Search Results (86)

The increasing resistance of pathogens to conventional antibiotics has necessitated the search for novel antimicrobial agents from medicinal plants. Nelsonia canescens—a plant traditionally used in Africa and Asia for the management of health issues, such as viral infections, cardiovascular diseases, and inflammation—has been reported to demonstrate antimicrobial activity and has been investigated for its bioactive constituents. The whole plant was collected, air-dried, and extracted using 70% methanol. The crude methanol extract was partitioned into hexane, chloroform, ethyl acetate, and butanol fractions. The ethyl acetate fraction was subjected to column chromatography and gel filtration, leading to the isolation of a compound coded A₁. The structure of compound A₁ was established through UV, FTIR, NMR (¹H, ¹³C, DEPT, COSY, HMQC, and HMBC), and chemical tests. Compound A₁ was identified as a 2*-hydroxy-4*-phenyl-(2**-hydroxy-ethyl)-3′-(4′′′→1′′) glucose-rhamnose-3-hydroxy phenyl ester, a flavonoid derivative. A spectral analysis confirmed its structure, with key signals including olefinic protons (δ 6.30 and 7.62) in the trans-configuration, aromatic protons, and sugar moieties. The compound exhibited a melting point of 105–107 °C and was partially soluble in chloroform but fully soluble in methanol, suggesting that the compound is highly polar in nature. This is the first report on the isolation of the 2*-hydroxy-4*-phenyl-(2**-hydroxy-ethyl)-3′-(4′′′→1′′) glucose-rhamnose-3-hydroxy phenyl ester from Nelsonia canescens, contributing to the taxonomy of the plant. The compound’s structural features suggest potential bioactive properties, warranting further investigation into its pharmacological applications through in vitro and molecular docking studies. Full article

This study investigates the antioxidant properties of aucubin (AU), an iridoid compound, focusing on its ability to scavenge hydroxyl radicals (^•OH) through its hydroxyl functional groups. Gaussian software was employed to model and validate the underlying antioxidant reaction mechanisms. Three primary pathways were examined: hydrogen atom transfer (HAT), sequential electron transfer-proton transfer (SET-PT), and sequential proton loss–electron transfer (SPLET). All calculations were performed using the M06-2X functional within density functional theory (DFT) at the def2-TZVP level, incorporating Grimme’s D3 dispersion correction and the implicit solvation model based on solute electron density (SMD) for water. Various thermodynamic parameters were determined to analyze and compare the antioxidant reactions, including the O-H bond dissociation energy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), electron transfer enthalpy (ETE), and proton affinity (PA) of the hydroxy groups. The results indicated that the HAT mechanism is the dominant pathway in the scavenging of ^•OH radicals by AU. The key active sites were identified as the 6-OH group in the aglycone structure and the 6′-OH group in the sugar moiety. Moreover, the polar aqueous environment promoted O-H bond homolysis to enhance the antioxidant activity. Full article

4,4’-Methylenebis(N,N-diglycidylaniline) (AG80), as a high-performance thermosetting material, holds significant application value due to the enhancement of its strength, toughness, and thermal stability. However, conventional toughening methods often lead to a decrease in material strength, limiting their application. Modification of AG80 epoxy resin was performed using hydroxy-terminated polyphenylpropylsiloxane (Z-6018) and a self-synthesized epoxy compatibilizer (P/E30) to regulate the phase structure of the modified resin, achieving a synergistic enhancement in both strength and toughness. The modified resin was characterized by Fourier transform infrared analysis (FTIR), proton nuclear magnetic resonance (¹H NMR) spectroscopy, silicon-29 nuclear magnetic resonance (²⁹Si NMR) spectroscopy, and epoxy value titration. It was found that the phase structure of the modified resin significantly affects mechanical properties. Thus, P/E30 was introduced to regulate the phase structure, achieving enhanced toughness and strength. At 20 wt.% P/E30 addition, the tensile strength, impact strength, and fracture toughness increased by 50.89%, 454.79%, and 152.43%, respectively, compared to AG80. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses indicate that P/E30 regulates the silicon-rich spherical phase and interfacial compatibility, establishing a bicontinuous structure within the spherical phase, which is crucial for excellent mechanical properties. Additionally, the introduction of Z-6018 enhances the thermal stability of the resin. Full article

Previously, we have described a successful molecular switch (8-(benzo[d]thiazol-2-yl)quinolin-7-ol), working on the basis of long-range proton transfer. Bearing in mind that its switching efficiency in low-polarity aprotic solvents is not sufficient, in the current communication, we investigate in detail the effect of the substitution in the benzothiazole ring. By using the DFT approach, the ground-state stability of the tautomeric forms, involved in the switching process, is modeled with the aim of finding conditions where clean switching could be possible in variety of aprotic solvents. The results indicate that the substitution with electron-acceptor substituents could increase the switching efficiency, but the overall improvement depends on the positions and electronic effect of the particular substituent. Full article

Cannabinoid molecules are the family of molecules that bind to the cannabinoid receptors (CB1 and CB2) of the human body and cause changes in numerous biological functions including motor coordination, emotion, and pain reception. Cannabinoids occur either naturally in the Cannabis Sativa plant or can be produced synthetically in the laboratory. The need for accurate analytical methods for analyzing cannabinoid molecules is of considerable current importance due to demands for detecting illegal cannabinoids and for monitoring the manufacture of popular, non-illegal cannabinoid products. Mass spectrometry has been shown to be an optimum technique for identifying cannabinoids. In this work, we perform Higher Collisional Dissociation (HCD) mass spectrometric measurements on an Orbitrap Fusion Tribrid Mass Spectrometer to measure the collision-energy-dependent molecular fragmentation pathways of a group of key cannabinoids and their metabolites (cannabidiol, Δ9-Tetrahydrocannabinol, 11-Hydroxy-Δ9-tetrahydrocannabinol, 11-nor-9-Carboxy-Δ9-tetrahydrocannabinol, cannabidiolic acid, tetrahydrocannabinolic acid), along with two synthetic cannabinoids (JWH-018 and MDMB-FUBINACA). This is the first time that cannabinoid molecules have been studied using energy-resolved HCD methods. We identified a number of common, primary fragmentation pathways, including loss of water, loss of other small neutral molecule units (e.g., butene), and rupture of the central C-C bond that links the aromatic and alkyl ring groups. Quantum chemical calculations are presented to provide insights into preferred protonation sites and to characterize isomerization of protonated open-ring cannabinoids (e.g., [CBDA + H]⁺) into closed-ring analogues (e.g., [THCA + H]⁺). A key result to emerge from our study is that energy-resolved HCD measurements are particularly valuable in identifying isomerization, since the isobaric pairs of molecular ions studied here (e.g., [CBDA + H]⁺ and [THCA + H]⁺) are associated with identical HCD profiles indicating that isomerization of one structure into the other has occurred during the electrospray–mass spectrometry process. This is an important result as it will have general applicability to other tautomeric ions and thus demonstrates the application of energy-resolved HCD as a tool for identifying tautomerization proclivity. Full article

Complete assignments of the ¹H and ¹³C NMR chemical shifts for the monoterpenes, borneol 1a and isoborneol 2a, as well as their derivatives (1b–1g and 2b–2g), in which the secondary hydroxy group is protected with various protecting groups, have been made in various solvents. Upon protection of the hydroxy groups in 1a and 2a, many protons and carbons within the bicyclic ring exhibited downfield or upfield shifts in their chemical shift values, facilitating the unambiguous assignments of these protons and carbons. These chemical shift values also showed excellent correlations with those obtained from density functional theory (DFT) calculations. Furthermore, the anisotropic effect of the benzene ring was estimated by the analysis of the iso-chemical shielding surface (ICSS) resulting from substituents introduced to the hydroxyl groups of 1a and 2a. Full article

The chalcone derivatives with hydroxy group (2) have been examined using low-temperature fluorescence spectroscopy. The study aimed to freeze the intramolecular charge transfer (ICT) motion in order to reveal the potential hidden transition(s) that are difficult to observe at room temperature. Although chalcone 2 revealed one emission peak at ~667 nm at room temperature, it exhibited two emission peaks (λ_em = 580 and 636 nm) in EtOH at liquid N₂ temperatures (77 K). With the aid of model compound 3 with methoxy group and aluminum complex 2-Al³⁺, attempts were made to assign these emission peaks. The results point towards the possibility of the coexistence of ICT and excited state intramolecular proton transfer (ESIPT) in the chalcone derivatives with extended conjugation. Full article

New cyclotriphosphazene derivatives featuring amide–Schiff base linkages with a hydrazine bridge and different terminal ends, such as decyl alkyl chains and hydroxy groups, were successfully synthesized and characterized. Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and CHN elemental analysis were used to characterize the structures of these compounds. The formation of hydrazine-bridged cyclotriphosphazene derivatives with amide–Schiff base linkages was confirmed by the FTIR spectra, showing a primary amine band for the amide linkage around ~3300 cm⁻¹ and a band for the Schiff base linkage near ~1595 cm⁻¹. This was further supported by NMR analysis, which displayed an amide proton (H-N-C=O) at ~δ 10.00 ppm and an azomethine proton (H-C=N) within the δ 8.40–8.70 ppm range. The ³¹P NMR spectra of cyclotriphosphazene compounds display a singlet at ~δ 8.20 ppm, indicating an upfield shift that suggests the complete substitution of all phosphorus atoms with identical side chains. Furthermore, CHN analysis verified the purity of the synthesized compounds, with a percentage error below 2%. The introduction of hydrazine bridges and amide–Schiff base linkages into the cyclotriphosphazene core significantly enriches the molecular structure with diverse functional groups. These modifications not only improve the compound’s stability and reactivity, but also expand its potential for a wide range of applications. Full article

Long-range proton transfer in several conjugated proton cranes, originating from 7-hydroxy quinoline as a proton transfer platform, has been investigated theoretically by means of DFT and TD-DFT methodology. Major emphasis was given to their applicability to provide clean switching upon irradiation. The border conditions require the existence of a single enol tautomer in the ground state, which under excitation through a series of consecutive exited and ground state intramolecular proton transfer steps is transferred to the keto tautomer. It was shown that the most suitable candidates are based on using iso-quinoline, pyrimidine and 4-nitropyridine as proton crane units. Their suitability is a function of aromaticity changes, the basicity of the nitrogen atom from the proton crane unit and the structural effects originating from their conjugation with 7-hydroxy quinoline. Full article

Protection of the hydroxy group in monoterpenoids borneol and isoborneol with various silyl-protective groups containing a different number of phenyl groups enabled complete assignments of the ¹H chemical shifts. In particular, a wider range of the protons in isoborneol and its silyl-protected derivatives were influenced than those in borneol and its silyl-protected derivatives, which is likely to be due to the anisotropic effects from the phenyl groups. Understanding these effects allows for the interpretation of the ¹H NMR spectra and provides information about how silyl-protecting groups affect these spectra. Full article

Complete assignments of the ¹H NMR chemical shifts for monoterpenes, borneol, and isoborneol, and their derivatives in which the secondary hydroxy group is protected with an acetyl group or a benzoyl group, have been made in CDCl₃ and C₆D₆. Upon the protection of the hydroxy group with the carbonyl functional groups, or acetyl or benzoyl groups, many protons constituting the bicyclic ring exhibited downfield and upfield shifts in the chemical shift values, aiding in the unambiguous assignments of protons and carbons. Full article

Atopic dermatitis (AD) is a common inflammatory skin disease, in particular among infants, and is characterized, among other things, by a modification in fatty acid and ceramide composition of the skin’s stratum corneum. Palmitic acid and stearic acid, along with C₁₆-ceramide and 2-hydroxy C₁₆-ceramide, occur strikingly in AD. They coincide with a simultaneous decrease in very long-chain ceramides and ultra-long-chain ceramides, which form the outermost lipid barrier. Ceramides originate from cellular sphingolipid/ceramide metabolism, comprising a well-orchestrated network of enzymes involving various ELOVLs and CerSs in the de novo ceramide synthesis and neutral and acid CERase in degradation. Contrasting changes in long-chain ceramides and very long-chain ceramides in AD can be more clearly explained by the compartmentalization of ceramide synthesis. According to our hypothesis, the origin of increased C₁₆-ceramide and 2-hydroxy C₁₆-ceramide is located in the lysosome. Conversely, the decreased ultra-long-chain and very long-chain ceramides are the result of impaired ELOVL fatty acid elongation. The suggested model’s key elements include the lysosomal aCERase, which has pH-dependent long-chain C₁₆-ceramide synthase activity (revaCERase); the NADPH-activated step-in enzyme ELOVL6 for fatty acid elongation; and the coincidence of impaired ELOVL fatty acid elongation and an elevated lysosomal pH, which is considered to be the trigger for the altered ceramide biosynthesis in the lysosome. To maintain the ELOVL6 fatty acid elongation and the supply of NADPH and ATP to the cell, the polyunsaturated PPARG activator linoleic acid is considered to be one of the most suitable compounds. In the event that the increase in lysosomal pH is triggered by lysosomotropic compounds, compounds that disrupt the transmembrane proton gradient or force the breakdown of lysosomal proton pumps, non-HLA-classified AGEP may result. Full article

Human exposure to PM2.5 and PM10 has been linked to respiratory and cardiovascular diseases through inflammation activation. The kynurenine pathway is associated with inflammation, and it is necessary to investigate the effects of long-term PM2.5 and PM10 exposure on this pathway. This study aimed to conduct a cross-sectional analysis of long-term PM2.5 and PM10 exposure’s impact on the kynurenine pathway using proton NMR spectroscopy (¹H-NMR). The participants were divided into a low-PM-exposure group (LG; n = 98), and a high-PM-exposure group (HG; n = 92). The metabolites of tryptophan were determined in blood by ¹H-NMR. Serotonin, cinnabarinic acid, xanthurenic acid, 5-hydroxytryptophan, indoleacetic acid, tryptamine, melatonin, L-tryptophan, 5-hydroxy-L-tryptophol, indoxyl, 2-aminobenzoic acid, 5-HTOL, hydroxykynurenine, L-3-hydroxykynurenine, N-formyl kynurenine, 3-hydroxy anthranilic acid, kynurenic acid, and picolinic acid significantly increased (p < 0.05) in the HG group. Conversely, NAD and quinolinic acid significantly decreased in the HG group compared to the LG group. The enzyme activities of indoleamine 2,3-dioxygenase and formamidase significantly decreased, while kynureninase and kynurenine monooxygenase significantly increased. The kynurenine pathway is linked to inflammation and non-communicable diseases. Disruption of the kynurenine pathway from particulate matter might promote diseases. Reducing exposure to the particulate matter is crucial for preventing adverse health effects. Full article

Inspired by the outstanding nature of flavonoid derivatives in the fields of chemistry and medicine, in this work we mainly focus on exploring the photo-induced properties of the novel Et₂N-substituted flavonoid (ENF) fluorophore theoretically. Considering the potential photo-induced properties in different solvents and the chalcogen atomic electronegativity-associated photoexcitation, by time-dependent density functional theory (TDDFT) methods we primarily explore the intramolecular hydrogen bonding interactions and photo-induced charge redistribution behaviors. Via comparing geometrical data and the infrared (IR) spectral shifts-associated hydroxy moiety of ENF, we confirm that the intramolecular hydrogen bond O-H···O should be enhanced with facilitating an excited-state intramolecular proton-transfer (ESIPT) reaction. Particularly, the charge reorganization around hydrogen bonding moieties further reveals the tendency of ESIPT behavior. Combined with the construction of the potential energy surface and the search for reaction transition states, we finally confirmed the solvent-polarity-regulated behaviors as well as the chalcogen elements’ electronegativity-dependent ESIPT mechanisms for the ENF fluorophore. We sincerely wish our work could accelerate the further development and applications of flavonoid derivatives. Full article

Supercapacitors have long suffered from low energy density. Here, we present a high-energy, high-safety, and temperature-adaptable aqueous proton battery utilizing two-dimensional Ti₃C₂T_x MXenes as anode materials. Additionally, our work aims to provide further insights into the energy storage mechanism of Ti₃C₂T_x in acid electrolytes. Our findings reveal that the ion transport mechanism of Ti₃C₂T_x remains consistent in both H₂SO₄ and H₃PO₄ electrolytes. The mode of charge transfer depends on its terminal groups. Specifically, the hydrogen bonding network formed by water molecules adsorbed by hydroxyl functional groups under van der Waals forces enables charge transfer in the form of naked H⁺ through the Grotthuss mechanism. In contrast, the hydrophobic channel formed by oxygen and halogen terminal groups facilitates rapid charge transfers in the form of hydronium ion via the vehicle mechanism, owing to negligible interfacial effect. Herein, we propose an aqueous proton battery based on porous hydroxy-poor Ti₃C₂T_x MXene anode and pre-protonated Cu^II[Fe^III(CN)₆]_2/3∙4H₂O (H-TBA) cathode in a 9.5 M H₃PO₄ solution. This proton battery operates through hydrated H⁺/H⁺ transfer, leading to good electrochemical performance, as evidenced by 26 Wh kg⁻¹ energy density and 162 kW kg⁻¹ power density at room temperature and an energy density of 17 Wh kg⁻¹ and a power density of 7.4 kW kg⁻¹ even at −60 °C. Full article