Extract of Trema Orientalis (L.) Stem Bark: A Potential Source of Environmentally Friendly Tanning Agent for Leather Industry

Researchers around the world are in continuous endeavor to develop environment friendly tanning agent due to adverse effect of conventionally used chromium during leather tanning. Recent trend of tanning is thus heading to chrome-free and greener chemical processing options. Vegetable tanning is an exoteric leather processing technique because of their lower pollution load on the environment. Considering the inadequacy and high costing for the commercialized tannins, development of alternative tannins from locally available plants and their characterizations are important. In this research, the stem barks of Trema Orientalis (L.) were extracted at different temperatures employing water solvent with or without additives (sodium hydroxide or sodium sulphite) to attain phenolic-rich extractives. To ascertain appropriateness as a vegetable tanning agent, the obtained extracts were thereafter characterized in respect to yield, total phenolic content, tannin content and molecular structure. The extraction yield for all extracts improves and the quality remains nearly unchanged with temperature rising. The elevated concentration of chemical additives enhances the extraction yield but lessens the quality of extracts. In terms of extraction yield and the quality of extracts the best condition for extraction was discerned at 80°C with water solvent. This water extract has a decent extent of phenolic and tannin content of 266.13 mg Gallic acid equivalent/ gm of dry extract and 30.12 % respectively. The final extract exhibits excellent leather retanning tendency comparable to the commercial quebracho tannins.

Selecting optimal parameters for obtaining the extract of red grape pomace

Due to the industrial processing of grapes, large amounts of by-products are produced. The main varieties of by-products are pomace, which is comprised of skins, seeds and any other solid remaining after pressing process and sediments. It is necessary to implement new effective ways of processing to minimize these residues. This problem is relevant for all the wine-producing countries, including Georgia. It is well-known fact that pomace is an important source of phenolic compounds, which are characterized by high antioxidant activity and possess healing-prophylactic properties. It is also worth mentioning that pomace is an easily spoiled product, and without the proper processing, it cannot be stored for a long time. Thus, this research aimed to obtain optimal parameters for extraction, preserving the antioxidant characteristics. The optimal range of the following parameters for extraction was determined: the temperature for drying 45-50 °C, grinding level 1.5 mm, diluent concentration 70% ethanol/water solvent, extraction module 1:20, extraction temperature 50-55 °C, and duration 2 h. This determination of technological parameters of extraction was done according to the best physical-chemical measures and antioxidant activity level. The physical-chemical tests were performed according to the European Union standards. These parameters can produce an extract with distinct antioxidant characteristics that can be used in the food industry as a natural antioxidant. The extract with distinct antioxidant properties was obtained, which can be used in the food industry as a natural antioxidant.

Mono- and Bimetallic Nanoparticles Stabilized by an Aromatic Polymeric Network for a Suzuki Cross-Coupling Reaction

This work addresses the Suzuki cross-coupling between 4-bromoanisole (BrAn) and phenylboronic acid (PBA) in an environmentally benign ethanol–water solvent catalysed by mono- (Pd) and bimetallic (PdAu, PdCu, PdZn) nanoparticles (NPs) stabilised within hyper-cross-linked polystyrene (HPS) bearing tertiary amino groups. Small Pd NPs of about 2 nm in diameters were formed and stabilized by HPS independently in the presence of other metals. High catalytic activity and complete conversion of BrAn was attained at low Pd loading. Introduction of Zn to the catalyst composition resulted in the formation of Pd/Zn/ZnO NPs, which demonstrated nearly double activity as compared to Pd/HPS. Bimetallic core-shell PdAu/HPS samples were 3-fold more active as compared to Pd/HPS. Both Pd/HPS and PdAu/HPS samples revealed promising stability confirmed by catalyst recycling in repeated reaction runs.

Color and antibacterial activity of annatto extracts at various pH of distilled water solvent and extraction temperature

Annato (Bixa orrelana L.) has been renowned as a tropical plant rich in carotenoid pigments such as nonpolar bixin and polar norbixin. This study was aimed to obtain natural colorant and antimicrobials from annatto extracts. The extraction was carried out by maceration for 10 mins using distilled water as the extraction solvent at various pH and extraction temperatures. The variations of solvent pH used in this research were 4, 7, and 9, while that of extraction temperatures were 70, 80, and 90oC. The potential of annatto extract as an antimicrobial agent was tested by analyzing the extract's ability to inhibit pathogens and its phytochemical compounds. Escherichia coli and Staphylococcus aureus were used as the pathogenic bacteria by using the agar diffusion method. The color of annatto extracts was measured using Munsel Chard to determine the level of hue (color), value (brightness), and chroma (intensity), as well as maximum absorbance. The results showed that all extracts have the potential to inhibit E. coli and S aureus (weak-moderate). The observed annatto extracts had different color intensities as indicated by the hue, value, and chroma and a maximum absorbance at a wavelength of 400 nm.

Dynamic Pt-OH-•H2O-Ag Species Mediate Synergetic Electron and Proton Transfer for Catalytic Hydride Reduction of 4-Nitrophenol at Confined Nanoscale Interface

The nature of interfacial state and/or bonding at heterogeneous nanoscale surface of bimetals remains elusive. For very classical probe reaction of catalytic hydride catalytic reduction of –NO2 to NH2 (herein reduction of 4-NP to 4-AP as an example), three abnormal experimental phenomena cannot be elucidated as such: 1) the hydrogen source of final product of 4-AP is originated from water solvent, rather than NaBH4 reducer; 2) reverse electron transfer between bimetals was observed, which is resisted to the normal thermaldynamic law; 3) even in the absence of any metals, for example just using carbon nanodots as supports, the reaction occurs. These observations indicates that the reduction of –NO2 groups did not follow the classical metal-centered electron and hydride transfer mechanism, i.e., Langmuir-Hinshelwood (L-H) mechanism. We herein provide strong evidence that, the catalytic hydride reduction of 4-NP to 4-AP is though a completely new surface hydrous hydroxyl specie mediated concerted electron and proton transfer process, wherein owing to the space overlapping of p orbitals in hydrous hydroxyl intermediate, an ensemble of interface states are dynamically formed, which could be alternative channels for concerted electron and proton transfer. The main role of second metal of Pt is to regulate the density of surface hydrous hydroxyl intermediate and its interactive strength with metals. This new mechanism not only answers all the abnormal experimental observations above mentioned, but also provide some new insights to water and/or hydroxyl group promoted reaction involved the activation of small molecules (CO2, CO, N2, H2O etc.) in areas of electrochemistry, energy storage and metalloenzyme catalysis.

DFT-D4 Insight into the Inclusion of Amphetamine and Methamphetamine in Cucurbit[7]uril: Energetic, Structural and Biosensing Properties

The host–guest interactions of cucurbit[7]uril (CB[7]) as host and amphetamine (AMP), methamphetamine (MET) and their enantiomeric forms (S-form and R-form) as guests were computationally investigated using density functional theory calculations with the recent D4 atomic-charge dependent dispersion corrections. The analysis of energetic, structural and electronic properties with the aid of frontier molecular orbital analysis, charge decomposition analysis (CDA), extended charge decomposition analysis (ECDA) and independent gradient model (IGM) approach allowed to characterize the host–guest interactions in the studied systems. Energetic results indicate the formation of stable non-covalent complexes where R-AMP@CB[7] and S-AMP@CB[7] are more stable thermodynamically than R-MET@CB[7] and S-MET@CB[7] in gas phase while the reverse is true in water solvent. Based on structural analysis, a recognition mechanism is proposed, which suggests that the synergistic effect of van der Waals forces, ion–dipole interactions, intermolecular charge transfer interactions and intermolecular hydrogen bonding is responsible for the stabilization of the complexes. The geometries of the complexes obtained theoretically are in good agreement with the X-ray experimental structures and indicate that the phenyl ring of amphetamine and methamphetamine is deeply buried into the cavity of CB[7] through hydrophobic interactions while the ammonium group remains outside the cavity to establish hydrogen bonds with the portal oxygen atoms of CB[7].

Ru-decorated gallium nitride nanotubes as chemical sensor for detection of purinethol drug: a density functional theory study

We employed density functional B3LYP to inspect the impact of Ru-decoration on a GaN nanotube (GaNNT) sensing performance in detection of purinethol (PT) drug. The interaction of the pristine GaNNT with the PT was found to be weak, and the sensing response is 4.3. Decorating an Ru atom into the GaNNT surface increases the adsorption energy (Ead) of PT from -6.5 to -23.6 kcal/mol. The sensing response significantly rises to 93.6 by Ru-decoration. A short recovery time of 15.7 s is found for the PT desorption from the Ru-decorated GaNNT surface at 298 K. The water solvent reduces Ead of PT to -20.1 kcal/mol. Thus, it suggests that Ru-decorated GaNNT may be a highly sensitive PT sensor with a short recovery time.

Comparative Study on Treatment using Water-based Extract of Fresh and Dry Unripe Banana Peels with Conventional Antibiotics on UTI

Almost every part of a banana plant has use in medicine. Increased bacterial resistance to the conventional antibiotics has led to research into the development of alternative treatments to conventional antibiotics. This study focuses on the antimicrobial properties of banana peels against selected isolates from Urinary Tract Infection sample. The isolates from cultures further analysed with agarose gel electrophoresis for the presence of 16SrRNA and Phylogenetic analysis revealed Staphylococcus sciuri strain, a coagulase‐negative species, Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae and Proteus mirabilis. Fresh unripe and dry unripe were used to determine the antimicrobial activities. A measure of 150grams of both fresh unripe and dry unripe was extracted with 100ml of water solvent (sterile) respectively for about 2days. The solvent extracts were concentrated separately under reduced pressure, 10g of each concentrated solvent extracts were dissolved in 5ml of sterile distilled water and used for antimicrobial assay using agar well diffusion method. The phytochemical analysis of fresh unripe and dry unripe revealed that alkaloid, flavonoid, cardiac glycosids,and phenols were present.. Musa sapientum L peels showed some effect on Escherichia coli, Enterococcusfaecalis, Staphylococcus sciuri, Klebsiellapneumoniae and Proteus mirabilisat 80% concentrations for water. Dry unripe has advantage over fresh unripe banana peels. The peels of Musa sapientum exhibited some inhibitory activity on these selected UTIs isolates, which could be attributed to the presence of certain secondary metabolites. Finally, when compared the peels extracts against the standard antibiotics drugs as the control, the water solvent extract were less effective.

Structure and in silico simulations of a cold-active esterase reveals its prime cold-adaptation mechanism

Here we determined the structure of a cold active family IV esterase (EstN7) cloned from Bacillus cohnii strain N1. EstN7 is a dimer with a classical α/β hydrolase fold. It has an acidic surface that is thought to play a role in cold-adaption by retaining solvation under changed water solvent entropy at lower temperatures. The conformation of the functionally important cap region is significantly different to EstN7's closest relatives, forming a bridge-like structure with reduced helical content providing greater access to the active site through more than one substrate access tunnel. However, dynamics do not appear to play a major role in cold adaption. Molecular dynamics at different temperatures, rigidity analysis, normal mode analysis and geometric simulations of motion confirm the flexibility of the cap region but suggest that the rest of the protein is largely rigid. Rigidity analysis indicates the distribution of hydrophobic tethers is appropriate to colder conditions, where the hydrophobic effect is weaker than in mesophilic conditions due to reduced water entropy. Thus, it is likely that increased substrate accessibility and tolerance to changes in water entropy are important for of EstN7's cold adaptation rather than changes in dynamics.