical trapping antioxidant parameter) method5) analyzing the fluorescent intensity of luminol oxidized by a similar peroxy radical. ET-based assays include the DPPH method6) analyzing DPPH (1,1-diphenyl-2-picrylhydrazyl) colorimetrically, and the TEAC (trolox equivalence antioxidant capacity) method7) analyzing ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid ammonium salt)) colorimetrically, and so on.
Trolox is a water-soluble antioxidant, which was synthesized as a vitamin E derivative in 1974.8) Trolox has been used as a standard antioxidant for these antioxidant capacity assays.
