Antioxidant and Cytotoxic Activity Studies in Series of Higher Amino Acid Schiff Bases

In this work, the antioxidant activity of the higher amino acid Schiff bases, which were prepared as the monosodium salts (1a-3a) and the neutral forms (1b-3b) was determined by DPPH scavenging assay. In pure MeOH solution, the scavenging ability of Schiff bases 1a-3a were higher than 1b-3b, but lower than ascorbic acid. The activity followed the order 3 (a,b) > 2 (a,b) > 1 (a,b). On the other hand, Schiff bases 2a and 3a behaved as the most effective scavengers of the DPPH radical in methanol-water mixture (v:v, 1:3). And, they were found to be have lower SC50 values in this mixture compared to pure methanol. In vitro cytotoxicity of these Schiff bases was studied against human cervical cancer cells (HeLa), human breast adenocarcinoma cells (MCF-7), and human normal embryonic kidney cells (HEK293). For HeLa cell line, Schiff bases 1a-3a exhibited a litttle high activity than 1b, but very low activity than doxorubicin. Schiff bases 2b and 3b had no cytotoxicity against HeLa cell. For MCF-7 cell line, Schiff bases 1a, 3a, 1b and 3b nearly were inactive at 100 mu M, whereas 2a increased cell proliferation in the all tested concentration range. Differently, Schiff base 2b showed the highest cytotoxicity and killed 90 percent of MCF-7 cells at concentration of 100 mu M. For HEK-293, doxorubicin was strongly cytotoxic. Despite this, Schiff bases 1a, 3a and 3b were inactive, whereas the others showed little weak toxicity.