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Macrocyclic ligands (MacL 1 -MacL 3 ) and Co(II) complexes were synthesized via template condensation of o-phenylenediamine with various aromatic dicarboxylic acids. The elemental analysis, FT-IR, mass spectrometry, 1 H NMR, 13 C NMR, UV-vis, SEM analysis, powder X-ray diffraction, thermogravimetric (TG) analysis, electrochemical studies, and DFT analysis were used to characterize these synthesized ligands and their cobalt (II) complexes. TGA analysis to determine the stability and decomposition kinetic parameters. In element analysis, the percentage of different elements present and also the stoichiometry of compounds were confirmed. The proposed framework for tetraaza macrocyclic cobalt (II) complexes was supported by spectral analysis, which also revealed distorted octahedral geometry surrounding the central metal atom. The molecular structure of cobalt (II) complexes was also optimized theoretically, and their electronic or thermodynamic parameters were obtained from density functional theory (DFT). The synthesized ligands and their cobalt (II) complexes were tested against bacteria: Escherichia coli, Bacillus subtitles. Candida albicans were tested for antifungal properties. It was found that ligands and complexes show good antimicrobial results. Finally, using the Auto Dock VinaPyRx programme, molecular docking studies were used to evaluate the biological significance of the synthesized ligands to identify the probable and efficient binding mechanisms between the various ligands and the active site of the receptor protein. Graphical abstract Antimicrobial, DFT, and Docking representation of Cobalt (II) macrocyclic complexes Supplementary Information The online version contains supplementary material available at 10.1007/s12039-022-02109-2.

Pongamia pinnata (L.) Pierre (Fabaceae), popularly known as "Karanj" or "Karanja" in Hindi, and Indian beech in English, is a medium-sized glabrous tree. In the present study we report the antihyperglycemic activity of stem bark of alcohol extract of Pongamia pinnata (PPSBAE). Based on acute oral toxicity data, PPSBAE showed no mortality in normal mice up to 5,000 mg/kg. PPSBAE was administered as three doses (i.e., 100, 200, and 400 mg/kg) to diabetic mice, and the serum glucose level and body weight were measured. The onset of serum glucose reduction was observed at 2 h (130.32 mg/dl), peak at 4 h (151.79 mg/dl) and sustained at 6 h, but waned at 24 h. In the subacute study, maximum reduction (305.72 mg/dl) in serum glucose was observed at a dose of 400 mg/kg on day 28. An oral glucose tolerance test (OGTT) was carried out after administration PPSBAE (200 mg/kg) in non-diabetic mice previously loaded with 2.5 g/kg, per oral (p.o.) of glucose. The PPS-BAE (200 mg/kg) showed increased glucose threshold in non-diabetic mice. These results suggest that the PPSBAE possesses antihyperglycemic activity.

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The threat of antibiotic resistance to public health is becoming a major cause of mortality on a worldwide scale. It has stimulated the interest of researchers in the development of novel antibiotics. Therefore, a new series of Schiff base macrocyclic ligands (N8MacL1‐N8MacL3) and their bivalent manganese complexes were synthesized and analyzed for biological activities. Characterization of the synthesized macrocyclic compounds was done by various spectroscopic techniques like elemental analysis, infrared (IR), proton nuclear magnetic resonance (NMR), 13C NMR, ultraviolet–visible, mass, electron paramagnetic resonance (EPR), and powder X‐ray diffraction (PXRD). Based on spectral studies, an octahedral environment has been proposed around the manganese metal center in the synthesized macrocyclic complexes. Density functional theory (DFT) calculations were used to evaluate the stability and the electronic properties of the synthesized macrocyclic ligands and their Mn (II) complexes. The structures of the synthesized compounds were optimized by using the def2‐SVP basis set at B3LYP level. The synthesized compounds were evaluated against gram‐positive bacterial strains (Staphylococcus aureus and Bacillus cereus), gram‐negative bacterial strains (Escherichia coli and Xanthomonas campestris), and fungal strains (Candida albicans and Fusarium oxysporum) for their antimicrobial activity by agar well diffusion method. Among all of the newly synthesized compounds, the macrocyclic complex [Mn(N8MacL3)Cl2] exhibited high antimicrobial activity against all bacterial and fungal strains except S. aureus. The virtual screening of synthesized Schiff base ligand [L], macrocyclic ligands (N8MacL1‐N8MacL3), and their Mn (II) complex [Mn(N8MacL1)Cl2‐Mn(N8MacL3)Cl2] are performed against the receptors, which were used for in vitro antimicrobial testing, to identify the most plausible drug–ligand interactions. The scavenging activity of DPPH radicals was utilized to study the antioxidant activity of the synthesized compounds. The macrocyclic metal complex [Mn(N8MacL3)Cl2] exhibited excellent antioxidant activity.

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Many distinct amino acid and aromatic amine-derived transition metal complexes are used as physiologically active compounds. A few Cobalt (II) complexes have been synthesized by reacting cobalt (II) chloride with 1, 8-diaminonapthalene-based tetraamide macrocyclic ligands in an ethanolic media. These synthesized ligands (TAML 1-3 ) and associated Co(II) complexes were fully characterized with various spectroscopic techniques, such as IR, NMR, CHN analysis, EPR, molar conductance, and magnetic susceptibility measurements, TGA, UV–visible spectra, powder X-ray diffraction and DFT analysis. The IR spectra reveal interactions between the core metal atom and ligands through N of 1, 8-diaminonapthalene. The distorted octahedral geometry of synthesized Co(II) macrocyclic complexes were confirmed by ESR, UV–Vis and DFT studies. The synthesized ligands (TAML 1 -TAML 3 ) and their Co(II) complexes were tested for antimicrobial activity against A. niger, C. albicans, and F. oxysporum in addition to bacteria like S. aureus, B. subtilis, and Gram-negative bacteria like E. coli. The ligand TAML 1 and complex [Co(TAML 1 )Cl 2 ] showed an excellent antibacterial activity. The minimum inhibitory concentration of TAML 1 and [Co(TAML 1 )Cl 2 ] against S. aureus were found to be 7 mm and 10 mm zone of inhibition at 500 ppm, respectively, compared to drug ampicillin (3 mm). Additionally, each molecule exhibited notable antioxidant activity. The biological significance of the synthesized compounds was then evaluated by molecular docking experiments with the active site of the receptor protein such as Sars-Cov-2 , C. Albicans, X. campestris and E. coli . The molecular docking assisted data strongly correlated to the experimental approach of antimicrobial activity. Graphical Abstract Supplementary Information The online version contains supplementary material available at 10.1007/s11696-023-02843-y.

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