In vitro and in silico studies of antibacterial activities of secofriedelane derivatives from Senna alata (L) Roxb.

In this study, six compounds were obtained from a methanolic extract of air-dried leaves of Senna alata and one of them, a triterpenoid (secofriedelane) named as 7-(2-carboxyethyl)-3, 4b, 6a, 8, 10a, 12a-hexamethyl-8-vinyloctadecahydrochrysene-3-carboxylic acid (5) was isolated for the first time from this plant. Then, its chemical structure was detailed and characterised by FT-IR, 1H and 13C- NMR and ESI-MS. Besides, two chemical-modified derivatives of secofriedelane (5a, 5b) were synthesised by methylation and allylation reactions, respectively, and their in vitro antibacterial activities were also evaluated. The results revealed that all the triterpenes showed, against gram-positive and -negative bacterial strains, good and moderate antibacterial activities with bactericidal effects that were enhanced by the methyl groups and altered with the allyl ones. Moreover, the molecular docking results of 5, 5a and 5b in the DNA gyrase (2XCT) active site showed that triterpene 5 has a good score very close to reference (ciprofloxacin).

Experimental and theoretical analyses and investigation of intermolecular interactions and antibacterial activity of a novel proton transfer compound:8-hydroxyquinolinium oxalate monohydrate.

A novel proton transfer compound, 8-hydroxyquinolinium oxalate monohydrate was synthesised by solid state grinding of 8-hydroxyquinoline and oxalic acid. The resulting compound is characterised by single crystal X-ray diffraction (SXRD), FT-IR, UV-Visible, TG/DTG, DTA and DSC analyses. The compound crystallizes in monoclinic crystal system with space group P21/n. The carboxylate oxygen O2 which acts as a tetrafurcated acceptor of four hydrogen bonds is the main feature of the crystal structure. The molecules are linked together by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds. Carbonyl-carbonyl interactions play a crucial role in stabilising the crystal packing. Hirshfeld surface analysis and the associated finger print plots facilitates the comparison of intermolecular interactions. The nature of charge density distribution and topological parameters of the proton transfer region N1-H1A⋯O2 hydrogen bond reveals that the bond has considerable covalent character. Natural Bond Orbital (NBO) has been extended to analyse the nature and strength of intermolecular interactions. Topology analysis using ELF and LOL reveals electron localisation and depletion regions. ADMET analysis reveals that the compound satisfies Lipinski's rule of five and drug likeness. Antibacterial activity was screened against 3 g positive - Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus and 2 g negative strains- Klebsiella pneumonia and Salmonella typhi by employing disc diffusion method.

Preparation of NLCs-Based Topical Erythromycin Gel: In Vitro Characterization and Antibacterial Assessment.

In the present study, erythromycin (EM)-loaded nanostructured lipid carriers (NLCs) were prepared by the emulsification and ultra-sonication method. EM-NLCs were optimized by central composite design using the lipid (A), pluronic F127 (B) and sonication time (C) as independent variables. Their effects were evaluated on particle size (Y1) and entrapment efficiency (Y2). The optimized formulation (EM-NLCs-opt) showed a particle size of 169.6 ± 4.8 nm and entrapment efficiency of 81.7 ± 1.4%. EM-NLCs-opt further transformed into an in-situ gel system by using the carbopol 940 and chitosan blend as a gelling agent. The optimized EM-NLCs in situ gel (EM-NLCs-opt-IG4) showed quick gelation and were found to be stable for more than 24 h. EM-NLCs-opt-IG4 showed prolonged drug release compared to EM in situ gel. It also revealed significant high permeation (56.72%) and flux (1.51-fold) than EM in situ gel. The irritation and hydration study results depicted no damage to the goat cornea. HET-CAM results also confirmed its non-irritant potential (zero score). EM-NLCs-opt-IG4 was found to be isotonic and also showed significantly (p < 0.05) higher antimicrobial activity than EM in situ gel. The findings of the study concluded that NLCs laden in situ gel is an alternative delivery of erythromycin for the treatment of bacterial conjunctivitis.

Synthesis and characterisation of zinc oxide modified biorenewable polysaccharides based sustainable hydrogel nanocomposite for Hg2+ ion removal: Towards a circular bioeconomy.

Industrial metal ion pollution has been considered the chief source of water contaminants all over the world. In the present research, we have prepared gum tragacanth cross-linked 2-hydroxyethyl methacrylate-co-acrylamide (GT-cl-(HEMA-co-AAm)) hydrogel and gum tragacanth cross-linked 2-hydroxyethyl methacrylate-co-acrylamide/zinc oxide (GT-cl-(HEMA-co-AAm)/ZnO) hydrogel composite with better Hg2+ adsorption capability. GT-cl-(HEMA-co-AAm)/ZnO hydrogel composite (154.8 mg g-1) exhibited higher Hg2+ adsorption than GT-cl-(HEMA-co-AAm) hydrogel. To address the performance of GT-cl-(HEMA-co-AAm) hydrogel and GT-cl-(HEMA-co-AAm)/ZnO hydrogel composite, batch adsorption experiments were successfully conducted under different optimised conditions. At last, in-vitro antibacterial activities of Hg2+ loaded GT-cl-(HEMA-co-AAm) and GT-cl-(HEMA-co-AAm)/ZnO were performed in two different well Staphylococcus aureus (gram-positive) and Pseudomonas aeruginosa (gram-negative) bacteria. As a positive control, ampicillin was employed against both types of bacteria. This methodology for the reusability of material has a great ecofriendly impression for minimising secondary waste derived from adsorption and can help design upgraded antibacterial agents.

Enhanced Photo-Catalytic and Antibacterial Properties of Ni-Doped Cd0.9Zn0.1S Nanostructures.

The present work describe the synthesis of Cd0.9Zn0.1S and Cd0.87Zn0.1Ni0.03S nanostructures by chemical co-precipitation method. The XRD profile proved the cubic crystal structure of the samples without any impurity related phases. The reduced size from 63 to 51 Å and the dissimilarities in lattice parameters and micro-strain has been discussed by Ni addition in Cd0.87Zn0.1Ni0.03S structure. The noticed anomalous optical studies and the elevated transmittance at Ni doped sample suggested them for the fabrication of efficient opto-electronic devices. The energy gap reduction during the substitution of Ni = 3% is explained by the generation of extra energy levels associated with defects within the two bands. The release of additional charge carriers, improved optical property, reduced particle size and more defect generation are responsible for the enhanced photo-catalytic performance of Ni doped Cd0.9Zn0.1S. The enhanced anti-bacterial capacity in Cd0.87Zn0.1Ni0.03S is described by the collective response of reduced particle size and higher reactive oxygen species (ROS) like O2 ⋅- , H2O2 and OH ⋅ generating capacity.

Microencapsulation of Cassia fistula Flower Extract with Chitosan and its Antibacterial Studies.

BACKGROUND: The plant used in the present study is Cassia fistula, which belongs to the family Leguminosae and has been used in traditional medicinal systems due to the presence of a copious amount of Phytochemicals with various properties. AIMS: This study is focused on the extraction of phytochemicals from the Cassia fistula flower and its subsequent encapsulation into chitosan matrix for applications in drug delivery. Chitosan is approved by FDA for its use in Pharmaceutical industries. METHODS: As described by several analytical techniques such as FT-IR, NMR, Thermal analysis, and SEM, the microsphere thus prepared by the current study is predicted to release the desired extract with medicinal properties in a controlled manner, allowing for more convenient and desired levels of drug administration. The swelling study and release study of the prepared microsphere have been carried out in physiological pH 2 and 7.4. NMR study has shown that sitosterol and friedelin have been encapsulated successfully into the chitosan matrix. RESULTS: The microspheres have shown up to 80% swelling in pH 2 upto 8 days, and 60% of the in- -vitro controlled drug release has also been found in pH 2 upto 2 days. The thermal studies using TGA and DSC supported the thermal stabilities of CS beads, CFFE and CFFE-CS beads, Also, it showed the dispersion of the CFFE in the cavities of the Chitosan matrix. CONCLUSION: The Biomedical application of the synthesized CFFE-CS beads has also been reported on the basis of their antibacterial studies.

3D printed hydroxyapatite - Zn2+ functionalized starch composite bone grafts for orthopedic and dental applications.

Hydroxyapatite (HA) - polymer composite based 3D printed bone grafts require extensive mechanical and biological property optimization for specific clinical needs. This fuels the need to develop innovative methods of optimization. Using an in-house extrusion-based 3D printer, we show the feasibility of fabricating hydroxyapatite- Zn2+ functionalized starch composites as artificial bone graft substitutes. The experimental procedure for this purpose is fortified with a univariate multi-objective optimization strategy to predict the best composition. The compressive strength of the grafts improves up to ~ 4 folds by parametric optimization and Zn2+ functionalization, without any post-processing. These grafts maintain mechanical integrity and strength during 6 weeks of dissolution study in simulated body fluid (SBF), while the non -functionalized starch-HA grafts fully degrade within a week. The Zn2+ functionalization results in up to ~ 79% antibacterial efficacy against S. aureus. Osteoblast cell viability increases ~ 1.6 folds on these graft surfaces on day 11. Our innovative methods of optimization are expected to reduce the experiment time, cost, and chance of human error in 3D printing. This study redefines the importance of understanding composition and process dependence for making a functionalized 3D printed bone graft for repairing low load-bearing defects such as craniomaxillofacial bone.

Gum mediated synthesis and characterization of CuO nanoparticles towards infectious disease-causing antimicrobial resistance microbial pathogens.

BACKGROUND: In this work biologically active CuO nanoparticle were discussed. The literature suggests that CuO shows very good antibacterial activity on both Gram positive and Gram-negative bacterial strains. Further, it is used in antibacterial coatings on various substrates to prevent various kinds of medical equipment's. Here CuO NPs was prepared via greener approach and almond gum is used as a reducing agent. Almond gum is nontoxic and contains huge amount of polysaccharides. Hence, the gum mediated CuO NPs can be used to treat urinary tract infection (UTI). METHOD: The CuO NPs were characterized using UV, FTIR, XRD and HESEM with EDX analysis. The antibacterial (both Gram positive and Gram negative) effects of CuO NPs were determined with agar well diffusion method. RESULTS: The CuO NPs were characterized by X-ray diffraction pattern result indicates that the monoclinic structure with average crystallite size about 12.91 nm. Straight line model in Scherrer method results found to be crystallite size. The crystallite size and microstrain were estimated in W-H analysis. Lorentz polarization factor, size-strain plot (SSP), morphological index (M-I) and dislocation density were calculated based on x-ray diffraction data. The FTIR analysis confirms presence of Cu and O band. From the absorption spectrum of CuO NPs, it was found to be cutoff wavelength of 230 nm and direct bandgap was found to be 4.97 eV. Morphology analysis shows that the synthesized of CuO NPs reveals agglomerated and spherical in shape. It was found to be 16 nm-25 nm. Energy dispersive spectroscopy (EDX) result indicates percentages of Cu and O element present in the sample. Antimicrobial studies reveal zone of inhibition of CuO NPs. This was used in different pathogens such as gram-positive and Gram-negative bacteria. This study shows exhibit excellent antimicrobial effects of CuO NPs. CONCLUSION: Hence, in this article the novel and cost-effective method to prepare CuO NPs was discussed. The prepared CuO NPs can be used as an antifungal and antibacterial reagent.

Eco-friendly silver nanoparticles (AgNPs) fabricated by green synthesis using the crude extract of marine polychaete, Marphysa moribidii: biosynthesis, characterisation, and antibacterial applications.

The non-hazardous silver nanoparticles (AgNPs) synthesised using the extract of a biological organism has gained widespread attention for various applications, mainly in healthcare. This study aimed at synthesising AgNPs using the aqueous extract of Marphysa moribidii (Annelida, Polychaeta) and to evaluate their antibacterial activities. AgNPs were synthesised in response to silver nitrate (AgNO3) with polychaete crude extract for 24 h incubation; the polychaete crude extract acted as both reducing and stabilising agents. The presence of biosynthesised AgNPs was confirmed by an analysis of colour variations from pinkish to yellowish-brown, as well as the appearance of surface Plasmon resonance (SPR) bands at 398-400 nm using ultraviolet-visible spectroscopy. Biosynthesised AgNPs were characterised by dynamic light scattering, scanning electron microscope, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Biosynthesised AgNPs showed a significant effect (p < 0.05) on Gram-positive bacteria (Staphylococcus aureus and S . epidermidis) and Gram-negative bacteria (Escherichia coli, Klebsiella pnemoniae, Salmonella typhimurium, Serratia sp., Shigella sonnei, and Pseudomonas aeruginosa). Thus, the crude extract of M. moribidii has a potential as a reducing agent for the development of future nanometal-based antibacterial agent, AgNPs, for the treatment of infectious diseases caused by pathogenic bacteria.

Drug-Drug Binary Solids of Nitrofurantoin and Trimethoprim: Crystal Engineering and Pharmaceutical Properties.

With the aim of developing multidrug solids through a tuned crystal engineering approach, we have selected two antiurinary infective drugs, namely, nitrofurantoin (NF) and trimethoprim (TMP) and isolated eight binary drug-drug solid solvates along with a nonsolvated cocrystal. Crystal structure analyses were performed for eight of these solids and rationalized in terms of known supramolecular synthons formed by pyrimidine, imide, and amine functionalities. Notably, the TMP-NF anhydrous cocrystal and its ionic cocrystal hydrate exhibit enhanced equilibrium solubilities compared to pure NF or the simple NF hydrate. Furthermore, the ionic cocrystal hydrate exhibits greater antibacterial activity against the Gram-negative bacteria, E. coli, compared to the parent TMP and NF at the lowest concentration of 3.9 µg/mL. This study indicates initial pathways using the cocrystal methodology that would help to eventually arrive at an antiurinary cocrystal with optimal properties.

Evaluation of Nisin and LL-37 Antimicrobial Peptides as Tool to Preserve Articular Cartilage Healing in a Septic Environment.

Cartilage repair still represents a challenge for clinicians and only few effective therapies are nowadays available. In fact, surgery is limited by the tissue poor self-healing capacity while the autologous transplantation is often forsaken due to the poor in vitro expansion capacity of chondrocytes. Biomaterials science offers a unique alternative based on the replacement of the injured tissue with an artificial tissue-mimicking scaffold. However, the implantation surgical practices and the scaffold itself can be a source of bacterial infection that currently represents the first reason of implants failure due to the increasing antibiotics resistance of pathogens. So, alternative antibacterial tools to prevent infections and consequent device removal are urgently required. In this work, the role of Nisin and LL-37 peptides has been investigated as alternative to antibiotics to their antimicrobial performances for direct application at the surgical site or as doping chemicals for devices aimed at articular cartilage repair. First, peptides cytocompatibility was investigated toward human mesenchymal stem cells to determine safe concentrations; then, the broad-range antibacterial activity was verified toward the Gram-positive Staphylococcus aureus and Staphylococcus epidermidis as well as the Gram-negative Escherichia coli and Aggregatibacter actinomycetemcomitans pathogens. The peptides selective antibacterial activity was verified by a cells-bacteria co-culture assay, while chondrogenesis was assayed to exclude any interference within the differentiation route to simulate the tissue repair. In the next phase, the experiments were repeated by moving from the cell monolayer model to 3D cartilage-like spheroids to revisit the peptides activity in a more physiologically relevant environment model. Finally, the spheroid model was applied in a perfusion bioreactor to simulate an infection in the presence of circulating peptides within a physiological environment. Results suggested that 75 µg/ml Nisin can be considered as a very promising candidate since it was shown to be more cytocompatible and potent against the investigated bacteria than LL-37 in all the tested models.

Anthra[1,2-d][1,2,3]triazine-4,7,12(3H)-triones as a New Class of Antistaphylococcal Agents: Synthesis and Biological Evaluation.

The development and spread of resistance of human pathogenic bacteria to the action of commonly used antibacterial drugs is one of the key problems in modern medicine. One of the especially dangerous and easily developing antibiotic resistant bacterial species is Staphylococcus aureus. Anthra[1,2-d][1,2,3]triazine-4,7,12(3H)-triones 22-38 have been developed as novel effective antistaphylococcal agents. These compounds have been obtained by sequential conversion of 1-amino-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid (1) and 1-amino-4-bromo-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid (2) into the corresponding amides 5-21, followed by subsequent endo-cyclization under the influence of sodium nitrite in acetic acid. Evaluation of the antimicrobial activity of the synthesized compounds against selected species of Gram-positive and Gram-negative bacteria as well as pathogenic yeasts of the Candida genus has been carried out by the serial dilution method. It has been established that anthra[1,2-d][1,2,3]triazine-4,7,12(3H)-triones exhibit selective antibacterial activity against Gram-positive bacteria. Eight, six and seven, out of seventeen compounds tested, effectively inhibited the growth of S. aureus ATCC 25923, S. aureus ATCC 29213 and S. epidermidis ATCC12228, respectively, at a concentration equal to 1 µg/mL or lower. The high antistaphylococcal potential of the most active compounds has been also confirmed against clinical isolates of S. aureus, including the MRSA strains. However, bacteria of the Staphylococcus genus have demonstrated apparent resistance to the novel compounds when grown as a biofilm. None of the four selected compounds 3234 and 36 at a concentration of 64 µg/mL (128 or 256 × MIC-against planktonic cells) has caused any decrease in the metabolic activity of the staphylococcal cells forming the biofilm. The kinetic time-kill assay revealed some important differences in the activity of these substances. Compound 33 is bacteriostatic, while the other three demonstrate bactericidal activity.

Synthesis, characterization and antibacterial study of Ag-Au Bi-metallic nanocomposite by bioreduction using piper betle leaf extract.

Biological reduction method using plant extract for the synthesis of metal and metal oxides are attracted much to the researchers due to its simplicity, which integrates the chemical technology. The special attention is given to the green synthesis of nanoparticles by easily available plants with eco-friendly system compared to other conventional methods. Silver-gold nanocomposite (Ag-Au NCp's) is synthesized by biological reduction of silver nitrate and gold chloride with biological reduction method. These metal salts are simultaneously reduced by betle leaf extract to form respective silver and gold nanocomposite. The structure and morphology of as prepared Ag-Au NCp's sample was characterized by employing powder X-ray diffraction (XRD) tool and by Scanning Electron Micrograph (SEM) tool respectively. Fourier Transform infrared (FTIR) spectral study was undertaken to know the bonding in the prepared silver sample. Energy dispersive X-ray analysis (EDX) study was undertaken to know the formation Ag-Au NCp's. Antibacterial studies are undertaken for the said nanocomposite to know its activity against bacteria.

Synthesis, molecular docking, binding free energy calculation and molecular dynamics simulation studies of benzothiazol-2-ylcarbamodithioates as Staphylococcus aureus MurD inhibitors.

A new series of benzothiazol-2-ylcarbamodithioate functional compounds 5a-f has been designed, synthesized and characterized by spectral data. These compounds were screened for their in vitro antibacterial activity against strains of Staphylococcus aureus (NCIM 5021, NCIM 5022 and methicillin-resistant isolate 43300), Bacillus subtilis (NCIM 2545), Escherichia coli (NCIM 2567), Klebsiella pneumoniae (NCIM 2706) and Psudomonas aeruginosa (NCIM 2036). Compounds 5a and 5d exhibited significant activity against all the tested bacterial strains. Specifically, compounds 5a and 5d showed potent activity against K. pneumoniae (NCIM 2706), while compound 5a also displayed potent activity against S. aureus (NCIM 5021). Compound 5d showed minimum IC50 value of 13.37 µM against S. aureus MurD enzyme. Further, the binding interactions of compounds 5a-f in the catalytic pocket have been investigated using the extra-precision molecular docking and binding free energy calculation by MM-GBSA approach. A 30 ns molecular dynamics simulation of 5d/modeled S. aureus MurD enzyme was performed to determine the stability of the predicted binding conformation.

Influence of Mg Doping on ZnO Nanoparticles for Enhanced Photocatalytic Evaluation and Antibacterial Analysis.

In this research, a facile co-precipitation method was used to synthesize pure and Mg-doped ZnO nanoparticles (NPs). The structure, morphology, chemical composition, and optical and antibacterial activity of the synthesized nanoparticles (NPs) were studied with respect to pure and Mg-doped ZnO concentrations (0-7.5 molar (M) %). X-ray diffraction pattern confirmed the presence of crystalline, hexagonal wurtzite phase of ZnO. Scanning electron microscope (SEM) images revealed that pure and Mg-doped ZnO NPs were in the nanoscale regime with hexagonal crystalline morphology around 30-110 nm. Optical characterization of the sample revealed that the band gap energy (Eg) decreased from 3.36 to 3.04 eV with an increase in Mg2+ doping concentration. Optical absorption spectrum of ZnO redshifted as the Mg concentration varied from 2.5 to 7.5 M. Photoluminescence (PL) spectra showed UV emission peak around 400 nm. Enhanced visible emission between 430 and 600 nm with Mg2+ doping indicated the defect density in ZnO by occupying Zn2+ vacancies with Mg2+ ions. Photocatalytic studies revealed that 7.5% Mg-doped ZnO NPs exhibited maximum degradation (78%) for Rhodamine B (RhB) dye under UV-Vis irradiation. Antibacterial studies were conducted using Gram-positive and Gram-negative bacteria. The results demonstrated that doping with Mg ions inside the ZnO matrix had enhanced the antibacterial activity against all types of bacteria and its performance was improved with successive increment in Mg ion concentration inside ZnO NPs.

Biological and optical properties of sol-gel derived ZnO using different percentages of silver contents.

The role of Ag dopant on ZnO thin films are studied. Ag doped ZnO thin films were deposited by sol-gel dip coating on glass substrates. The X-ray diffraction analysis shows hexagonal wurtzite with preferred orientation along the (101) plane. The crystallite size decreases from 33.40 nm to 28.37 nm with increase in silver doping percentage. Optical examination shows that the band gap decrease with an increase in the Ag doping in ZnO. The structural and optical results prove that Ag has substituted Zn in ZnO lattice. Silver doped ZnO is effective against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria. The roughness and the surface oxygen species accelerate the bacteria killing properties of Ag doped ZnO. They have pharmacological utility as a replacement of the antibiotics, bactericide and disinfectants. The TGA study showed that the thermal stability of the Ag doped ZnO takes place between 380-435 °C.

Design, synthesis, MTT assay, DNA interaction studies of platinum(II) complexes.

The square planar Pt(II) complexes of the type [Pt(Ln)(Cl2)] (where Ln = L1-3 = thiophene-2-carboxamide derivatives and L4-6 = thiophene-2-carbothioamide derivatives) have been synthesized and characterized by physicochemical and various spectroscopic studies. MIC method was employed to inference the antibacterial potency of complexes in reference to free ligands and metal salt. Characteristic binding constant (Kb) and binding mode of complexes with calf thymus DNA (CT-DNA) were determined using absorption titration (0.76-1.61 × 105 M-1), hydrodynamic chain length assay and fluorescence quenching analysis, deducing the partial intercalative mode of binding. Molecular docking calculation displayed free energy of binding in the range of -260.06 to -219.63 kJmol-1. The nuclease profile of complexes towards pUC19 DNA shows that the complexes cleave DNA more efficiently compared to their respective metal salt. Cytotoxicity profile of the complexes on the brine shrimp shows that all the complex exhibit noteworthy cytotoxic activity with LC50 values ranging from 7.87 to 15.94 µg/mL. The complexes have been evaluated for cell proliferation potential in human colon carcinoma cells (HCT 116) and IC50 value of complexes by MTT assay (IC50 = 125-1000 µg/mL).

Antibacterial activity, computational analysis and host toxicity study of thymol-sulfonamide conjugates.

Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococcus faecalis (VRE) are notorious pathogenic multidrug resistant (MDR) bacteria in both hospital and community sectors, and today the first antibacterial drug sulfamethoxazole is ineffective. The monoterpene phenol, thymol was conjugated with seven sulfa drug derivatives individually, adopting the dye-azo synthesis protocol, and conjugates were characterized using spectral analysis techniques such as, UV, FTIR, MS, HPLC, 1H NMR, 13C NMR and SEM. Conjugates were assessed for antibacterial activity in vitro and in silico; the zone of inhibition, MIC and MBC values of each conjugate were determined against isolated MRSA and VRE strains from clinical samples. As 3-dimentional structures of dihydropteroate synthases (DHPSs) of targeted bacteria are not available in protein database, homology models of DHPS enzymes of both bacteria were generated and validated by Ramachandran plots. Seven conjugates were used as ligands in molecular docking against MRSA-DHPS and VRE-DHPS. Additionally bioinformatics tools, PASS prediction, Lipinski rules of five, computational LD50 value, toxicity class, HOMO, LUMO and EPS plots were carried out to assess standard drug-likeliness properties of conjugates. Zone size inhibition of the conjugate, 4b (thymol+sulfadiazine) against MRSA and VRE strains on agar plates were 20 and 40µg/mL as the lowest MIC and MBC values, respectively; while the reference antibiotic ampicillin had the lowest MIC and MBC values at 80 to 180µg/mL. In vitro host-toxicity testing was carried out with cultured human-lymphocytes from umbilical cord blood, and 4b was broadly non-toxic to human cells at 15,000mg/L. Thus, 4b could be promoted a newer antibacterial, against gruesome MDR bacteria.

Synthesis, characterization and antibacterial studies of ruthenium(III) complexes derived from chitosan schiff base.

Chitosan can be modified chemically by condensation reaction of deacetylated chitosan with aldehyde in homogeneous phase. This condensation is carried by primary amine (NH2) with aldehyde (CHO) to form corresponding schiff base. The chitosan biopolymer schiff base derivatives are synthesized with substituted aldehydes namely 4-hydroxy-3-methoxy benzaldehyde, 2-hydroxy benzaldehyde, and 2-hydroxy-3-methoxy benzaldehyde, becomes a complexing agent or ligand. The Ruthenium(III) complexes were obtained by complexation of Ruthenium with schiff base ligands and this product exhibits as an excellent solubility and more biocompatibility. The novel series of schiff base Ruthenium(III) complexes are characterized by Elemental analysis, FT-IR spectroscopy, and Thermo-gravimetric analysis (TGA). The synthesized complexes have been subjected to antibacterial study. The antibacterial results indicated that the antibacterial activity of the complexes were more effective against Gram positive and Gram negative pathogenic bacteria. These findings are giving suitable support for developing new antibacterial agent and expand our scope for applications.

Antibacterial activity of diisocyanate-modified chitosan for biomedical applications.

A diisocyanate-modified chitosan (DIMC) was synthesized via a cross-linking reaction with chitosan and diphenyl methane diisocyanate. The structural and thermal properties of the DIMC were systematically characterized by FTIR, UV-vis, TGA, DSC, XRD and SEM. In addition, the optical properties were evaluated by photoluminescence. Finally, the antibacterial activities of the synthesized DIMC were examined against Escherichia coli and Staphylococcus pyogenes bacteria by agar plate diffusion method. The DIMC showed better degree of bacterial growth inhibition against E. coli as compared with unaltered chitosan. These results suggest that the synthesized chitosan xerogel could be used as a novel biodegradable material with improved antibacterial properties for biomedical applications.