Cinnamates and hydroxybenzoates in the diet: antioxidant activity assessed using the ABTS•+ radical cation
Examines the antioxidant activities of a range of hydroxy-substituted phenolic acids by estimating their relative abilities to scavenge the ABTS_+ radical cation generated in the aqueous phase, expressed as the Trolox equivalent antioxidant capacity (TEAC value). These common food components have varying reducing abilities, dependent on the positions and extent of hydroxylation of their phenol ring. Reports the research results which suggest that some simple phenolic acids are most effective antioxidants, up to two to three times as active as vitamin C. Their relative abundance in fruits, oils, etc. indicates that they may be highly significant contributors to the overall dietary antioxidant intake. Para-coumaric acid (4-hydroxycinnamic acid) was found to have a TEAC value of 2.2mM (more than twice the antioxidant activity of vitamin C). Ferulic acid (3-methoxy, 4-hydroxycinnamic acid), the active component of oryzanol (rice bran oil) was found to have a TEAC value of 1.9 mM and gallic acid (3, 4, 5-trihydroxybenzoic acid) a TEAC of 3.0mM (i.e. three times the antioxidant activity of vitamin C). Discusses the significance of these and other related compounds as food antioxidants and as non-nutrient antioxidants in the diet.