Antioxidant, tautomerism and antibacterial studies of Fe(III)-1,2,4-triazole based complexes

Antimicrobial Agents Based on Metal Complexes: Present Situation and Future Prospects

The rise in antimicrobial resistance is a cause of serious concern since the ages. Therefore, a dire need to explore new antimicrobial entities that can combat against the increasing threat of antibiotic resistance is realized. Studies have shown that the activity of the strongest antibiotics has reduced drastically against many microbes such as microfungi and bacteria (Gram-positive and Gram-negative). A ray of hope, however, was witnessed in early 1940s with the development of new drug discovery and use of metal complexes as antibiotics. Many new metal-based drugs were developed from the metal complexes which are potentially active against a number of ailments such as cancer, malaria, and neurodegenerative diseases. Therefore, this review is an attempt to describe the present scenario and future development of metal complexes as antibiotics against wide array of microbes.

Metal incorporated aminothiazole-derived compounds: synthesis, density function theory analysis, in vitro antibacterial and antioxidant evaluation

The present study advocates the combined experimental and computational study of metal-based aminothiazole-derived Schiff base ligands. The structure and electronic properties of ligands have been experimentally studied by spectroscopic methods (UV-Vis, FT-IR, ¹H-NMR and ¹³C-NMR), mass spectrometry, elemental analysis and theoretically by density function theory (DFT). Computational calculations employing the B3LYP/6-31 + G(d,p) functional of DFT were executed to explore the optimized geometrical structures of ligands along with geometric parameters, molecular electrostatic potential (MEP) surfaces and frontier molecular orbital (FMO) energies. Global reactivity parameters estimated from FMO energy gaps signified the bioactive nature of ligands. The synthesized ligands were used for chelation with 3d-transition metals [VO(IV), Cr(III), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)] in 1 : 2 (metal : ligand) molar ratio. The spectral and magnetic results confirmed the formation of octahedral geometry around all the divalent and trivalent metal centres, whereas the tetravalent vanadyl centres were confirmed to have square-pyramidal geometry. All the as-synthesized compounds were investigated for in vitro antibacterial potential against two Gram-negative (Salmonella typhimurium and Escherichia coli) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacteria. Antibacterial assay results displayed pronounced activity, and their activity is comparable to that of a standard drug (streptomycin). The antioxidant potential of these compounds was assessed by employing diphenyl picryl hydrazide radical scavenging activity. The results displayed that all the metal chelates have exhibited more bioactivity in contrast with free ligands. The chelation was the main reason for their enhanced bioactivity. These results indicated that the thiazole metal-based compounds could be exploited as antioxidant and antimicrobial candidates.

A review: Pharmacological aspects of metal based 1,2,4-triazole derived Schiff bases

Clinical reports have highlighted the radical increase of antibiotic resistance. As a result, multidrug resistance has emerged as a serious threat to human health. Many organic compounds commonly used as drugs in the past, no longer have pure organic mode of action rather need bio-transformation or more activation. Bulk of research has shown that they need trace amount of metal ions incorporated within the chemistry of bioactive molecules for enhancement of their potentiality to fight aggressively against resistance. The deficiency of some metal ions can also be responsible for many diseases like growth retardation, pernicious anemia and heart diseases in infants. To overcome these problems, there is a need to introduce novel strategies which have new mechanism of action along with significant spectrum of biological activity, enhanced safety and efficacy. Bioinorganic compounds have played imperative role in developing the new strategy in the form of "Metal Based Drugs". In current years there have been momentous rise of interest in the application of metal based Schiff base compounds to treat various diseases which are difficult to be treated with conventional methodologies. The unique properties of metal chelates acting as an intermediate between conventional organic and inorganic compounds provided innovative opportunities in the field of pharmaceutical chemistry. In this review, we have exclusively focused on the search of metal based 1,2,4-triazole derived Schiff base compounds (synthesized, reported and reviewed in the past ten years) that possess various biological activities such as antifungal, antibacterial, antioxidant, antidiabetic, anthelmintic, anticancer, antiproliferative, cytotoxic and DNA-intercalation activity.

New Antimicrobial Strategies Based on Metal Complexes

Traditional organic antimicrobials mainly act on specific biochemical processes such as replication, transcription and translation. However, the emergence and wide spread of microbial resistance is a growing threat for human beings. Therefore, it is highly necessary to design strategies for the development of new drugs in order to target multiple cellular processes that should improve their efficiency against several microorganisms, including bacteria, viruses or fungi. The present review is focused on recent advances and findings of new antimicrobial strategies based on metal complexes. Recent studies indicate that some metal ions cause different types of damages to microbial cells as a result of membrane degradation, protein dysfunction and oxidative stress. These unique modes of action, combined with the wide range of three-dimensional geometries that metal complexes can adopt, make them suitable for the development of new antimicrobial drugs.

Novel indole-based melatonin analogues substituted with triazole, thiadiazole and carbothioamides: studies on their antioxidant, chemopreventive and cytotoxic activities

Melatonin (MLT) is a well-known free-radical scavenger, involving in the prevention of cellular damage that can lead to cancer, ageing and a variety of neurodegenerative diseases. Research on MLT-related compounds has been required to optimise the maximum pharmaceutical activity with the lowest side effects. In our ongoing research, we have synthesized new indole-based MLT analogues as potential antioxidant agents by modifying the MLT molecule. In this study, we build on previous findings, through the synthesis, characterization and in vitro antioxidant profiling of a series of new indole-based MLT analogues which possess triazole, thiadiazole and carbothioamides on the third position on the indole ring. In vitro antioxidant activity was investigated by evaluating their reducing effect against oxidation of a redox sensitive fluorescent probe and their radical scavenging activity was assessed via the DPPH assay. In addition, in vitro cytotoxic effects of newly synthesized compounds were investigated in CHO-K1 cells using the MTT assay.

Ni(II), Pd(II) and Pt(II) complexes of (1H-1,2,4-triazole-3-ylimino)methyl]naphthalene-2-ol. Structural, spectroscopic, biological, cytotoxicity, antioxidant and DNA binding

Metal complexes of the general formula [ML(H2O)Cl]nH2O; n=1 for M=Ni and Pt and n=2 for M=Pd, L=Schiff base (HL) derived from the condensation of 3-amino-1,2,4-triazole and 2-hydroxy-1-naphthaldehyde, were prepared. The synthesized ligand and its metal complexes were characterized on the basis of elemental analyses, spectral and magnetic studies as well as thermal analysis. The IR spectra revealed that the ligand is coordinated to the metal ions in bidentate manner via the N-atom of the azomethine group and the phenolic OH group. Square planar geometry was proposed for Pd(II) and Pt(II) complexes and tetrahedral for Ni(II) complex. The ligand and its metal complexes were screened against the sensitive organisms Escherichia coli as Gram-negative bacteria, Staphylococcus aureus as Gram-positive bacteria, Aspergillus flavus and Candida albicans as fungi. Moreover, the anticancer activity of the ligand and its metal complexes was evaluated in liver carcinoma (HEPG2) cell line. The results obtained indicated that the Schiff base ligand is more effective than its metal complexes towards the tested cell line. Ni(II), Pd(II) and Pt(II) complexes as well as the free Schiff base ligand were tested for their antioxidant activities. The DNA-binding properties of the studied complexes have been investigated by electronic absorption and viscosity measurements.