Synthesis and antioxidant activities of 2-oxo-quinoline-3-carbaldehyde Schiff-base derivatives

A series of 2-oxo-quinoline-3-carbaldehyde Schiff-base derivatives 4a(1)-4n(2) were designed and synthesized based on the 2-oxo-quinoline structure core as novel antioxidants. In vitro antioxidant activities of these compounds were evaluated and compared with commercial antioxidants ascorbic acid, BHT and BHA, employing DPPH() assay, ABTS(+) assay, O(2)(-) assay and OH() assay. The results showed that IC(50) of most compounds were lower than standard value 10mg/mL, indicating good antioxidant activities of these compounds. In addition, in vitro antioxidant activities screening revealed that 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of compounds 4b(2), 4e(1), 4e(2) and 4g(2), 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) cation (ABTS(+)) radical scavenging activities of compounds 4a(1), 4e(1), 4e(2), 4f(1), 4f(2), 4g(1), 4g(2), 4h(1), 4h(2), 4k(1), 4k(2), 4n(1) and 4n(2), superoxide anion radical scavenging activities of 4b(1), 4e(1), 4f(2), 4j(1), 4k(1), 4k(2), 4m(1), 4m(2), and 4n(2), and hydroxyl radical scavenging activity of almost all the compounds except 4f(1), 4f(2), 4j(2), 4l(1) and 4l(2) were better than that of the commercial antioxidant butylated hydroxytoluene (BHT).