Antimicrobial and antitumor activity of S-methyl dithiocarbazate Schiff base zinc(II) complexes

Abstract Schiff bases (SB) obtained from S-methyl dithiocarbazate and aromatic aldehydes: salicylaldehyde (H 2 L 1 ), o-vanillin (H 2 L 2 ), pyridoxal (H 2 L 3 ) and 2,6-diformyl-4-methylpHenol (H 3 L 4 ), and their corresponding Zn(II)-complexes (1–4), are synthesized. All compounds are characterized by elemental analyses, infrared, UV–Vis, nuclear magnetic resonance spectroscopy and mass spectrometry. The structures of H 2 L 2 and [Zn 2 (L 1 ) 2 (H 2 O)(DMF)] (1a) (DMF = dimethylformamide) are solved by single crystal X-ray diffraction. The SB coordinates the metal center through the O phenolate , N imine and S thiolate atoms. The radical scavenging activity is tested using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, with all ligand precursors showing IC 50 values ~40  μ M. Cytotoxicity studies with several tumor cell lines (PC-3, MCF-7 and Caco-2) as well as a non-tumoral cell line (NHDF) are reported. Interestingly, 1 has relevant and selective antiproliferative effect against Caco-2 cells (IC 50 = 9.1 μM). Their antimicrobial activity is evaluated in five bacterial strains ( Klebsiella pneumoniae , Acinetobacter baumannii, Listeria monocytogenes , Pseudomonas aeruginosa and Staphylococcus aureus ) and two yeast strains ( Candida albicans and Candida tropicalis ) with some compounds showing bacteriostatic and fungicidal activity. The minimal inhibitory concentration (MIC 90 ) of H n L (Gaynor and Griffith, 2012; Chen et al., 2017; Franklin and Costello, 2007; Franklin et al., 2009 [ [1] , [2] , [3] , [4] ] ) against Mycobacterium tuberculosis is also reported, with H 2 L 2 and H 3 L 4 showing very high activity (MIC 90 3 L 4 and [Zn 2 (L 4 )(CH 3 COO)] (4), both showing high binding constants to BSA (ca. 10 6 M −1 ) and ability to bind DNA. Overall, the reported compounds show relevant antitumor and antimicrobial properties, our data indicating they may be promising compounds in several fields of medicinal chemistry.