In order to gain further insight into how various extraction techniques (maceration, microwave-, and ultrasound-assisted extractions) affect the chemical profile and biological activities of leaf extracts from Paeonia tenuifolia L., Paeonia peregrina Mill., and Paeonia officinalis L., this research was performed. The targeted chemical characterization of the extracts was achieved using the Ultra-High-Performance-Liquid-Chromatography-Linear-Trap-Mass-Spectrometry OrbiTrap instrumental technique, while Fourier Transform Infrared Spectroscopy was conducted to investigate the structural properties of the examined leaf extracts. According to the results, the species P. officinalis, Bozurna locality as the origin of the plant material, and microwave-assisted extraction produced the maximum polyphenol yield, (491.9 ± 2.7 mg gallic acid equivalent (GAE)/mL). The ethanolic extracts exhibited moderate antioxidant activity as evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) and phosphomolybdenum tests. With MIC values of 0.125 mg/mL, the leaf extracts produced by ultrasound-assisted extraction and maceration (Deliblato sands and Bogovo gumno) had the best antibacterial activity against Pseudomonas aeruginosa and Salmonella Typhimurium. Ultrasound-assisted extraction has proven to produce the most effective antimicrobial agents. Inhibitory potential towards glucosidase, amylase, cholinesterases, and tyrosinase was evaluated in enzyme inhibition assays and molecular docking simulations. Results show that leaves of P. tenuifolia L. obtained by ultrasound-assisted extraction had the highest acetylcholinesterase and butyrylcholinesterase inhibitory activity. Namely, the complexity of the polyphenol structures, the extraction method, the used locality, and the different mechanisms of the reactions between bioactives from leaf extracts and other components (free radicals, microorganisms, and enzymes) are the main factors that influence the results of the antioxidant tests, as well as the antibacterial and enzyme-inhibitory activities of the extracts. Hydroxymethyl-phenyl pentosyl-hexoside and acetyl-hydroxyphenyl-hexoside were the first time identified in the leaf extract of the Paeonia species. Due to their proven biological activities and the confirmed existence of bioactive compounds, leaf extracts may find use in foodstuffs, functional foods, and pharmaceutical products.
Materials from green resources boast a low carbon footprint, forming the foundation of the circular economy approach in materials science. Thus, in this study, waste poly(ethylene terephthalate) (PET) was subjected to depolymerization using propylene glycol (PG), and subsequent polycondensation with bio-based maleic anhydride (MA) produced unsaturated polyester resin (b-UPR). Bio-derived acryloyl-modified Kraft lignin (KfL-A) served as a vinyl reactive filler in the b-UPR matrix to create b-UPR/KfL-A composites. The structural characterization of KfL-A and b-UPR involved the use of FTIR and NMR techniques. The mechanical properties of the newly fabricated composites were assessed through tensile strength, Vickers microhardness, and dynamic mechanical tests. The addition of KfL-A to the rigid b-UPR matrix enhanced material flexibility, resulting in less stiff and hard materials while preserving composite toughness. For instance, incorporating 10 wt.% of KfL-A in b-UPR led to a 17% reduction in hardness, a 48% decrease in tensile strength, and a 20% reduction in toughness. Positive environmental impact was achieved by incorporation of 64 wt.% of renewable and recycled raw material. Analogously prepared b-UPR/KfL composites showed structural inhomogeneity and somewhat better mechanical properties. Transmission (TEM) and scanning (SEM) electron microscopies revealed a suitable relationship between mechanical and structural properties of composites in relation to the extent of KfL-A addition. The UL94V flammability rating confirmed that flame resistance increased proportionally with the KfL-A addition. Once deposited in a landfill, these composites are expected to disintegrate more easily than PET, causing less harm to the environment and contributing to sustainability in the plastics cycle.
Without being aware of their chemical composition, many cultures have used herbaceous peony roots for medicinal purposes. Modern phytopreparations intended for use in human therapy require specific knowledge about the chemistry of peony roots and their biological activities. In this study, ethanol-water extracts were prepared by maceration and microwave- and ultrasound-assisted extractions (MAE and UAE, respectively) in order to obtain bioactive molecules from the roots of Paeonia tenuifolia L., Paeonia peregrina Mill., and Paeonia officinalis L. wild growing in Serbia. Chemical characterization; polyphenol and flavonoid content; antioxidant, multianti-enzymatic, and antibacterial activities of extracts; and in vitro gastrointestinal digestion (GID) of hot water extracts were performed. The strongest anti-cholinesterase activity was observed in PT extracts. The highest anti-ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical potential was observed in PP extracts, whereas against DPPH (2,2-diphenyl-1-picrylhydrazyl radicals), the best results were achieved with PO extracts. Regarding antibacterial activity, extracts were strongly potent against Bacillus cereus. A molecular docking simulation was conducted to gather insights into the binding affinity and interactions of polyphenols and other Paeonia-specific molecules in the active sites of tested enzymes. In vitro GID of Paeonia teas showed a different recovery and behavior of the individual bioactives, with an increased recovery of methyl gallate and digallate and a decreased recovery of paeoniflorin and its derivatives. PT (Gulenovci) and PP (Pirot) extracts obtained by UAE and M were more efficient in the majority of the bioactivity assays. This study represents an initial step toward the possible application of Paeonia root extracts in pharmacy, medicine, and food technologies.
This paper presents sustainable technology for environmentally friendly composite production. Biobased unsaturated polyester resin (b-UPR), synthesized from waste polyethylene terephthalate (PET) glycosylate and renewable origin maleic anhydride (MAnh) and propylene glycol (PG), was reinforced with unmodified and vinyl-modified biosilica nanoparticles obtained from rice husk. The structural and morphological properties of the obtained particles, b-UPR, as well as composites, were characterized by Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The study of the influence of biosilica modification on the mechanical properties of composites was supported by hardness modeling. Improvement of the tensile strength of the b-UPR-based composite at 2.5 wt.% addition of biosilica modified with vinyl silane, named "b-UPR/SiO2-V" composite, has been achieved with 88% increase. The thermal aging process applied to the b-UPR/SiO2-V composite, which simulates use over the product's lifetime, leads to the deterioration of composites that were used as fillers in commercial unsaturated polyester resin (c-UPR). The grinded artificially aged b-UPR composites were used as filler in c-UPR for the production of a table top layer with outstanding mechanical properties, i.e., impact resistance and microhardness, as well as fire resistance rated in the V-0 category according to the UL-94 test. Developing sustainable composites that are chemically synthesized from renewable sources is important from the aspect of preserving the environment and existing resources as well as the extending their life cycle.
In the study, the optimization of the extraction from Aloe vera leaf waste was performed via varying solid-to-solvent ratio, solvent type, extraction time, and technique (maceration, heat-, ultrasound-, and microwave-assisted extractions-HAE, UAE, and MAE, respectively). The optimal extraction conditions for achieving the highest polyphenol content are a 1:30 ratio, 70% ethanol, and 30 min of HAE. Total flavonoid and protein contents were significantly higher in the extract from MAE, while total condensed tannin content was the highest in HAE. LC-MS analysis quantified 13 anthraquinone and chromone compounds. The variations in the FT-IR spectra of the extracts obtained by different extraction procedures are minor. The influence of extraction conditions on the antioxidant ability of the extracts depended on applied antioxidant assays. The extracts possessed medium inhibition properties against Staphylococcus aureus and weak inhibitory activity against Enterococcus feacalis. The extracts had stimulative effect on HaCaT cell viability. Regarding the extraction yield, there was a significant difference between the used extraction techniques (MAE > HAE > maceration and UAE). The presented study is an initial step in the production of polyphenol-rich extracts from A. vera leaf waste aimed to be used for the potential preparation of pharmaceutical and cosmetic formulations for the skin.
During the last few decades, the requirements for modern machine elements in terms of size reduction, increasing the energy efficiency, and a higher load capacity of standard and non-standard gears have been very prevalent issues. Within these demands, the main goals are the optimization of the gears' tooth profiles, as well as the investigation of new tooth profile designs. The presented design idea is based on the optimal solutions inspired by nature. Special attention is paid to the new design of the tooth root zones of spur gears in order to decrease the stress concentration values and increase the tooth root fatigue resistance. The finite element method is used for stress and strain state calculations, and the particular gear pair is modeled and optimized for these purposes. For tooth root strength analysis, the estimations are based on the theory of critical distances and the stress gradients obtained through finite element analysis. The obtained stress gradients have shown important improvements in the stress distribution in the transition zone optimized by biomimetics. An analysis of the material variation influence is also performed. Based on the investigations of a particular gear pair, a significant stress reduction of about 7% for steel gears and about 10.3% for cast iron gears is obtained for tooth roots optimized by bio-inspired design.
Phenotypic screening of α-substituted thiocarbohydrazones revealed promising activity of 1,5-bis(salicylidene)thiocarbohydrazide against leukemia and breast cancer cells. Supplementary cell-based studies indicated an impairment of DNA replication via the ROS-independent pathway. The structural similarity of α-substituted thiocarbohydrazone to previously published thiosemicarbazone catalytic inhibitors targeting the ATP-binding site of human DNA topoisomerase IIα prompted us to investigate the inhibition activity on this target. Thiocarbohydrazone acted as a catalytic inhibitor and did not intercalate the DNA molecule, which validated their engagement with this cancer target. A comprehensive computational assessment of molecular recognition for a selected thiosemicarbazone and thiocarbohydrazone provided useful information for further optimization of this discovered lead compound for chemotherapeutic anticancer drug discovery.
Multifunctional lignin bio-based adsorbent, b-LMS, was obtained via inverse copolymerization in the suspension of acryloyl modified kraft lignin (KfL-AA) and bio-based trimethylolpropane triacrylate (bio-TMPTA). Morphological and structural characterization of KfL-AA and b-LMS was performed using BET, FTIR, Raman, NMR, TGA, SEM, and XPS techniques. The b-LMS microspheres with 253 ± 42 µm diameters, 69.4 m2 g-1 surface area, and 59% porosity efficiently adsorb Malachite Green (MG), Tartrazine (T), and Methyl Red (MR) dye. The influence of pH, pollutant concentration, temperature, and time on the removal efficiency was studied in a batch mode. Favorable and spontaneous processes with high adsorption capacities e.g. 116.8 mg g-1 for MG, 86.8 mg g-1 for T, and 68.6 mg g-1 for MR indicate the significant adsorptive potential of b-LMS. Results from diffusional and single mass transfer resistance studies indicate that pore diffusion is a rate-limiting step. Theoretical calculations confirmed a higher affinity of b-LMS to cationic dye MG compared with an anionic and neutral one, i.e. T and MR, respectively. The data fitting from a flow system, using semi-empirical equations and Pore Surface Diffusion Modelling (PSDM) provided breakthrough point determination. The results from the desorption and competitive adsorption study proved the exceptional performance of b-LMS. Moreover, sulfation of b-LMS, i.e.production of b-LMS-OSO3H, introduced high-affinity sulfate groups with respect to cationic dye and cations. Developed methodology implements the principle of sustainable development and offers concept whose results contribute to the minimization of environmental pollution.
Coloring Agents , Water Pollutants, Chemical , Coloring Agents/chemistry , Adsorption , Microspheres , Lignin , Water Pollutants, Chemical/chemistry , Kinetics , Cations/chemistry , Models, Theoretical
Highly porous lignin-based microspheres, modified by magnetite nanoparticles, were used for the first time for the removal of selenate anions, Se(VI), from spiked and real water samples. The influence of experimental conditions: selenate concentration, adsorbent dosage and contact time on the adsorption capacity was investigated in a batch experimental mode. The FTIR, XRD, SEM techniques were used to analyze the structural and morphological properties of the native and exhausted adsorbent. The maximum adsorption capacity was found to be 69.9 mg/g for Se(VI) anions at pH 6.46 from the simulated water samples. The modified natural polymer was efficient in Se(VI) removal from the real (potable) water samples, originated from six cities in the Republic of Serbia, with an overage efficacy of 20%. The regeneration capacity of 61% in one cycle of desorption (0.5 M NaOH as desorption solution) of bio-based adsorbent was gained in this investigation. The examined material demonstrated a significant affinity for Se(VI) oxyanion, but a low potential for multi-cycle material application; consequently, the loaded sorbent could be proposed to be used as a Se fertilizer.
Drinking Water , Magnetite Nanoparticles , Water Pollutants, Chemical , Water Purification , Magnetite Nanoparticles/chemistry , Lignin , Selenic Acid , Water Purification/methods , Microspheres , Porosity , Water Pollutants, Chemical/chemistry , Hydrogen-Ion Concentration , Anions
In this work, nanocomposite fibres and microfibres based on alginate and poly(vinyl alcohol) (PVA) with silver nanoparticles (AgNPs) were produced and characterized for potential application as antibacterial wound dressings. PVA/Ag/Na-alginate colloid solution was used for the preparation of the fibres by a simple extrusion technique followed by freezing-thawing cycles. UV-Visible spectroscopy confirmed successful preservation of AgNPs in fibres while Fourier transform infrared spectroscopy has shown a balanced combined effect on the Ca-alginate spatial arrangement with the addition of both AgNPs and PVA. The presence of PVA in fibres induced an increase in the swelling degree as compared with that of Ag/Ca-alginate fibres (approx. 28 versus approx. 14). Still, the initially produced PVA/Ca-alginate fibres were mechanically weaker than Ca-alginate fibres, but after drying and rehydration exhibited better mechanical properties. Also, the obtained fibres released AgNPs and/or silver ions at the concentration of approximately 2.6 µg cm-3 leading to bacteriostatic effects against Staphylococcus aureus and Escherichia coli. These results are relevant for practical utilization of the fibres, which could be stored and applied in the dry form with preserved mechanical stability, sorption capacity and antibacterial activity.
In this study, silicate nanofillers; dicalcium silicate, magnesium silicate, tricalcium silicate, and wollastonite; were synthesized using four different methods and incorporated into the epoxy resin to improve its mechanical properties. Characterization of the newly synthesized nanofillers was performed using Fourier-transformation infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The purpose of this study was to analyze newly developed composite materials reinforced with silicate nanoparticles utilizing tensile testing and a full-field non-contact 3D Digital Image Correlation (DIC) method. Analysis of deformation and displacement fields gives precise material behavior during testing. Testing results allowed a more reliable assessment of the structural integrity of epoxy composite materials reinforced using different silicate nanofillers. It was concluded that the addition of 3% of dicalcium silicate, magnesium silicate, tricalcium silicate, and wollastonite lead to the increasement of tensile strength up to 31.5%, 29.0%, 27.5%, and 23.5% in comparison with neat epoxy, respectively. In order to offer more trustworthy information about the viscoelastic behavior of neat epoxy and composites, a dynamic mechanical analysis (DMA) was also performed and rheological measurements of uncured epoxy matrix and epoxy suspensions were obtained.
In this study, a novel simple and eco-efficient, semi-dry method with a spray system for starch modification has been developed. Compared to conventional semi-dry methods, this method does not use solvents so that no slurry or semi-liquid mixture is obtained, the material is in a moisted/semi-moisted state. The modification of starch was performed using betaine hydrochloride (BHC) as the cationic reagent, and the characteristics of such starch derivates were compared with cationic starches obtained using glycidyltrimethylammonium chloride (GTMAC). Due to the instability, toxicity, and high cost of the most commonly used GTMAC, it should be replaced with more eco-friendly reagents, such as BHC, which is derived from betaine found in most green plants (e.g., spinach - Spinacia oleracea, beets - Beta vulgaris). The influence of processing conditions such as temperature, concentration of cationic reagents, presence and concentration of natural plasticizers/catalyst on physico-chemical and structural properties of cationic starches have also been studied. The cationic degree varied from 0.045-0.204 for the starch-BHC samples and within the range of 0.066-0.245 for the starch-GTMAC samples. The modification of starch with cationic reagents resulted in an increased solubility and swelling capacity, followed by decreased viscosity of the modified starches.
Betaine/chemistry , Green Chemistry Technology/methods , Solvents/chemistry , Starch/chemistry , Cations/chemistry , Epoxy Compounds/chemistry , Plants/chemistry , Quaternary Ammonium Compounds/chemistry , Solubility , Viscosity
Silica particles were obtained from rice husk to which layered double hydroxide particles were deposited (weight ratio 1 : 1). Fe2+-Al3+ layered double hydroxides (FeAl-LDH) were synthesized by co-precipitation with ratios Fe : Al of 3 : 1 in the presence of SiO2 particles from the rice husk. Characterization of the synthesized FeAl-LDH@SiO2 particles was performed by X-ray diffraction, Fourier transforms infrared spectroscopy (FTIR) and scanning electron microscopy with EDS. Prepared FeAl-LDH@SiO2 particles were used as reinforcing agents in 1, 3 and 5 wt% quantity in poly (methyl) methacrylate matrix. The aim of this study was to examine whether FeAl-LDH@SiO2 particles affect the mechanical properties of polymer composite materials. The morphology of the composites was examined using a field emission scanning electron microscope. Microindentation, tensile and impact testing determined the mechanical properties of the obtained composites.
The alkali treated subglebal tissue of the mosaic puffball (Handkea utriformis) (Sa) and Sa modified with hydroxyapatite (Sa-HAp), obtained by successive ionic layer adsorption and reaction (SILAR) method, were used for the removal of Pb2+, Cd2+ and Ni2+ from aqueous solution. The materials were characterized by FT-IR, Raman, SEM and EDS analysis and by determination of pHPZC. The adsorption performances of Sa and Sa-HAp were assessed in batch experiments at different pH, contact times, temperatures and mass of the adsorbent. Different models of adsorption isotherms were used, and the best fit was obtained with the Langmuir model. Maximum adsorption capacities of Sa towards Pb2+, Cd2+ and Ni2+ were 44.82, 15.54 and 17.21 mg g-1, while for Sa-HAp were 79.55, 52.59 and 45.01 mg g-1, respectively. Kinetic data were well fitted by a pseudo second-order model, while thermodynamic studies disclose spontaneous and endothermic adsorption process. The Sa-Hap was successfully regenerated with 1 M NaCl and after the fifth desorption cycle and 10 h achieved 82.9, 69.7 and 60.4 %, while for 0.5 M NaCl + 0.5 M NaOH and 1 h was 78.3, 64.1, 57.5 % of desorbed Pb2+, Cd2+ and Ni2+, respectively. The competitive study and results from a column system confirmed good applicability of Sa-HAp adsorbent.
Agaricales , Metals, Heavy , Water Pollutants, Chemical , Adsorption , Hydrogen-Ion Concentration , Kinetics , Solutions , Spectroscopy, Fourier Transform Infrared , Thermodynamics , Water Pollutants, Chemical/analysis
The goal of this study was to investigate the effect of the structure of Mn-Al layered double hydroxide (LDH) on the adhesion behavior of composite adhesives on two Al alloys (L3005 and L8079). The composite adhesives were made out of the UV-curing Bisphenol A glycidylmethacrylate/triethylene glycol dimethacrylate (BT) as polymer matrix and the addition of 1, 3, and 5 wt. % of Mn-Al LDH as adhesion enhancers. Adhesion was evaluated by using the micro Vickers hardness testing procedure. The wetting angle of composite adhesives to the Al substrates was measured and compared to the adhesion parameter b obtained from the microhardness tests. The highest increase in adhesion was observed for BT with 5 wt. % of Mn-Al LDH on L3005 substrate, which was more than 15 times higher than the adhesion for the neat BT. The morphological segregation of composite adhesives after the contact with Al substrates was examined by optical microscopy and a higher compatibility of Mn-Al LDH particles with L3005 substrate was found. The methods used for the adhesion properties assessment suggested that the Mn-Al LDH was the best adhesion enhancer of the BT matrix for L3005 substrate containing a higher content of Mn and surface hydroxyl groups.
In this study, Lactobacillus reuteri B2 was isolated from the feces of C57BL/6 mice and assessed on probiotic activity. L. reuteri B2 was identified by 16S rDNA sequencing, which the cell viability in acidic conditions at pH 2.0 was 64% after 2 h, and in the presents of 0.30% of the bile salts, after 6 h, was 37%. Antimicrobial assay with L. reuteri B2 showed maximum diameters against Klebsiela oxytoca J7 (12.5 ± 0.71 mm). We further hypothesized if L. reuteri B2 strain in the free form can survive all conditions in the gastrointestinal tract (GIT) then the utilization of the appropriate biomaterials would ameliorate its stability and viability in GIT. L. reuteri B2 was microencapsulated into sodium alginate-(Na-alg) and different content of Na-alg and sodium maleate (SM) beads. Characterization materials enveloped their thermal characteristics (TGA/DTA analysis) and structure using: scanning electron microscopy (SEM), FTIR, and particle size distribution. The high survival rate of L. reuteri B2 at low pH from 2.0 to 4.0 and in the presence of the bile salts, at concentrations up to 0.30%, was obtained. L. reuteri B2 showed strong antimicrobial activity and the best protection microencapsulated with Na-alg + SM in simulated gastric juices (SGJ).
Alginates/chemistry , Biopolymers/chemistry , DNA, Ribosomal/metabolism , Limosilactobacillus reuteri/metabolism , Probiotics/therapeutic use
Electronic interactions in donor-π-linker-acceptor systems with barbituric acid as an electron acceptor and possible electron donor were investigated to screen promising candidates with a push-pull character based on experimental and quantum chemical studies. The tautomeric properties of 5-benzylidenebarbituric acid derivatives were studied with NMR spectra, spectrophotometric determination of the pKa values, and quantum chemical calculations. Linear solvation energy relationships (LSER) and linear free energy relationships (LFER) were applied to the spectral data - UV frequencies and 13C NMR chemical shifts. The experimental studies of the nature of the ground and excited state of investigated compounds were successfully interpreted using a computational chemistry approach including ab initio MP2 geometry optimization and time-dependent DFT calculations of excited states. Quantification of the push-pull character of barbituric acid derivatives was performed by the 13CNMR chemical shift differences, Mayer π bond order analysis, hole-electron distribution analysis, and calculations of intramolecular charge transfer (ICT) indices. The results obtained show, that when coupled with a strong electron-donor, barbituric acid can act as the electron-acceptor in push-pull systems, and when coupled with a strong electron-acceptor, barbituric acid can act as the weak electron-donor.
A simple sol-gel method and external gelatinization method of hollow alumina spheres synthesis were developed in this study. The spheres were modified with polyethyleneimine (PEI) producing PEI-Al2O3 via (3-glycidyloxypropyl)trimethoxy-silane, GLYMO, linker. Characterization results, obtained using XRD and SEM microscopy revealed spherical geometry with a hollow core of PEI-Al2O3 adsorbent. Introduction of a large number of the amino group, 6.9 mmol g-1, contributes to achieving high adsorption capacities, qm, of 95.6, 124.9, 61.3, and 125.9 mg g-1 for Cd2+, Pb2+, As(V), and DCF, respectively, which is obtained by using the Langmuir model. Thermodynamic studies indicated feasible adsorption and higher spontaneity with temperature increase. The kinetic study conveniently modeled using pseudo-second-order (PSO) and Weber-Morris kinetic model, as well as single resistance mass transfer model, indicated a change of the contribution of diffusional processes during adsorption with a dominance of intra-particle diffusion. The fixed-bed column adsorption data, fitted using Bohart-Adams, Clark, Yoon-Nelson, and Thomas models, showed lower capacity in comparison to batch study, and thus clear potential applicability of PEI-Al2O3 was deduced even at a high loading of feed water.
Water Pollutants, Chemical , Water Purification , Adsorption , Aluminum Oxide , Cadmium , Diclofenac , Hydrogen-Ion Concentration , Kinetics , Lead , Water Pollutants, Chemical/analysis
In this study we synthesized a series of sixteen bis(imino)pyridines (BIPs) starting from 2,6-diaminopyridine and various aromatic aldehydes, and evaluated their antioxidant, antibacterial, antifungal and acetylcholinesterase (AChE) inhibitory activity. The chemical structures were elucidated by FTIR, elemental analysis, ESR and HRMS. 1H and 13C NMR spectra couldn't be acquired due to the formation of stable, carbon-centered radical cations in a solution, as confirmed by ESR spectroscopy and DFT calculations. The in vitro antioxidant potency was evaluated using four assays: free radical scavenging activity (DPPH and ABTS), reducing power and total antioxidant capacity assay. BIPs demonstrated excellent antioxidant properties, and two derivatives proved to be more potent than reference antioxidants (ascorbic acid and Trolox) in all assays. DFT calculations on ωB97XD/6-311++g(d,p) level of theory provided valuable insights into the radical scavenging mechanism of BIPs. For hydroxyl-substituted BIPs, hydrogen atom transfer (HAT) is a predominant mechanism, while the single electron transfer coupled with proton transfer (SET-PT) governs the antioxidant activity of other derivatives. Intramolecular hydrogen bonding (IHB) plays an important role in the mechanism of antioxidant activity as revealed by noncovalent interaction analysis and rotational barrier calculations. The spin density of radical cations is localized on carbon atoms of a pyridine ring, which corroborates with g-factors and multiplicity obtained from ESR analysis. The most potent BIP exhibited moderate inhibitory activity toward AChE (IC50 = 20 ± 4 µM), while molecular docking suggested binding at the peripheral anionic site of AChE with the MMFF94 binding enthalpy of -43.4 kcal/mol. Moderate in vitro antimicrobial activity of BIPs have been determined against several pathogenic bacterial strains: Pseudomonas aeruginosa, Escherichia coli, Enterococcus faecalis, Staphylococcus aureus and clinical isolate of methicillin resistant S. aureus (MRSA). The antifungal activity of BIPs toward Candida albicans was also confirmed. The similarity ensemble approach combined with molecular docking suggested leucyl aminopeptidase as the probable antimicrobial target for the three most potent BIP derivatives.
Anti-Infective Agents/therapeutic use , Antifungal Agents/therapeutic use , Antioxidants/therapeutic use , Cholinesterase Inhibitors/therapeutic use , Electron Spin Resonance Spectroscopy/methods , Pyridines/chemical synthesis , Pyridines/therapeutic use , Candida albicans , Humans , Pyridines/pharmacology , Structure-Activity Relationship
The controllable synthesis of rutile TiO2 single crystal particles with the preferential orientation of {111} facets still remains a scientific and technological challenge. Here, we developed a facile route for fabrication of rutile TiO2 nanorod crystals (RTiO2NRs) having high ratios of oxidative {111} to reductive {110} surfaces. RTiO2NRs were synthesized using a peroxo-titanium complex (PTC) approach, which was controlled by changing the Ti/H2O2 ratio. The thus obtained RTiO2NRs revealed a high tendency to agglomerate through orientation-dependent attachment along the {110} facets. This resulted in an increased {111}/{110} surface ratio and led to a markedly improved photocatalytic activity of RTiO2NR aggregates. The reported findings illustrate the rich potential of the herein proposed facile and energy-efficient synthesis of nanostructured rutile TiO2-based photocatalysts.
