Benzoic and cinnamic acid derivatives as antioxidants: structure-activity relation.
The antioxidant activity of four derivatives of benzoic acid was systematically compared with the activity of the four homologous derivatives of cinnamic acid. The couples of compounds differed for the kind of aromatic substitution (p-hydroxy, p-hydroxymethoxy, p-hydroxydimethoxy, dihydroxy). The antioxidant activity was measured using (i) a competition kinetic test, to measure the relative capacity to quench peroxyl radical and (ii) the in vitro oxidative modification of human low-density lipoprotein (LDL), initiated by 2,2'-azobis(amidinopropane) dihydrochloride or catalyzed by Cu(II). In both models, cinnamic acids were more efficient than their benzoic counterparts. As for the influence of the aromatic substitution, in the kinetic test the antioxidant activity increased in the sequence p-hydroxy < p-hydroxymethoxy < dihydroxy < p-hydroxydimethoxy. In contrast, in the LDL system, the dihydroxy acids had an antioxidant capacity equal to or higher than that of the p-hydroxydimethoxy acids.
Natella
F
F
Free Radical Research Group, National Institute of Nutrition, Roma, Italy.
Nardini
M
M
Di Felice
M
M
Scaccini
C
C
D000975:Antioxidants; D001565:Benzoates / Q000737:chemistry / Q000494:pharmacology*; D002934:Cinnamates / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000097:blood / Q000187:drug effects* / Q000378:metabolism; D013329:Structure-Activity Relationship
D000975:Antioxidants; D001565:Benzoates; D002934:Cinnamates; D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein