Biological evaluation of nano-sized novel Schiff base ligand-based transition metal complexes

This study reports on the preparation, characterization, and biological evaluation of nano-sized novel Schiff base ligand (SBL) based transition metal complexes, which were synthesized by reacting metal chloride salts with SBL. The SBL and its complexes were characterized using different analytical and spectroscopic techniques including 1H - 13C NMR, UV–Vis, IR, CHN elemental analysis, TGA, DTA, SEM, TEM, XRD, ICP-MS, molar conductivity, and magnetic susceptibility. The characterization results showed that the complexes had formula [MLCl2 (H2O)2], where M = V3+ and Cr3+ or [M(L)2(H2O)2], where M = Mn2+, Ni2+, Zn2+ and Cd2+. The ligand behaved as a monobasic bidentate chelator bonding the metal via the deprotonated hydroxyl oxygen and azomethine nitrogen, adopting a distorted octahedral structure. XRD spectroscopy and SEM confirmed the complexes to be crystalline, with particle sizes ranging from 50 to 100 nm. The prepared nano-compounds were evaluated for their in vitro antimicrobial, antifungal, and anticancer activities, as well as in vivo oral toxicity tests. In-vitro antimicrobial activities demonstrated that the Zn2+ complex was the most active against bacteria, while the Cr3+ complex was the most active against fungi. The V3+ complex was shown to be the least active against all microorganisms tested. Moreover, the Zn2+ complexes showed the most effective anticancer activity against WI38 and MCF-7 cell lines with IC50 values of 39.82 and 7.31 µM, respectively, while, the Cr3+ complex was the most effective against the HEPG-2 cell line with an IC50 of 11.83 µM. In addition, in vivo, oral toxicity of (SBL) ligand and its metal complexes showed a safety limit of up to 2000 mg/kg of rat’s dose in the level of liver and kidney histology and hematology and biochemical analysis. We concluded that these novel nano-synthesized complexes can used in therapeutics to avoid microbial resistance problems.