The structure-antioxidant activity relationship of dehydrodiferulates. (15th December 2018) - Jia, Yuan
Graphical abstract: Highlights: All possible diferulic acids and their esters evaluated for antioxidant activity. Methods assaying antioxidant provided consistent results except for 8-8-lactone DC. Antioxidant capacity of ferulate dimers varied with the linkage types. Conjugated structure para to phenolic hydroxyl led to better antioxidant activity. Phenol group was responsible for the antioxidant activity but not a deciding factor. Abstract: In this study, 11 dehydrodiferulic acids (DFAs) and 8 diethyl dehydrodiferulates (DEFs) were synthesized and evaluated by Trolox equivalent antioxidant capacity (TEAC) and 2, 2′-diphenyl-1-picrylhydrazyl (DPPH) assays for their antioxidant properties to understand the Structure-Antioxidant Activity Relationship (SAR) of these dehydrodiferulates. In both assays, the order of antioxidant activity for all tested ferulic acid dimers were consistent except for 3-(4-Hydroxy-3-methoxy-benzylidene)-5-(4-hydroxy-3-methoxy-phenyl)-3H-furan-2-one (2, 8-8-lactone DC DFA, not occurred naturally) being the best antioxidant by TEAC test. The order of antioxidant activity of diferulic acid ethyl esters, evaluated by both assays, was not consistent; however, TEAC and DPPH assays provided consistent results for certain set of ethyl diferulates. In this study most of dimeric ferulates, with three exceptions, showed higher radical-scavenging efficacy than the monomers. Comparing the antioxidant activities of the tested diferulates suggested that the phenolic hydroxyl group, electron donating methoxyl group, and stable conjugated transient structures dictate the antioxidant activity of diferulates.