nan Rahisuddin

Synthesis, characterization and antimicrobial activity of a new macrocycle and its transition metal complexes

The semicarbazone (L1) has been prepared by reaction of semicarbazide and glutaraldehyde (2 : 1) in distilled water and methanol (1 : 1). The reaction of semicarbazide, glutaraldehyde and diethyl oxalate in distilled water and methanol gave Schiff-base L2, 1,2,4,7,9,10-hexaazacyclo-pentadeca-10,15-dien-3,5,6,8-tetraone. Complexes of first row transition metal ions Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) have also been synthesized. The ligand and its complexes were characterized by elemental analysis, molar conductance, magnetic moment measurements, IR, 1H NMR, UV–Visible spectra and thermogravimetric analysis (TGA). Molar conductance values show that the complexes of Ni(II), Cu(II), Zn(II), Mn(II) and Co(II) are 1 : 2 electrolytes. On the basis of electronic spectral studies and molar conductance measurements an octahedral structure has been proposed for Mn(II) and Co(II) complexes, tetrahedral for Zn(II) complex and square planar for Ni(II) and Cu(II). The thermal behavior of the compounds, studied by TGA in a nitrogen atmosphere up to 800°C, reveal that the complexes have higher thermal stability than the macrocycle. All the synthesized compounds and standard drugs kanamycin (antibacterial) and miconazole (antifungal) have been screened against bacterial strains Staphylococcus areus, Escherichia coli and fungal strains Candida albicans, Aspergillus niger. The metal complexes inhibit growth of bacteria to a greater extent than the ligand.

Multi-spectroscopic and molecular docking studies on the interaction of new phthalimides with calf-thymus DNA: In vitro free radical scavenging activities

ABSTRACT In this study, we report the synthesis and biological evaluation of novel phthalimide based Schiff base derivatives as promising antioxidant and DNA-binding agents. The structural investigation of the synthesized compounds was determined by spectral and elemental analysis. In vitro DNA-binding studies of title compounds were carried out by UV–Vis, fluorescence, circular dichroism spectroscopic techniques, cyclic voltammetry, thermal denaturation studies, and hydrodynamic measurements to investigate their potential as DNA-binding agents. The DNA binding constant (Kb) of target compounds was obtained from absorption studies between 1.2 × 105 M−1 and 1.27 × 105 M−1, respectively, suggesting that the test compounds have shown good affinity toward calf-thymus DNA. The experimental results of DNA-binding studies reveal a non-intercalative mode of binding between DNA and the synthesized compounds, most probably groove binding. In addition, molecular docking techniques were performed to rationalize the observed binding affinities with the target DNA. Furthermore, antioxidant and free radical scavenging activities of the synthesized compounds were carried out to find out their pharmacological potential. The results indicate that the title compounds displayed good antioxidant activity against DPPH (IC50: 0.727 and 0.656 mg/mL) and H2O2 radicals (IC50: 1.072 and 0.911 mg/mL) comparable to standard ascorbic acid.

Isolation of proton transfer complexes containing 4-picolinium as cation and pyridine-2,6-dicarboxylate complex as anion: crystallographic and spectral investigations, antioxidant activities and molecular docking studies

Three novel complexes with stoichiometry [4-pic-H][M(pda)2]·2H2O [M = Cr (1), Fe (2) and Co (3); H2pda = pyridine-2,6-dicarboxylic acid and 4-pic = 4-picoline] have been prepared. The complexes (1–3) are characterized using elemental analysis, TGA, CV, FTIR, ESI mass, 1H & 13C NMR, EPR, UV Visible, fluorescence, magnetic and X-ray studies. Spectral data ascertained the bonding modes and the geometry of the complexes. Single crystal X-ray data of (2) and (3) revealed the formation of proton transfer complexes in which a proton is transferred from the H2pda moiety to the pyridine nitrogen of 4-pic. Thermal and ESI mass data confirmed the proposed stoichiometry of the complexes. Cyclic voltammetric (CV) studies confirm the formation of MII/MIII quasi-reversible redox couples in solution. The antioxidant activity of (3) assessed using DPPH and hydrogen peroxide assays has suggested that the present compounds may be used as potent antioxidants. Molecular docking studies performed for (2) and (3) reveal that the present complexes can efficiently bind with DNA receptor with free energy of binding (FEB) values of −314 (2) and −276.8 kcal mol−1 (3). The molecular docking studies indicated a higher binding ability of (2) to DNA compared to that of (3).

Extracellular synthesis of silver dimer nanoparticles using Callistemon viminalis (bottlebrush) extract and evaluation of their antibacterial activity

ABSTRACT Green methods are powerful tools to minimize the use of toxic chemicals which are harmful to human beings as well as environment. The present study focuses on the use of aqueous extract of Callistemon viminalis (bottlebrush) leaves for the synthesis of silver nanoparticles. The extract was used as a bioreductant and the polyphenols and flavanoids present in extract are responsible for the reduction of Ag+ ions to zero valent silver nanoparticles. The effect of concentration of Ag+ ions and cetyltrimethylammonium bromide on the nanoparticles was examined. On increasing the concentration of stabilizer, different morphological nano-couples are formed. The successful formation of silver nanoparticles was demonstrated by using ultraviolet–visible, transmission electron microscope and scanning electron microscope. Transmission electron microscope image analysis showed wide size distribution having dimer nanoparticles of hexagonal-triangular, square-triangular, spherical-triangular, spherical-spherical square-spherical morphologies. The antibacterial activity of extract reduced silver nanoparticles against four strains viz. Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Salmonella typhimurium was evaluated by calculation of minimum inhibitory concentration and minimum bactericidal concentration. The results show that synthesized nanoparticles could inhibit the growth of various bacteria tested.

Experimental and molecular docking investigation on DNA interaction of N-substituted phthalimides: antibacterial, antioxidant and hemolytic activities.

A series of Schiff base molecules derived from a phthalimide scaffold was investigated as efficient antibacterial, antioxidant and DNA-interacting agents. The spectroscopic characterization of these derivatives was studied in detail using elemental analysis and spectroscopic techniques. The DNA-binding profile of title molecules against Ct-DNA (calf thymus) was investigated by absorbance, fluorescence, hydrodynamics and thermal denaturation investigations. The bacterial inhibition potential of these molecules was investigated against Escherichia coli and Staphylococcus aureus. Molecule 3c emerged as the most active against S. aureus (IC50 : 14.8 μg/mL), whereas compounds 3a and 3b displayed potential antibacterial activities against E. coli (IC50 : 49.7 and 67.6 μg/mL). Molecular docking studies of these compounds against GlcN-6-P synthase were carried out to rationalize antibacterial efficiency of these molecules. These newly synthesized molecules were screened for their scavenging capacity against 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and H2 O2 free radicals and the results were compared with ascorbic acid as synthetic antioxidant. The title molecules 3a, 3b and 3e showed less than 20% hemolysis, which indicated their significant non-toxic behavior.

Synthesis and Characterization of New Macrocycles Containing Pendant Groups

Abstract The new ligands, 1,5,8,12‐tetraaza‐4‐(1′,1′‐dimethylethyl)‐2‐(1″,1″,2″,2″,3″,3″,3″‐heptafluoropropyl)‐9,11‐(dimethyl)‐cyclotetradeca‐1,4,8,11‐tetraene (L1) and 1,5,9,13‐tetraaza‐4‐(1′,1′‐dimethylethyl)‐2‐(1″,1″,2″,2″,3″,3″,3″‐heptafluoropropyl)‐10,12‐(dimethyl)‐cyclohexadeca‐1,4,9,12‐tetraene (L2), have been prepared by the reaction of 1,1,2,2,3,3,3‐heptafluoro‐7,7‐dimethyl‐4,6‐octanedione with ethylenediamine and acetyl acetone (L1) and 1,1,2,2,3,3,3‐heptafluoro‐7,7‐dimethyl‐4,6‐octanedione with 1,3‐diaminopropane and acetylacetone (L2), respectively. Their complexes with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) ions have also been synthesized and characterized by elemental analyses, magnetic susceptibility measurements, molar conductance measurements, IR, EPR, 1H NMR, and UV‐Visible spectra. The molar conductance values show that the complexes of Fe(III) and Cr(III) are 1:1 electrolytes, the Ni(II) and Cu(II) complexes are 1:2 electrolytes while those of Mn(II), Co(II), and Zn(II) appear to be non‐ionic. An octahedral structure has been proposed for all of these metal ions except for those of Cu(II) and Ni(II), which appear to be square‐planar. The β values indicate a considerable orbital overlap in the metal–ligand bond. All of the compounds have been tested against gram‐positive bacteria of Staphylococcus aureus and gram‐negative bacteria of Escherichia coli. The results show that these compounds inhibit the growth of bacteria.

Nanoparticles as Targeted Drug Delivery Agents: Synthesis, Mechanism and Applications

Extensive research is going on therapeutic delivery but the problem to develop a proper carrier still exists that can deliver drugs to specific sites of the body or target cells to treat diseases. The problems of therapeutic delivery are associated with low efficacy caused by carrier plasma instability and high toxicity, clearance by the reticulo endothelial system (RES), as well as the existence of various intracellular barriers. Today nanotechnology is a developing field and applications of nanoparticles in drug delivery succeed to overcome the above hurdles. Nanoparticles enhance the gathering of drug in the affected tissues based on the surface properties and enhanced permeability and retention (EPR) effect. Therefore, nanoparticles increase the uptake of the drugs by cells and minimize the adverse effect through both specific and enhanced interactions between the targeted cells and nanoparticles. The small size of nanoparticles is responsible for its high surface area which is responsible to readily interact with biomolecules at the surface as well as inside the cells. This helps the target specificity for therapeutics. The use of nanoparticles helps to reduce the toxicity of the therapeutic agent, the treatment efficacy is improved, and side effects are decreased. The nanoparticles can be used in a stealth mode in which therapeutic agents are loaded into nanoparticles which are not identified by the immune system and nanoparticles carry the drugs to selectively targets. Recent research in the field of drug delivery is mainly focused on use of nanoparticles as drug carriers for health challenging diseases such as cancer, HIV, and diabetes. The common treatment for these diseases is not so much effective and most of the time the cure is death. Nanoparticles have been identified to securely carry the drugs to infected cells that can be a useful tool to fight the diseases. In case of cancer, traditional chemotherapy might not be successful because anticancer drugs disperse to the whole body and destroy both the normal and affected cells. Nanoparticles can replace this treatment with a more promising one that could meet these challenges. Current chapter is mainly focused on the targeted drug delivery by using nanoparticles. The mechanism of action of targeted delivery is discussed in detail with the applications of different types of nanoparticles in targeted delivery. The chapter also put some light on the synthetic procedures of nanoparticles for use in targeted drug delivery. The present chapter will be of great importance to both students and researchers.

New phthalimide-appended Schiff bases: Studies of DNA binding, molecular docking and antioxidant activities.

Herein, we investigated new phthalimide-based Schiff base molecules as promising DNA-binding and free radical scavenging agents. Physicochemical properties of these molecules were demonstrated on the basis of elemental analysis, ultraviolet-visible (UV-Vis), infra-red (IR), 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy. All spectral data are agreed well with the proposed Schiff base framework. The DNA-binding potential of synthesized compounds were investigated by means of UV-visible, fluorescence, iodide quenching, circular dichroism, viscosity and thermal denaturation studies. The intrinsic binding constants (Kb ) were calculated from absorption studies were found to be 1.1xa0×xa0104 and 1.0xa0×xa0104 xa0M-1 for compounds 2a and 2b suggesting that compound 2a binding abilities with DNA were stronger than the compound 2b. Our studies showed that the presented compounds interact with DNA through groove binding. Molecular docking studies were carried out to predict the binding between Ct-DNA and test compounds. Interestingly, in silico predictions were corroborated with in vitro DNA-binding conclusions. Furthermore, the title compounds displayed remarkable antioxidant activity compared with reference standard.

Synthesis, crystal structures and spectral characterization of Cu(II) and Mn(II) complexes of 4-hydroxy-3-methoxybenzaldehyde: antioxidant properties and molecular docking studies

Abstract [Cu(L)2(H2O)2] (1) and [Mn(L)2(H2O)2] (2) (HL = 4-hydroxy-3-methoxybenzaldehyde) were synthesized and characterized using elemental, spectral (FTIR, ESI-MS, UV–visible, fluorescence and EPR), thermal, cyclic voltammetric, powder, and single crystal X-ray crystallographic studies. Spectral and X-ray data ascertained the structural features, binding modes of ligand and distorted octahedral geometry around the metal ions. Cyclic voltammetric studies confirmed the formation of a quasi reversible redox couple in solution. Crystal structure analysis of 1 and 2 reveal the presence of non-covalent interactions, resulting in a 1-D polymeric chain. Antioxidant properties (using DPPH and hydrogen peroxide assay) and molecular docking studies (using 1BNA) are also examined. The binding free energies (calculated from docked models), −270 (1) and −295 kJ mol−1 (2), suggest that the complexes reasonably bind to DNA, and the DNA-binding affinity of 2 is stronger than that of 1.