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

A series of 2-oxo-quinoline-3-carbaldehyde Schiff-base derivatives 4a1-4n2 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, O2− assay and OH assay. The results showed that IC50 of most compounds were lower than standard value 10 mg/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 4b2, 4e1, 4e2 and 4g2, 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) cation (ABTS+) radical scavenging activities of compounds 4a1, 4e1, 4e2, 4f1, 4f2, 4g1, 4g2, 4h1, 4h2, 4k1, 4k2, 4n1 and 4n2, superoxide anion radical scavenging activities of 4b1, 4e1, 4f2, 4j1, 4k1, 4k2, 4m1, 4m2, and 4n2, and hydroxyl radical scavenging activity of almost all the compounds except 4f1, 4f2, 4j2, 4l1 and 4l2 were better than that of the commercial antioxidant butylated hydroxytoluene (BHT).