Development of a green chemistry process for the synthesis of silver nanoparticles has become a focus of interest. This would offer numerous benefits, including ecofriendliness and compatibility for biomedical applications. Here we report the synthesis of silver nanoparticles from the reduction of silver nitrate and an aqueous extract of the lichen Parmotrema praesorediosum as a reductant as well as a stabilizer. The physical appearance of these silver nanoparticles was characterized using ultraviolet-visible spectroscopy, electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction techniques. The results show that silver nanoparticles synthesized using P. praesorediosum have an average particle size of 19 nm with a cubic structure. The antibacterial activity of the synthesized silver nanoparticles was tested against eight micro-organisms using the disk diffusion method. The results reveal that silver nanoparticles synthesized using P. praesorediosum have potential antibacterial activity against Gram-negative bacteria.
A series of benzimidazole-based N-heterocyclic carbene (NHC) proligands {1-benzyl-3-(2-methylbenzyl)-benzimidazolium bromide/hexafluorophosphate (1/4), 1,3-bis(2-methylbenzyl)-benzimidazolium bromide/hexafluorophosphate (2/5) and 1,3-bis(3-(2-methylbenzyl)-benzimidazolium-1-ylmethylbenzene dibromide/dihexafluorophosphate (3/6)} has been synthesized by the successive N-alkylation method. Ag complexes {1-benzyl-3-(2-methylbenzyl)-benzimidazol-2-ylidenesilver(I) hexafluorophosphate (7), 1,3-bis(2-methylbenzyl)-benzimidazol-2-ylidenesilver(I) hexafluorophosphate (8) and 1,3-bis(3-(2-methylbenzyl)-benzimidazol-2-ylidene)-1-ylmethylbenzene disilver(I) dihexafluorophosphate (9)} of NHC ligands have been synthesized by the treatment of benzimidazolium salts with Ag2O at mild reaction conditions. Both, NHC proligands and Ag-NHC complexes have been characterized by (1)H and (13)C{(1)H} NMR and FTIR spectroscopy and elemental analysis technique. Additionally, the structure of the NHC proligand 5 and the mononuclear Ag complexes 7 and 8 has been elucidated by the single crystal X-ray diffraction analysis. Both the complexes exhibit the same general structural motif with linear coordination geometry around the Ag centre having two NHC ligands. Preliminary in vitro antibacterial potentials of reported compounds against a Gram negative (Escherichia coli) and a Gram positive (Bacillus subtilis) bacteria evidenced the higher activity of mononuclear silver(I) complexes. The anticancer studies against the human derived colorectal cancer (HCT 116) and colorectal adenocarcinoma (HT29) cell lines using the MTT assay method, revealed the higher activity of Ag-NHC complexes. The benzimidazolium salts 4-6 and Ag-NHC complexes 7-9 displayed the following IC50 values against the HCT 116 and HT29 cell lines, respectively, 31.8 ± 1.9, 15.2 ± 1.5, 4.8 ± 0.6, 10.5 ± 1.0, 18.7 ± 1.6, 1.20 ± 0.3 and 245.0 ± 4.6, 8.7 ± 0.8, 146.1 ± 3.1, 7.6 ± 0.7, 5.5 ± 0.8, 103.0 ± 2.3 μM.
The fluoroquinolone antibacterial drug ciprofloxacin (cip) has been used to cap metallic (silver and gold) nanoparticles by a robust one pot synthetic method under optimized conditions, using NaBH₄ as a mild reducing agent. Metallic nanoparticles (MNPs) showed constancy against variations in pH, table salt (NaCl) solution, and heat. Capping with metal ions (Ag/Au-cip) has significant implications for the solubility, pharmacokinetics and bioavailability of fluoroquinolone molecules. The metallic nanoparticles were characterized by several techniques such as ultraviolet visible spectroscopy (UV), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) methods. The nanoparticles synthesized using silver and gold were subjected to energy dispersive X-ray tests in order to show their metallic composition. The NH moiety of the piperazine group capped the Ag/Au surfaces, as revealed by spectroscopic studies. The synthesized nanoparticles were also assessed for urease inhibition potential. Fascinatingly, both Ag-cip and Au-cip NPs exhibited significant urease enzyme inhibitory potential, with IC50 = 1.181 ± 0.02 µg/mL and 52.55 ± 2.3 µg/mL, compared to ciprofloxacin (IC50 = 82.95 ± 1.62 µg/mL). MNPs also exhibited significant antibacterial activity against selected bacterial strains.
Several novel 1-[2-(1H-tetrazol-5-yl) ethyl]-1H-benzo[d][1,2,3]triazoles (3a-h) have been synthesized by the condensation of 1-[2-(1H-tetrazol-5-yl)-ethyl]-1H-benzotriazole (2) and appropriate acid chlorides. 1-[2-(1H-tetrazol-5-yl)-ethyl]-1H-benzotriazole (2) was synthesized by reacting 3-(1H-benzo[d][1,2,3]triazol-1-yl)propanenitrile with sodium azide and ammonium chloride in the presence of dimethylformamide. The synthesized compounds were characterized by IR and PMR analysis. The titled compounds were evaluated for their in-vitro antibacterial and antifungal activity by the cup plate method and anticonvulsant activity evaluated by the maximal electroshock induced convulsion method in mice. All synthesized compounds exhibited moderate antibacterial activity against Bacillus subtilis and moderate antifungal activity against Candida albicans. Compounds 5-(2-(1H-benzo[d][1,2,3]triazo-1-yl)ethyl)-1H-tetrazol-1-yl)(4-aminophenyl)methanone 3d and 5-(2-(1 H-benzo[d][1,2,3]triazo-1-yl)ethyl)-1H-tetrazol-1-yl)(2-aminophenyl)methanone 3e elicited excellent anticonvulsant activity.
The leaf extract of a medicinally important plant, watercress (Nasturtium officinale), was obtained through an ultrasound-facilitated method and utilized for the preparation of ZnO nanoparticles via a joint ultrasound-microwave assisted procedure. The characteristics of the extract enriched nanoparticles (Ext/ZnO) were determined by SEM, TEM, XRD, EDX, BET, FTIR, TGA, and UV-Vis DRS analyses and compared to that of ZnO prepared in the absence of the extract (ZnO). The presence of carbon and carbonaceous bonds, changes in the morphology, size, band gap energy, and weight-decay percentage were a number of differences between ZnO and Ext/ZnO that confirmed the link of extract over nanoparticles. Ext/ZnO, watercress leaf extract, ZnO, and insulin therapies were administrated to treat alloxan-diabetic Wister rats and their healing effectiveness results were compared to one another. The serum levels of the main diabetic indices such as insulin, fasting blood glucose, and lipid profile (total triglyceride, total cholesterol, and high-density lipoprotein cholesterol) were estimated for healthy, diabetic, and the rats rehabilitated with the studied therapeutic agents. The watercress extract-enriched ZnO nanoparticles offered the best performance and suppressed the diabetic status of rats. Moreover, both ZnO samples satisfactory inhibited the activities of Staphylococcus aureus and Escherichia coli bacteria. Based on the results, the application of Nasturtium officinale leaf extract can strongly empower ZnO nanoparticles towards superior antidiabetic and enhanced antibacterial activities.
Some novel hydrazone derivatives 6a-o were synthesized from the key intermediate 4-Chloro-N-(2-hydrazinocarbonyl-phenyl)-benzamide 5 and characterized using IR, ¹H-NMR, 13C-NMR, mass spectroscopy and elemental analysis. The inhibitory potential against two secretory phospholipase A₂ (sPLA₂), three protease enzymes and eleven bacterial strains were evaluated. The results revealed that all compounds showed preferential inhibition towards hGIIA isoform of sPLA₂ rather than DrG-IB with compounds 6l and 6e being the most active. The tested compounds exhibited excellent antiprotease activity against proteinase K and protease from Bacillus sp. with compound 6l being the most active against both enzymes. Furthermore, the maximum zones of inhibition against bacterial growth were exhibited by compounds; 6a, 6m, and 6o against P. aeruginosa; 6a, 6b, 6d, 6f, 6l, 6m, 6n, and 6o against Serratia; 6k against S. mutans; and compounds 6a, 6d, 6e, 6m, and 6n against E. feacalis. The docking simulations of hydrazones 6a-o with GIIA sPLA₂, proteinase K and hydrazones 6a-e with glutamine-fructose-6-phosphate transaminase were performed to obtain information regarding the mechanism of action.
This paper describes the fabrication and characterization of bio-nanocomposite hydrogel beads based on Kappa-Carrageenan (κ-Carrageenan) and bio-synthesized silver nanoparticles (Ag-NPs). The silver nanoparticles were prepared in aqueous Citrullus colocynthis seed extract as both reducing and capping agent. Cross-linked κ-Carrageenan/Ag-NPs hydrogel beads were prepared using potassium chloride as the cross-linker. The hydrogel beads were characterized using XRD and FESEM. Moreover, swelling property of the hydrogel beads was investigated. The Ag release profile of the hydrogels was obtained by fitting the experimental data to power law equation. The direct visualization of the green synthesized Ag-NPs using TEM shows particle size in the range of 23±2nm. The bio-nanocomposite hydrogels showed lesser swelling behavior in comparison with pure κ-Carrageenan hydrogel. Regardless the slow Ag release, κ-Carrageenan/Ag-NPs presented good antibacterial activities against Staphylococcus aureus, Methicilin Resistant Staphylococcus aurous, Peseudomonas aeruginosa and Escherichia coli with maximum zones of inhibition 11±2mm. Cytotoxicity study showed that the bio-nanocomposite hydrogels with non-toxic effect of concentration below 1000μg/mL have great pharmacological potential and a suitable level of safety for use in the biological systems.
In recent times, magnesium oxide (MgO) nanoparticles are proven to be an excellent antibacterial agent which inhibits the growth of bacteria by generating reactive oxygen species (ROS). Release of ROS by nanoparticles will damage the cell membrane of bacteria and leads to the leakage of bacterial internal components and cell death. However, chemically synthesized MgO nanoparticles may possess toxic functional groups which may inhibit healthy human cells along with bacterial cells. Thus, the aim of the present study is to synthesize MgO nanoparticles using leaf extracts of Amaranthus tricolor and photo-irradiation of visible light as a catalyst, without addition of any chemicals. Optimization was performed using Box-Behnken design (BBD) to obtain the optimum condition required to synthesize smallest nanoparticles. The parameters such as time of reaction, the concentration of precursor, and light intensity have been identified to affect the size of biosynthesized nanoparticles and was optimized. The experiment performed with optimized conditions such as 0.001 M concentration of magnesium acetate as precursor, 5 cm distance of light (intensity), and 15 min of reaction time (light exposure) has led to the formation of 74.6 nm sized MgO nanoparticles. The antibacterial activities of MgO nanoparticles formed via photo-irradiation and conventional biosynthesis approach were investigated and compared. The lethal dosage of E. coli for photo-irradiated and conventional biosynthesis MgO nanoparticles was 0.6 ml and 0.4 ml, respectively. Likewise, the lethal dosage of S. aureus for both biosynthesis approaches was found to be 0.4 ml. The results revealed that the antibacterial activity of MgO nanoparticles from both biosynthesis approaches was similar. Thus, photo-irradiated MgO nanoparticles were beneficial over heat-mediated conventional method due to the reduced synthesis duration.
This study aimed to develop a novel electrospun polyacrylonitrile (PAN) nanofiber membrane with the enhanced antibacterial property. The PAN nanofiber membrane was first subjected to alkaline hydrolysis treatment, and the treated membrane was subsequently grafted with chitosan (CS) to obtain a CS-modified nanofiber membrane (P-COOH-CS). The modified membrane was then coupled with different dye molecules to form P-COOH-CS-Dye membranes. Lastly, poly(hexamethylene biguanide) hydrochloride (PHMB) was immobilized on the modified membrane to produce P-COOH-CS-Dye-PHMB. Physical characterization studies were conducted on all the synthesized nanofiber membranes. The antibacterial efficacies of nanofiber membranes prepared under different synthesis conditions were evaluated systematically. Under the optimum synthesis conditions, P-COOH-CS-Dye-PHMB was highly effective in disinfecting a high concentration of Escherichia coli, with an antibacterial efficacy of approximately 100%. Additionally, the P-COOH-CS-Dye-PHMB exhibited an outstanding wash durability as its antibacterial efficacy was only reduced in the range of 5%-7% even after 5 repeated cycles of treatment. Overall, the experimental results of this study suggested that the P-COOH-CS-Dye-PHMB is a promising antibacterial nanofiber membrane that can be adopted in the food, pharmaceutical, and textile industries.
A series of novel hybrid heterocycles comprising arylidene thiazolidine-2,4-dione and 1-cyclopropyl-2-(2-fluorophenyl)ethanone were synthesized. These compounds were evaluated for their antimycobacterial activity against Mycobacterium tuberculosis H37Rv in High Throughput Screen. Most of the hybrid arylidene thiazolidine-2,4-diones displayed moderate to good activity with MIC of less than 50 μM. Compound 1m exhibited maximum potency being 5.87 fold more active at EC50 and 6.26 fold more active at EC90 than the standard drug pyrimethamine.
Environment friendly methods for the synthesis of copper nanoparticles have become a valuable trend in the current scenario. The utilization of phytochemicals from plant extracts has become a unique technology for the synthesis of nanoparticles, as they possess dual nature of reducing and capping agents to the nanoparticles. In the present investigation we have synthesized copper nanoparticles (CuNPs) using a rare medicinal plant Cissus arnotiana and evaluated their antibacterial activity against gram negative and gram positive bacteria. The morphology and characterization of the synthesized CuNPs were studied and done using UV-Visible spectroscopy at a wavelength range of 350-380 nm. XRD studies were performed for analyzing the crystalline nature; SEM and TEM for evaluating the spherical shape within the size range of 60-90 nm and AFM was performed to check the surface roughness. The biosynthesized CuNPs showed better antibacterial activity against the gram-negative bacteria, E. coli with an inhibition zone of 22.20 ± 0.16 mm at 75 μg/ml. The antioxidant property observed was comparatively equal with the standard antioxidant agent ascorbic acid at a maximum concentration of 40 μg/ ml. This is the first study reported on C. arnotiana mediated biosynthesis of copper nanoparticles, where we believe that the findings can pave way for a new direction in the field of nanotechnology and nanomedicine where there is a significant potential for antibacterial and antioxidant activities. We predict that, these could lead to an exponential increase in the field of biomedical applications, with the utilization of green synthesized CuNPs, due to its remarkable properties. The highest antibacterial property was observed with gram-negative strains mainly, E. coli, due to its thin peptidoglycan layer and electrostatic interactions between the bacterial cell wall and CuNPs surfaces. Hence, CuNPs can be potent therapeutic agents in several biomedical applications, which are yet to be explored in the near future.
The present study comprises the synthesis of a new series of benzenesulfonamides derived from N-sulfonation of 2-(4-methoxyphenyl)-1-ethanamine (1). The synthesis was initiated by the reaction of 2-(4-methoxyphenyl)-1-ethanamine (1) with benzenesulfonyl chloride (2), to yield N-(4-methoxyphenethyl)benzenesulfonamide (3). This parent molecule 3 was subsequently treated with various alkyl/aralkyl halides (4a-j) in N,N-dimethylformamide (DMF) and in the presence of a weak base lithium hydride (LiH) to obtain various N-(alkyl/aralkyl)-N-(4-methoxyphenethyl) benzenesulfonamides (5a-j). The characterization of these derivatives was carried out by spectroscopic techniques like IR, 1H-NMR, and 13C-NMR. Elemental analysis also supported this data. The biofilm inhibitory action of all the synthesized compounds was carried out on Escherichia coli and some of the compounds were identified to be very suitable inhibitors of this bacterial strain. Furthermore, the molecules were also tested for their cytotoxicity behavior to assess their utility as less cytotoxic therapeutic agents.
Chalcone derivatives have attracted increasing attention due to their numerous pharmacological activities. Changes in their structures have displayed high degree of diversity that has proven to result in a broad spectrum of biological activities. The present study highlights the synthesis of some halogen substituted chalcones 3(a-i) containing the 5-chlorothiophene moiety, their X-ray crystal structures and the evaluation of possible biological activities such as antibacterial, antifungal and reducing power abilities. The results indicate the tested compounds show a varied range of inhibition values against all the tested microbial strains. Compound 3c with a p-fluoro substituent on the phenyl ring exhibits elevated antimicrobial activity, whereas the compounds 3e and 3f displayed the least antimicrobial activities. The compounds 3d, 3e, 3f and 3i showed good ferric and cupric reducing abilities, and the compounds 3b and 3c showed the weakest reducing power in the series.
Silver nanoparticle was synthesized using D-glucosamine chitosan base as green reducing agent at elevated temperature in alkaline pH ranges. The excess of D-glucosamine chitosan base was used as it is both stabilizing and reducing agent at different pHs, regulates the shape and size of the silver nanoparticles. The progressive growth of silver nanoparticles was monitored by UV-Visible spectral studies. A sharp peak at 420 nm indicates the formation of spherical silver nanoparticles. The size and shape of silver nanoparticles were observed from Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) methods. The anisotropically grown nanoparticles were used as probe for Surface Enhanced Raman Studies (SERS) using ATP (4-aminothiophenol) as a model system. The catalytic behavior of silver nanoparticles was exploited for 4-nitrophenol reduction and observed that the reduction reaction follows pseudo first order kinetics with a rate constant 0.65 min. The antibacterial activity of silver nanoparticles was also tested for both gram-positive and -negative microorganisms, in which higher zone of inhibition was observed for gram negative microorganism.
In this study, a series of novel 3-(substituted phenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]isoxazole analogues were synthesized and evaluated for antimycobacterial activity against Mycobacterium tuberculosis (MTB) H(37)Rv and isoniazid resistant M. tuberculosis (INHR-MTB). All the newly synthesized compounds were showing moderate to high inhibitory activities. The compound 6,7-dimethoxy-3-(4-chloro phenyl)-4H-indeno[1,2-c]isoxazole (4b) was found to be the most promising compound, active against MTB H(37)Rv and INHR-MTB with minimum inhibitory concentrations of 0.22 and 0.34 μM.
A new series of N-[5-(4-(alkyl/aryl)-3-nitro-phenyl)-[1,3,4-thiadiazol-2-yl]-2,2-dimethyl-propionamide 4 (a-l) and 6-(4-Methoxy-phenyl)-2-(4-alkyl/aryl)-3-nitro-phenyl)-Imidazo [2,1-b] [1,3,4] thiadiazole 6 (a-l) were synthesized starting from 5-(4-Fluoro-3-nitro-phenyl)-[1,3,4] thiadiazole-2-ylamine. The synthesized compounds were characterized by IR, NMR, mass spectral and elemental analysis. All the compounds were tested for antibacterial and antifungal activities. The antimicrobial activities of the compounds were assessed by well plate method (zone of inhibition). Compounds 4a, 4c and 6e, 6g displayed appreciable activity at the concentration 0.5-1.0 mg/mL.
A series of (E)-1-(4-alkyloxyphenyl)-3-(hydroxyphenyl)-prop-2-en-1-one have been successfully synthesised via Claisen-Schmidt condensation. The synthesised chalcone derivatives consisted of hydroxyl groups at either ortho, meta or para position and differed in the length of the alkyl groups, C (n) H(2) (n) (+1,) where n = 6, 10, 12 and 14. The structures of all compounds were defined by elemental analysis, IR, (1)H- and (13)C-NMR. The antimicrobial studies were carried out against wild-type Escherichia coli American Type Culture Collection 8739 to evaluate the effect of the hydroxyl and the alkyl groups of the synthesised chalcones. All the synthesised compounds have shown significant antimicrobial activities. The optimum inhibition was dependent on the position of the hydroxyl group as well as the length of the alkyl chains.
The immune system is an intricate and coordinated nexus serving as a natural defense to preclude internal and external pathogenic insults. The deregulation in the natural balance of immunological functions as a consequence of either over expression or under expression of immune cells tends to cause disruption of homeostasis in the body and may lead to development of numerous immune system disorders. Chalcone moieties (1,3-diphenyl-2-propen-1-one) have been well-documented as ideal lead compounds or precursors to design a wide range of pharmacologically active agents to down-regulate various immune disorders. Owing to their unique structural and molecular framework, these α, β-unsaturated carbonyl-based moieties have also gained remarkable recognition due to their other multifarious pharmacological properties including antifungal, anti-inflammatory, anti-malarial, antibacterial, anti-tuberculosis, and anticancer potential. Though a great number of methodologies are currently being employed for their synthesis, this review mainly focuses on the natural and synthetic chalcone derivatives that are exclusively synthesized via Claisen-Schmidt condensation reaction and their immunomodulatory prospects. We have critically reviewed the literature and provided convincing evidence for the promising efficacy of chalcone derivatives to modulate functioning of various innate and adaptive immune players including granulocytes, mast cells, monocytes, macrophages, platelets, dendritic cells, natural killer cells, and T-lymphocytes.
In this study, fatty haydroxamic acids (FHAs), which have biological activities as antibiotics and antifungal, have been synthesized via refluxing of triacylglycrides, palm olein, palm stearin or corn oil with hydroxylamine hydrochloride. The products were characterized using the complex formation test of hydroxamic acid group with zinc(I), copper(II) and iron(III), various technique methods including nuclear magnetic resonance ((1)H NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and elemental analysis. Parameters that may affect the conversion of oils to FHAs including the effect of reaction time, effect of organic solvent and effect of hydro/oil molar issue were also investigated in this study. Results of characterization indicate that FHAs were successfully produced from triacylglycrides. The conversion percentages of palm stearin, palm olein and corn oil into their fatty hydroxamic acids are 82, 81 and 78, respectively. Results also showed that hexane is the best organic solvent to produce the FHAs from the three oils used in this study. The optimum reaction time to achieve the maximum conversion percentage of the oils to FHAs was found to be 10 hours for all the three oils, while the optimum molar ration of hydro/to oil was found to be 7:1 for all the different three oils.
Urease is a bacterial enzyme that is responsible for virulence of various pathogenic bacteria such as Staphylococcus aureus, Proteus mirabilis, Klebsiella pneumoniae, Ureaplasma urealyticum, Helicobacter pylori and Mycobacterium tuberculosis. Increased urease activity aids in survival and colonization of pathogenic bacteria causing several disorders especially gastric ulceration. Hence, urease inhibitors are used for treatment of such diseases. In search of new molecules with better urease inhibitory activity, herein we report a series of acridine derived (thio)semicarbazones (4a-4e, 6a-6l) that were found to be active against urease enzyme. Molecular docking studies were carried out to better comprehend the preferential mode of binding of these compounds against urease enzyme. Docking against urease from pathogenic bacterium S. pasteurii was also carried out with favorable results. In silico ADME evaluation was done to determine drug likeness of synthesized compounds.