Hydroxychavicol compound was isolated from Piper betle L. leaf and identified via preparative high performance liquid chromatography (Prep-HPLC) and nuclear magnetic resonance (NMR) spectroscopy. Hydroxychavicol compound was demonstrated to be a potential inhibitor for mild steel corrosion in carbon dioxide-containing environments due to the formation of a barrier layer on the steel surface. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results indicated that the inclusion of hydroxychavicol in the aggressive environment made steel surfaces more homogeneous and smoother with a rough mean square roughness of 7.78 nm, whereas the steel surface was severely corroded in the blank solution. Moreover, X-ray photoelectron spectroscopy (XPS) results showed an enrichment of hydroxychavicol species combined with iron oxides and hydroxides on the mild steel surface. This can lead to the creation of a protective layer on the mild steel surface, thereby enhancing corrosion protection and localized inhibition. The work suggested a novel approach to isolate corrosion inhibitors from natural products, particularly agricultural by-products for mild steel in carbon dioxide and chloride ion environment with high inhibition performance.

Reactions at the steel/biogasoline interface trigger the adsorption of 4,4'-[Oxalylbis(imino)]bis(2-hydroxybenzoic Acid) (ODA) layer on the steel surface, thereby activating a mechanism that inhibited the early reactions. Exploring the conditionally deposited ODA layer requires a combined approach, including electrical, optical, and simulation techniques to track the film development and coating characteristics over time, and with the assistance of atomic force microscopy, quantum chemistry (DFT), and molecular dynamics (MD) simulations to reveal the adsorption mechanism of the ODA layer at steel/biogasoline interface. The four experimental ODA concentrations were conducted, related to the simulated un-coverage, undersaturated-, saturated-, and oversaturated-coverage model of the adsorbate on the adsorbent. The EC-RS data examines surface compositions and their distribution, coating/solution interface, and coating/substrate adhesion by, respectively, Raman spectroscopy (RS), electrochemical impedance spectroscopy (EIS), and current density-potential (I-V) scan. Namely, RS pointed out that an organic layer was established when ODA was added to the simulated biogasoline. EIS results revealed insulator behaviors of the ODA layer at the solid-liquid interface, limiting the charge transfer between the steel substrate and the biogasoline. I-V results showed an increase in surface current density and a decrease in surface polarization resistance of the coating with the rise in ODA concentration. The AFM morphology profile verified the degradation of the sample's surface when exposed to biogasoline and the minimization of surface damage by ODA addition through adsorption. The simulation findings revealed that the adsorption of ODA on steel preferred physisorption, reaching the most stable state at a specified temperature and ODA concentration. The adsorption mechanism follows the Generalized Langmuir isotherm. The adsorbate (ODA molecules) can produce a transition phase with the steel substrate surface, which modifies the surface thermodynamic characteristics. The combined electro-optical-simulation technique can be applied to investigate various surface phenomena (reactions, catalyzes, adsorption). It especially helps to understand the protective mechanism of inhibitors in different media.

Waste matter is an abundant source of recyclable materials. This study presented the corrosion inhibitor role of unripe banana peel extract (UBPE) for carbon steel in acidic environments: 1.0 M HCl, 0.5 M H2SO4, and 0.5 M HCl/0.25 M H2SO4. The aim was to demonstrate the robustness of the HCl-UBPE-steel system with respect to competing ions in the solution, and as such, generalizing its mechanism. The localized corrosion in HCl, general corrosion in H2SO4, and their theoretical midpoint were, respectively, subjected to 95.91%, 83.33%, 91.50% corrosion inhibition efficiency when UBPE was added at 3000 ppm. A protective film on the steel surface was found as the cause by electrochemical characterizations and its behavior was explained via protonation of corrosion inhibitor and rust formation on steel surface undering varying acid conditions. Therefore, the work suggests UBPE as corrosion inhibitor for steel in strongly acidic conditions containing chloride and sulfate ions. Highlights center dot Unripe banana peel - water extract (UBPWE) acts as an eco-friendly effective inhibitor for steel in aggressively acidic environments. center dot Carbon steel exhibits more localized corrosion in HCl solution, but more general corrosion in H2SO4 condition. center dot UBPWE performed 95.91, 83.33, and 91.50% of inhibition efficiency for steel in HCl, H2SO4, and mixed conditions. center dot The effective inhibition performance is assigned to the presence of a protective layer on the steel surface. [GRAPHICS] .

Background: Metallic corrosion saps the economy, pollutes the environment, and affects human health and life due to the related toxic chemicals, unwanted reactions, and project collapse, as well as contaminative products. The use of corrosion inhibitors could be a great help to reduce corrosion of metallic materials in severe working conditions. In recent years, natural products have been used for protecting against the corrosion of carbon steel.Methods: Vang tea leaves -water extract (VTLWE) was recommended as a corrosion inhibitor with low-cost and a safe class of material for carbon steel in 1.0 M HCl, 0.5 M H2SO4, and their mixed acidic solutions. VTLWE raw materials were characterized by attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and liquid chromatography-mass spectrometry (LC-MS). Electrochemical properties have been characterized by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PD). Post-immersion surface analyses were also evaluated using scanning electron microscopy (SEM), ATR-FTIR, and X-ray photoelectron spectroscopy (XPS).Significant Findings: The electrochemical data showed that VTLWE posed as a mixed-type inhibitor with more cathodic characteristics and the inhibition effectiveness significantly depended on the VTLWE concentration that increased with an increase of VTLWE in 1.0 M HCl and 0.5 M H2SO4 solutions due to lower corrosion current density and higher polarization resistance. In addition, the results also indicated that 0.5 M H2SO4 solution was more aggressive than 1.0 M HCl solution and was subjected to a higher level of steel corrosion inhibition by VTLWE. Surface analysis results confirmed the occurrence of the organic film layer on the steel surface, assigning to the bonding of functional groups and heteroelements in VTLWE species that were available in investigated solutions. Therefore, the work could add VTLWE as new materials to inhibition systems, giving rise to the du-rable protection against steel corrosion and supplying inspiration in related applications.

Chemical investigation of the lichen Parmotrema indicum Hale led to the isolation of one new diphenyl ether, parmetherine D (1), along with eight known compounds (2-9). The structures were determined by analysis of MS and NMR data and by comparison with the literature. Compounds 1, 2, and 7 were evaluated for α-glucosidase inhibition. Only compound 1 exhibited significant inhibition.[Formula: see text].

The exploration of novel electrocatalysts for CO2 reduction is necessary to overcome global warming and the depletion of fossil fuels. In the current study, the electrocatalytic CO2 reduction of [Re(CO)3Cl(N-N)], where N-N represents 3-(2-pyridyl)-1,2,4-triazole (Hpy), 3-(pyridin-2-yl)-5-phenyl-l,2,4-triazole (Hph), and 2,2'-bipyridine-4,4' dicarboxylic acidic (bpy-COOH) ligands, was investigated. In CO2-saturated electrolytes, cyclic voltammograms showed an enhancement of the current at the second reduction wave for all complexes. In the presence of triethanolamine (TEOA), the currents of Re(Hpy), Re(Hph), and Re(bpy-COOH) enhanced significantly by approximately 4-, 2-, and 5-fold at peak potentials of -1.60, -150, and -1.69 VAg/Ag+, respectively (in comparison to without TEOA). The reduction potential of Re(Hph) was less negative than those of Re(Hpy) and Re(COOH), which was suggested to cause its least efficiency for CO2 reduction. Chronoamperometry measurements showed the stability of the cathodic current at the second reduction wave for at least 300 s, and Re(COOH) was the most stable in the CO2-catalyzed reduction. The appearance and disappearance of the absorption band in the UV/vis spectra indicated the reaction of the catalyst with molecular CO2 and its conversion to new species, which were proposed to be Re-DMF+ and Re-TEOA and were supposed to react with CO2 molecules. The CO2 molecules were claimed to be captured and inserted into the oxygen bond of Re-TEOA, resulting in the enhancement of the CO2 reduction efficiency. The results indicate a new way of using these complexes in electrocatalytic CO2 reduction.

Two previously unreported rotenoids, berectones A and B (1 and 2), along with four known compounds, 3,3 ',4 '-tri-O-methylellagic acid (3), kaempferol (4), 7,4 '-dihydroxy-8-methoxyisoflavone (5), and trans-N-caffeoyltyramine (6) were isolated from the aerial parts of Boerhavia erecta. The structures of all isolated compounds were fully characterized using spectroscopic data, as well as comparison with the previous literature. Compound 6 exhibited the strongest inhibitory activity toward alpha-glucosidase with IC50 value of 4.74 mu M.

Two new phenolic compounds, cristiferides A-B (1-2) together with six known compounds, 2,4-dihydroxyphthalide (3), lecanoric acid (4), orsellinic acid (5), 5-chloroorsellinic acid (6), methyl haematommate (7), and methyl beta-orsellinate (8) were isolated from the lichen Parmotrema cristiferum (Taylor) Hale (Parmeliaceae). The structures of isolated compounds were identified from its spectroscopic data and by comparison with the literatures. Compounds 1-3 and 6-8 were evaluated for alpha-glucosidase inhibition. Compounds 2 and 7 revealed potent activity with IC50 values of 72.66 mu M and 48.73 mu M, respectively.

The self-formation of a porous organic thin-film via corrosion inhibitor supports wide applications of carbon steel in industry. Unfortunately, serious damages could be concentrated to the pinhole and/or pore locations in the porous organic film, resulting in the localized corrosion even when an optimal concentration of organic corrosion inhibitors is used. In this work, SnO2 nanoparticles are used for producing the more robust barrier layer via the self-migration of nanoparticles, resulting in a higher corrosion resistance, smooth and uniform protective layer, as well as the existence of SnO2 in the protective layer that could directly affect the high inhibition performance. Therefore, the work suggests a new way to make a more robust thin film that could extend the use of organic corrosion inhibitors.

Combretum quadrangulare Kurz is widely used in folk medicine in Eastern Asia and is associated with various ethnopharmacological properties including hepatoprotective, antipyretic, analgesic, antidysenteric, and anthelmintic activities. Previous phytochemical investigations reported the presence of numerous triterpenes (mostly cycloartanes, ursanes, lupanes, and oleananes) along with dozens of flavonoids. However, the extracts of C. quadrangulare and isolated flavonoids have not been evaluated for their alpha-glucosidase inhibition. In the frame of our efforts dedicated to the chemical investigation of Vietnamese medicinal plants and their biological activities, a phytochemical study of the MeOH extract of the leaves of C. quadrangulare using bioactive guided isolation was undertaken. In this paper, the isolation and structure elucidation of twelve known compounds, 5-hydroxy-3,7,4′-trimethoxyflavone (1), ayanin (2), kumatakenin (3), rhamnocitrin (4), ombuin (5), myricetin-3,7,3′,5′-tetramethyl ether (6), gardenin D (7), luteolin (12), apigenin (13), mearnsetin (14), isoorientin (15), and vitexin (16) were reported. Bromination was applied to compounds 2 and 3 to provide four new synthetic analogues 8–11. All isolated and synthesized compounds were evaluated for alpha-glucosidase inhibition and antibacterial activity. Compounds 4 and 5 showed moderate antibacterial activity against methicillin-resistant Staphylococcus aureus while others were inactive. All compounds failed to reveal any activity toward extended spectrum beta-lactamase-producing Escherichia coli. Compounds 2, 4, 6–9, and 11–14 showed good alpha-glucosidase inhibition with IC50 values in the range of 30.5–282.0 µM. The kinetic of enzyme inhibition showed that 8 and 11 were noncompetitive type inhibition against alpha-glucosidase. In silico molecular docking model indicated that compounds 8 and 11 were potential inhibitors against enzyme α-glucosidase.

Bioactive-guided phytochemical investigation of Euphorbia antiquorum L. growing in Vietnam led to the isolation of five ent-atisanes, one seco-ent-atisane, and one lathyrane (ingol-type). The structures were elucidated as ent-1α,3α,16β,17-tetrahydroxyatisane (1), ethyl ent-3,4-seco-4,16β,17-trihydroxyatisane-3-carboxylate (2), ent-atisane-3-oxo-16β,17-acetonide (3), ent-3α-acetoxy-16β,17-dihydroxyatisane (4), ent-16β,17-dihydroxyatisane-3-one (5), calliterpenone (6), and ingol 12-acetate (7). Their chemical structures were unambiguously determined by analysis of one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) and high resolution mass spectrometry, as well as by comparison with literature data. Among them, 1 is a new compound while 2 is an ethylated artifact of ent-3,4-seco-4,16β,17-trihydroxyatisane-3-carboxylic acid, a new compound. Isolates were evaluated for alpha-glucosidase inhibition. Compound 3 showed the most significant inhibitory activity against alpha-glucosidase with an IC50 value of 69.62 µM. Further study on mechanism underlying yeast alpha-glucosidase inhibition indicated that 3 could retard the enzyme function by noncompetitive.

Two new cycloartanes, combretanones G and H (1 and 2), were isolated from the leaves of Combretum quadrangulare. Their structures were elucidated by applying a set of spectroscopic methods, while their relative configurations were determined using DFT-NMR chemical shift calculations and subsequent assignment of DP4 probabilities. Compounds 1 and 2 are C-23/C-24 stereoisomers of the previously-reported euphonerin E. Both exhibited moderate cytotoxicity against three human cancer cell lines. Compound 2 was shown to be a potent antiparasitic. Our results confirm the traditional medicinal uses of Combretum quadrangulare in Vietnam.

Nghiên cứu được thực hiện trên lá cây Trâm bầu Combretum quadrangulare Kurz thu hoạch ở tỉnh Long An bằng các phương pháp sắc kí khác nhau. Bốn hợp chất 5-Hydroxy-3,7,4′-trimethoxyflavone (1), ayanin (2), kamatakenin (3), and luteolin (4) được cô lập và xác định cấu trúc hóa học. Cấu trúc hóa học của các hợp chất được xác định bằng các phương pháp phổ nghiệm đồng thời so sánh với các dữ liệu phổ đã được công bố. Hai hợp chất 1 và 4 lần đầu tiên được biết có hiện diện trong cây Trâm bầu.

A new diterpenoid, phyllane C (1), along with three known compounds, ovoideal E (2), spruceanol (3), and fluacinoid B (4) were isolated from the leaves of Phyllanthus acidus growing in Thailand. The structures were determined by analysis of their MS and NMR data as well as by comparison with literature values. DFT-NMR chemical shift calculations and subsequent DP4/DP4+ probability methods were applied to define the relative configuration of 1. Compound 3 showed a weak cytotoxicity against K562 cell line (IC50 41.9 ± 2.31 µg/mL).