Preparation and antitumor activity of some Schiff Bases of 2'-amino-4',5'-dichlorobenzenesulfonanilide and 2'-amino-p-toluenesulfonanilide

Synthesis, characterization, biological screening and determination of stability constants of N,N′-Bis[1-(4-chlorophenyl)ethylidene]ethane-1,2-diamine

A Schiff base ligand, N,N′-bis[1-(4-chlorophenyl)ethylidene]ethane-1,2-diamine (SBL), was synthesized by condensation of 4-chloroacetophenone with ethylenediamine in methanol in the presence of H2SO4 as catalyst. The structure of SBL was elucidated by spectroscopic (1H-NMR, 13C-NMR, IR and MS) and elemental analyses, and also confirmed by XRD. The SBL was used to prepare metal complexes 1-2 with Pb+2 and Cd+2, respectively. The structures of the complexes were elucidated by IR, MS and elemental analyses. On the basis of electronic spectra and magnetic moment data, octahedral geometry was proposed for the synthesized complexes 1-2. The conductivity data showed the non-electrolytic nature of the complexes 1-2. The SBL and complexes 1-2 were subjected to measure their biological potential against Staphylococcus aureus, Bacillus subtilis and Escherichia coli bacteria. SBL showed non-significant anti-bacterial potential whereas complexes showed moderate potential as compared to standard impinium. In the toxicity with brine shrimp larvae, complexes showed more toxic effect than the SBL. In the experiments to determine the stability constants of SBL with CuCl2, Cu(OAc)2, CoCl2 and Co(NO3)2; SBL showed highest stability constants with Cu(OAc)2 which is 1.550 × 107 at 1:1 (L:M) and second highest with Co(NO3)2 which is 6.861 × 106 at 3:2 (L:M).

Studies on free radical scavenging, cancer cell antiproliferation, and calf thymus DNA interaction of Schiff bases

Thirty-nine Schiff bases were synthesized by performing microwave-assisted condensation of the corresponding aldehydes and aromatic amines. Their reactive nitrogen species (RNS) scavenging activity and inhibitory effects against cancer cell growth were then subsequently investigated. Additionally, the interaction between the calf thymus DNA (ctDNA) and selected Schiff bases was evaluated using fluorescence spectroscopy, and their binding parameters were determined. The yields of the various compounds ranged from moderate to excellent (43-99%) after only a 2-min reaction. The hydroxylated Schiff bases 2, 8, 15, 16, 18, 20, 29, 32, 34, and 37 were found to be potent scavengers of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals with half-maximal scavenging concentration (SC₅₀) values lower than that of the positive control, resveratrol. The presence of hydroxyl substituents on the aromatic rings also proved essential to the cytotoxicity of the compounds. The binding constants (K_b) obtained using fluorescence spectroscopy ranged from 0.37 to 3.07×10⁵Lmol^-1, and were strongly influenced by the structure and hydroxylation degree. Schiff bases 3 and 8 showed promising cytotoxic activity, with half-maximal growth inhibitory (GI₅₀) values in the same order of magnitude as those exhibited by the reference drug, doxorubicin against various cell lines. Interestingly, these compounds also showed the highest K_b, suggesting that the cytotoxic activity could be related to their interaction with the DNA of the tumor cells. The results of this study highlighted some Schiff bases as potential lead compounds for the design of new free radical scavengers and anticancer agents.