Position Of Hydroxyl Groups Research Articles

Significantly enhanced gas separation properties of membranes by debromination and thermal rearrangement simultaneously

One important challenge in advanced gas separation membranes is breaking the trade-off effect between gas permeability and selectivity. Here, we developed a method by combining the debromination and thermal rearrangement (TR) techniques together to significantly enhance the gas separation properties of the resulting membrane for the first time. First, we designed a co-polyimide (DBOH) containing both hydroxyl and bromine (50/50) groups in the ortho position of the imide group. After thermal treatment at 450 °C, the TR and debromination happened simultaneously as proved by TG-MS, FT-IR and XPS results, the resulting DBPO showed a larger d-spacing (7.03–9.71 Å), a 18-fold enhanced BET surface area, and 2-fold improved in ultra-microporosity (<7 Å) than its DBOH precursor. Hence, DBPO demonstrated not only an over 100 times improved CO2 permeability (7933 vs 76 Barrer) but also keep a high CO2/CH4 selectivity of 31, and the overall performance surpassed the latest 2019 trade-off curve. Besides, wonderful anti-plasticization and mixed-gas separation properties were also observed for DBPO, which showed a CO2 permeability of 3324 Barrer and CO2/CH4 selectivity of 14.7 even under the upstream CO2/CH4 mixed-gas pressure of 435 psi (1 psi = 6894.8 Pa), outperforming the latest 2018 CO2/CH4 mixed-gas upper limit. It showed 100 times improved CO2 permeability while maintain selectivity of DBPO is attributed to the significantly enhanced ultra-microporosity that increases the diffusion and solubility coefficient, whereas maintain their diffusion and solubility selectivity. Conclusively, the debromination coupled with TR provides a novel direction for designing advanced TR membranes.

Effect of RSN1 gene knockout on the adsorption of strontium ions by irradiated Saccharomyces cerevisiae

The irradiated Saccharomyces cerevisiae (Y-7) has good biosorption ability for strontium ions. To investigate the mechanism of strontium ion bioaccumulation in Y-7, we employed CRISPR/Cas9 gene editing technology to engineer Saccharomyces cerevisiae Y-7 and knock out the RSN1 gene, successfully constructing a RSN1 gene knockout strain (Y-7-rsn1Δ). When tested for strontium ion adsorption, the Y-7-rsn1Δ strain exhibited decreased capacity for adsorbing strontium ions and increased resistance to strontium ions. The results showed that RSN1 is involved in the transport of Sr2+, and observed significant decreases in intracellular Ca2+ of Y-7-rsn1Δ, indicating a strong correlation between bioaccumulation of Sr2+ and Ca2+. This demonstrated that the adsorption of strontium ions by Y-7 is regulated by the RSN1 gene. The knockout of the RSN1 gene resulted in the shift of the peak positions of carboxyl, amino, amide, hydroxyl, and phosphate groups on the cell surface.

Multiple Isomers of Photolumazine V Bind MR1 and Differentially Activate MAIT Cells.

In response to microbial infection, the nonclassical Ag-presenting molecule MHC class I-related protein 1 (MR1) presents secondary microbial metabolites to mucosal-associated invariant T (MAIT) cells. In this study, we further characterize the repertoire of ligands captured by MR1 produced in Hi5 (Trichoplusia ni) cells from Mycobacterium smegmatis via mass spectrometry. We describe the (to our knowledge) novel MR1 ligand photolumazine (PL)V, a hydroxyindolyl-ribityllumazine with four isomers differing in the positioning of a hydroxyl group. We show that all four isomers are produced by M. smegmatis in culture and that at least three can induce MR1 surface translocation. Furthermore, human MAIT cell clones expressing distinct TCR β-chains differentially responded to the PLV isomers, demonstrating that the subtle positioning of a single hydroxyl group modulates TCR recognition. This study emphasizes structural microheterogeneity within the MR1 Ag repertoire and the remarkable selectivity of MAIT cell TCRs.

Sucrose phosphorylase from Alteromonas mediterranea: Structural insight into the regioselective α-glucosylation of (+)-catechin

Sucrose phosphorylases, through transglycosylation reactions, are interesting enzymes that can transfer regioselectively glucose from sucrose, the donor substrate, onto acceptors like flavonoids to form glycoconjugates and hence modulate their solubility and bioactivity. Here, we report for the first time the structure of sucrose phosphorylase from the marine bacteria Alteromonas mediterranea (AmSP) and its enzymatic properties. Kinetics of sucrose hydrolysis and transglucosylation capacities on (+)-catechin were investigated. Wild-type enzyme (AmSP-WT) displayed high hydrolytic activity on sucrose and was devoid of transglucosylation activity on (+)-catechin. Two variants, AmSP-Q353F and AmSP-P140D catalysed the regiospecific transglucosylation of (+)-catechin: 89 % of a novel compound (+)-catechin-4′-O-α-d-glucopyranoside (CAT-4′) for AmSP-P140D and 92 % of (+)-catechin-3′-O-α-d-glucopyranoside (CAT-3′) for AmSP-Q353F. The compound CAT-4′ was fully characterized by NMR and mass spectrometry. An explanation for this difference in regiospecificity was provided at atomic level by molecular docking simulations: AmSP-P140D was found to preferentially bind (+)-catechin in a mode that favours glucosylation on its hydroxyl group in position 4′ while the binding mode in AmSP-Q353F favoured glucosylation on its hydroxyl group in position 3’.

Chemical Correlation of Cistendiol Obtained from Cativic Acid in Two Different Pathways

Objective This study aims to convert cativic acid, which was isolated from Ageratina jocotepecana, into cistendiol (5), an analog of cistenolic acid isolated from Cistus symphytifolius. The position of hydroxyl at C-7 in compound 5 could be achieved by applying the Schenck reaction with singlet oxygen (1O2) through photooxidation reaction of 6. Additionally, epoxidation reaction of 1, followed by further reduction and acid treatment, can serve as another pathway to obtain compound 5. Methods Cativic acid was isolated from Ageratina jocotepecana flowers, reduction methodology was realized with THF and LiAlH4, epoxidation reaction was carried out with mCPBA in CH2Cl2 and K2CO3, oxidation of alcohol with PCC in CH2Cl2 and MgSO4, photooxidation reaction was realized with blue and white light using singlet oxygen (1O2) and photosensitizers such as eosin, methylene blue and Ru(bpy)3(PF6)2 in acetonitrile. Geometry optimizations for transition states were performed using MMFF94 with Monte Carlo protocol, and GDFT was used B3LYP/DGDZVP level of theory with Gaussian 09. Results Cistendiol was synthesized by photooxidation reaction of 6 with Ru(bpy)3(PF6)2 and air such oxidant with a ratio of 8:1, while epoxidation of 1 further reduction and acid treatment afforded cistendiol with a ratio of 9:1, the ratio was determined by NMR, additionally the global minimum energy structures GDFT calculated values supports the results described by NMR ratio. The stereochemistry was also confirmed by NOESY experiment and the comparison is in agreement with literature data. Conclusion Herein, we described the conversion of cativic acid isolated from Ageratina jocotepecana employing a new photooxidation methodology and classic epoxidation techniques, to produce an analog of cistenolic acid isolated from Cistus symphytifolius. The results, which include Supplemental material, enable comparison of stereochemistry, specifically the 13 S for C-13 of Ageratina jocotepecana with other compounds such as cistenolic or salvic acid, which had been the subject of study by researchers.

FACILE PRODUCTION OF 4-HYDROXYBENZOIC ACID FROM OIL PALM EMPTY FRUIT BUNCH CELL WALLS BY ALKALI DEGRADATION AT ROOM TEMPERATURE

Oil palm empty fruit bunches are biorefinery waste produced from the oil palm factory. Palm lignin is partially ended with p-hydroxybenzoylated structure, which is a promising resource to produce 4-hydroxybenzoic acid. Herein, 4-hydroxybenzoic acid is produced by the degradation of oil palm empty fruit bunch cell walls with sodium hydroxide solution at room temperature without lignin isolation. The 4-hydroxybenzoic acid was obtained as the only main monomeric product from the process. The yield of 4-hydroxybenzoic acid can reach 7.87&amp;#37; based on the amount of oil palm empty fruit lignin. The sodium hydroxide concentration is the most important factor that affects the 4-hydroxybenzoic acid production yield and selectivity. The possible 4-hydroxybenzoic acid production routes were proposed. And the production route is considered to be formed mainly by the cleavage of C-O bonds at the &amp;gamma;-hydroxyl position of the syringyl unit in oil palm empty fruit bunch lignin.

Electrophysiology, molecular modelling, and functional analysis of the effects of dietary quercetin and flavonoid analogues on Kir6.1 channels in rat stomach fundus smooth muscle

Flavonoids, ubiquitously distributed in the plant world, are regularly ingested with diets rich in fruit, vegetables, wine, and tea. During digestion, they are partially absorbed in the stomach. The present work aimed to assess the in vitro effects of quercetin and ten structurally related flavonoids on the rat gastric fundus smooth muscle, focussing on ATP-dependent K+ (Kir6.1) channels, which play a central role in the regulation of resting membrane potential, membrane excitability and, consequently, of gastric motility. Whole-cell currents through Kir6.1 channels (IKir6.1) were recorded with the patch-clamp technique and the mechanical activity of gastric fundus smooth muscle strips was studied under isometric conditions. Galangin ≈ tamarixetin > quercetin > kaempferol > isorhamnetin ≈ luteolin ≈ fisetin > (±)-taxifolin inhibited pinacidil-evoked, glibenclamide-sensitive IKir6.1 in a concentration-dependent manner. Morin, rutin, and myricetin were ineffective. The steric hindrance of the molecule and the number and position of hydroxyl groups on the B ring played an important role in the activity of the molecule. Molecular docking simulations revealed a possible binding site for flavonoids in the C-terminal domain of the Kir6.1 channel subunit SUR2B, in a flexible loop formed by residues 251 to 254 of chains C and D. Galangin and tamarixetin, but not rutin relaxed both high K+- and carbachol-induced contraction of fundus strips in a concentration-dependent manner. Furthermore, both flavonoids shifted to the right the concentration-relaxation curves to either pinacidil or L-cysteine constructed in strips pre-contracted by high K+, rutin being ineffective. In conclusion, IKir6.1 inhibition exerted by dietary flavonoids might counterbalance their myorelaxant activity, affect gastric accommodation or, at least, some stages of digestion.

Highly oxidized flavones in Artemisia species – structure revisions and improved UHPLC-MSn analysis

In course of our studies of the aerial parts of Artemisia abrotanum the major methoxyflavonol could be isolated. However, by NMR structural analysis it became obvious that the substitution pattern in ring B differs from reports for casticin (2). The position of methoxyl and hydroxyl groups are interchanged, i.e., the major flavone is actually chrysosplenetin (1). Three structures in A. abrotanum and A. frigida had to be revised. Use of pyridine-d5 instead of DMSO‑d6 made the resolution of the B-ring 1H and 13C NMR signals possible and enabled correct structural assignment by 2D NMR experiments.Results from NMR structure elucidation for A. abrotanum were confirmed by LC-PDA-ESI-MSn analysis when a PFP (pentafluorophenyl) stationary phase with an optimized gradient elution was applied for separation of 1 and 2 instead of a corresponding C-18 phase. Electrospray mass spectrometry (positive and negative mode) with subsequent fragmentation (ESI-MSn) revealed distinctive mass spectral features of both compounds, especially at MS4 level. Several Artemisia extracts including A. annua were analysed on the PFP phase for the presence of 1 and 2.

Effect of hydroxyl position in reagent molecule on coal dust dedusting

Using the high-speed motion acquisition system, we studied the adhesion ability and wetting ability of coal dust under the effect of four octanol solutions. The adhesion ability followed the order: 2-Octanol > 4-Octanol > 1-Octanol > 3-Octanol. The wrap angle of coal dust on the octanol surface exhibited an increasing trend with the rise in coal proportion of dust. The observed behavior was substantiated by the interaction force, ascertained through molecular dynamic simulations. The interaction force between coal dust and 3-Octanol was the smallest leading to the weakest adhesion ability by the 3-Octanol solution. The contact angle of octanol solution droplet at the coal dust surface under the same octanol concentration was investigated to follow the order: 2-Octanol > 4-Octanol > 1-Octanol > 3-Octanol. The wetting velocity decreased as the coal proportion of dust increased. The wetting ability followed the order: 2-Octanol < 4-Octanol < 1-Octanol < 3-Octanol. The surface energy of dust increased as the coal proportion decreased. The dedusting efficient under the effect of octanols depended on the difference in surface energy between the coal dust and the octanol solution. The greater the Δγ (difference between the surface energy of the dust and solution), the weaker the adhesion ability, and the stronger the wetting ability. The findings of our study can offer valuable insights for the development of dedusting reagent design.

Effect of hydroxyl position on antioxidant ability of hydroxycoumarin derivatives: A theoretical investigation

Effect of the OH group position on the antioxidant ability of hydroxycoumarin derivatives (HOC) was investigated by quantum chemical computation. Frontier molecular orbitals, molecular electrostatic potential, and thermodynamic parameters were analyzed in detail. The results indicate that 3-HOC, 6-HOC, and 7-HOC exhibit as the best reactants with free radicals through analysis of global reactivity descriptor values, meanwhile H (in OH groups) of 4-HOC, 5-HOC, 6-HOC, and 7-HOC molecules are the most preferable sites for nucleophilic attacks. Besides, thermodynamic and kinetic studies reveal hydrogen atomic transfer is the primary mechanism when hydroxycoumarin derivatives react with HOO• free radical in the gas phase and pentyl ethanoate. Hydrogen atomic transfer products account for over 97 % of the total products of hydrogen atomic transfer and radical adduct formation mechanisms. According to the study, 6-HOC is the most effective scavenger of free radicals when compared to other derivatives, with a rate constant of 1.38 × 104 M−1s−1 in the gas phase and 6.5 × 103 M−1s−1 in pentyl ethanoate. The interaction of O20∙∙∙H21 in the transition state of 6-HOC is crucial in stabilizing its structure. This finding suggests that 6-HOC can be a potential candidate for developing antioxidants for various applications in the medical and industrial fields. The results of this study provide valuable insights into the mechanisms by which antioxidants can scavenge free radicals and protect against oxidative stress.

Structure-Chiral Selectivity Relationships of Various Mandelic Acid Derivatives on Octakis 2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl-gamma-cyclodextrin Containing Gas Chromatographic Stationary.

Frequently, a good chiral separation is the result of long trial and error processes. The three-point interaction mechanisms require the fair geometrical fitting and functional group compatibility of the interacting groups. Structure-chiral selectivity correlations are guidelines that can be established via trough systematic studies using model compounds. The enantiorecognition of the test compounds was studied on an octakis 2,3-Di-O-acetyl-6-O-tert-butyldimethylsilyl-gamma-cyclodextrin (TBDMSDAGCD) chiral selector. In our work, mandelic acid and its variously substituted compounds were used as model compounds to establish adaptable rules for other enantiomeric pairs. The mandelic acid and its modified compounds were altered at both their carboxyl and hydroxyl positions to test the key interaction forces of the chiral recognition processes. Ring- and alkyl-substituted mandelic acid derivatives were also used in our experiments. The chiral selectivity values of 20 test compounds were measured and extrapolated to 100 °C. The hydrogen donor abilities of test compounds improved their chiral selectivities. The inclusion phenomenon also played a role in chiral recognition processes in several cases. Enantiomer elution reversals were observed for different derivatives of hydroxyl groups, providing evidence for the multimodal character of the selector. The results of our research can serve as guidelines to achieve appropriate chiral separation for other enantiomeric pairs.

Mur ligase F as a new target for the flavonoids quercitrin, myricetin, and (-)-epicatechin.

MurC, D, E, and F are ATP-dependent ligases involved in the stepwise assembly of the tetrapeptide stem of forming peptidoglycan. As highly conserved targets found exclusively in bacterial cells, they are of significant interest for antibacterial drug discovery. In this study, we employed a computer-aided molecular design approach to identify potential inhibitors of MurF. A biochemical inhibition assay was conducted, screening twenty-four flavonoids and related compounds against MurC-F, resulting in the identification of quercitrin, myricetin, and (-)-epicatechin as MurF inhibitors with IC50 values of 143 µM, 139 µM, and 92 µM, respectively. Notably, (-)-epicatechin demonstrated mixed type inhibition with ATP and uncompetitive inhibition with D-Ala-D-Ala dipeptide and UM3DAP substrates. Furthermore, in silico analysis using Sitemap and subsequent docking analysis using Glide revealed two plausible binding sites for (-)-epicatechin. The study also investigated the crucial structural features required for activity, with a particular focus on the substitution pattern and hydroxyl group positions, which were found to be important for the activity. The study highlights the significance of computational approaches in targeting essential enzymes involved in bacterial peptidoglycan synthesis.

Self-assembly and interaction mechanisms of edible dock protein and flavonoids regulated by the phenolic hydroxyl position.

In this study, chrysin (Chr), baicalein (Bai), apigenin (Api) and galangin (Gal) were selected as the representative flavonoids with different position of phenolic hydroxyl groups, and edible dock protein (EDP) was used as a material to construct delivery system. Subsequently, the molecular interactions and functional properties of flavonoids-loaded EDP nanomicelles were investigated. Results exhibited that hydrogen bond, hydrophobic interaction and van der Waals force were the main driving forces for self-assembly of flavonoids and EDP molecules. Meanwhile, this self-assembly remarkably enhance the storage and digestion stability of flavonoid compounds. Among four flavonoids, the order of loading ability was: Api>Gal>Bai>Chr. Herein, Api had a largest loading capacity (6.74%) because of its active phenolic hydroxyl group in ring B. These results suggested that the position of phenolic hydroxyl groups in flavonoids is a key factor to regulate its self-assembly with protein molecules.

Copper catalyzed Shono-type oxidation of proline residues in peptide.

Since the initial report in 1975, the Shono oxidation has become a powerful tool to functionalize the α position of amines, including proline derivatives, by electrochemical oxidation. However, the application of electrochemical Shono oxidations is restricted to the preparation of simple building blocks and homogeneous Shono-type oxidation of proline derivatives remains challenging. The late-stage functionalization at proline residues embedded within peptides is highly important as substitutions about the proline ring are known to affect biological and pharmacological activities. Here, we show that homogenous copper-catalyzed oxidation conditions complement the Shono oxidation and this general protocol can be applied to a series of formal C-C coupling reactions with a variety of nucleophiles using a one-pot procedure. This protocol shows good tolerance toward 19 proteinogenic amino acids and was used to functionalize several representative bioactive peptides, including captopril, enalapril, Smac, and endomorphin-2. Last, peptide cyclization can also be achieved by using an appropriately positioned side-chain hydroxyl moiety.

Adsorption of Sc on the Surface of Kaolinite (001): A Density Functional Theory Study.

The adsorption behavior of Sc on the surface of kaolinite (001) was investigated using the density functional theory via the generalized gradient approximation plane-wave pseudopotential method. The highest coordination numbers of hydrated Sc3+, ScOH2+, and ScOH2 + species are eight, six, and five, respectively. The adsorption model was based on ScOH2H2O5+, which has the most stable ionic configuration in the liquid phase. According to the adsorption energy and bonding mechanism, the adsorption of Sc ionic species can be categorized into outer layer and inner layer adsorptions. We found that the hydrated Sc ions were mainly adsorbed on the outer layer of the kaolinite (001)Al-OH and (00-1)Si-O surfaces through hydrogen bonding while also being adsorbed on the inner layer of the deprotonated kaolinite (001)Al-OH surface through coordination bonding. The inner layer adsorption has three adsorption configurations, with the lying hydroxyl group (Ol) position having the lowest adsorption energy (-653.32 KJ/mol). The adsorption energy for the inner layer is lower compared to the outer layer, while the extent of deprotonation is limited. This is because the deprotonation of the inner adsorption layer is energetically unfavorable. We speculate that Sc ions species predominantly adsorb onto the surface of kaolinite (001) in an outer layer configuration.

Structural and Multi-functional properties of isoelectronic guanyl hydrazinium picolinic derivatives exhibit centric and non-centric space group

The equimolar reaction mixture of isoelectronic picolinic acid N-oxide (PAHNO) and/or 3-hydroxy picolinic acid (3-HPAH) with guanyl hydrazine bicarbonate (AgunH.HCO3) in aqueous medium at room temperature produce 1:1 salt. Irrespective of the molar ratios (1; 1, 1:2 & 2:1) and reaction conditions maintained, invariably gives the same product in the form of polycrystalline nature except 1:1 ratio which yields a single crystal. The isoelectronic salts were characterized by spectroscopic, PXRD, thermal study and single crystal X-ray diffraction techniques. In general, most of the salts were crystallized in a centric space group rather than a non-centric, the prevailing factors are nature of the organic species and reaction conditions like pH, pKa, solvent effects, temperature and molar ratio etc,. Surprisingly, in the present case, the isoelectric salt of [AgunH]+[PANO]- crystalized in centric (P21/n), where in case of [AgunH]+[3-HPA]- crystalized in non-centric (Pca21) space group even though in the same reaction conditions. This may be due to the presence of the 3rd position of hydroxyl group and non-covalent interactions in [AgunH]+[3-HPA]- that facilitate non-centric space group. Both salts are stabilized by the variety of hydrogen bond features leading to intra- and intermolecular N-H⋯O, N-H⋯N, and C-H⋯N hydrogen bonds and π-π stacking interactions along with homo- and hetero ring motifs [two R22 (8), R11 (6), and two R22 (9)]. These interactions render them an appropriate acid-base ion pair for the formation of sturdy hydrogen-bonded supramolecular synthons. Thermal studies on these salts reveal that the thermal degradation occurs via melting followed by complete loss of organic species. The solid-state emission spectra of free acids and its salts were recorded and compared. The materials exhibit a prominent luminescent character towards red shift than the starting compounds. Further, these materials show enhanced secondary antioxidant and antimicrobial activities, this is due to the crucial role of hydrazine species in guanyl hydrazinium cation.

Bioassay-guided isolation of BACE1 inhibitors from Crataegus pinnatifida

BackgroundCrataegus pinnatifida, functional food has been used in traditional Chinese medicine due to its significant pharmacological effects on various metabolic disorders, neurodegenerative diseases, as well as anti-cancer and anti-viral properties. Despite numerous studies reporting its anti-Alzheimer's disease (AD) activity, there is currently no research on the potential of its extract or constituents to inhibit β-site amyloid precursor protein cleaving enzyme 1 (BACE1). MethodsThe study aimed to evaluate the inhibitory effects of the methanolic extract of C. pinnatifida and its solvent-soluble fractions on cholinesterase and β-site amyloid precursor protein cleaving enzyme 1 (BACE1). Following a bioassay-guided isolation, we identified several compounds, including two triterpenoids [corosolic acid (1), euscaphic acid (2)], β-sitosterol glucoside (3), three flavonoids [astragalin (4), hyperoside (5), isovitexin (6)], and four phenolic acid derivatives [gentisic acid (7), protocatechuic acid (8), p-hydroxybenzoic acid (9), p-coumaric acid (10)] from EtOAc fraction. Additionally, two triterpenoids (3-epicorosolic acid (11) and ursolic acid (12)) and β-sitosterol (13) were isolated from the CH2Cl2 fraction, while isoorientin (14) and hymenoside X (15) were isolated from n-BuOH fraction. Notably, compounds 2, 7, 10, and 14 were reported for the first time from the fruit of C. pinnatifida. ResultsWe observed that 3-epicorosolic acid (11) exhibited promising inhibitory activity against BACE1 with IC50 values of 40.12 ± 1.72 µM. Hyperoside (5) showed moderate activity with IC50 values of 98.50 ± 4.20 µM, while corosolic acid (1) and astragalin (4) displayed mild BACE1 inhibitory activity, with IC50 values of 179.55 ± 1.57 and 192.30 ± 5.14 µM, respectively. We also investigated the structure activity relationship of ursane-type triterpenoids based on in vitro and in silico results, which revealed that the hydroxyl groups position of the triterpenes have a significant impact on their potency. Our findings suggest that α‑hydroxyl group at the C-2 and C-3 positions and the absence of α‑hydroxyl group at the C-19 position are essential for BACE1 inhibitory activity. ConclusionsThis study highlights the significance of the configuration and position of hydroxyl groups and their impact on BACE1 inhibitory activity. The findings of this study could be leveraged to develop novel therapeutic approaches for Alzheimer's disease.

Naturally Occurring Chalcones with Aggregation-Induced Emission Enhancement Characteristics.

In this paper, the natural chalcones: 2'-hydroxy-4,4',6'-trimethoxychalcone (HCH), cardamonin (CA), xanthohumol (XN), isobavachalcone (IBC) and licochalcone A (LIC) are studied using spectroscopic techniques such as UV-vis, fluorescence spectroscopy, scanning electron microscopy (SEM) and single-crystal X-ray diffraction (XRD). For the first time, the spectroscopic and structural features of naturally occurring chalcones with varying numbers and positions of hydroxyl groups in rings A and B were investigated to prove the presence of the aggregation-induced emission enhancement (AIEE) effect. The fluorescence studies were carried out in the aggregate form in a solution and in a solid state. As to the results of spectroscopic analyses conducted in the solvent media, the selected mixtures (CH3OH:H2O and CH3OH:ethylene glycol), as well as the fluorescence quantum yield (ϕF) and SEM, confirmed that two of the tested chalcones (CA and HCH) exhibited effective AIEE behaviour. On the other hand, LIC showed a large fluorescence quantum yield and Stokes shift in the polar solvents and in the solid state. Moreover, all studied compounds were tested for their promising antioxidant activities via the utilisation of 1,1- diphenyl-2-picrylhydrazyl as a free-radical scavenging reagent as well as potential anti-neurodegenerative agents via their ability to act as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors. Finally, the results demonstrated that licochalcone A, with the most desirable emission properties, showed the most effective antioxidant (DPPH IC50 29%) and neuroprotective properties (AChE IC50 23.41 ± 0.02 μM, BuChE IC50 42.28 ± 0.06 μM). The substitution pattern and the biological assay findings establish some relation between photophysical properties and biological activity that might apply in designing AIEE molecules with the specified characteristics for biological application.

Adsorption and Desorption of Bile Salts at Air–Water and Oil–Water Interfaces

Bile Salts (BS) adsorb onto emulsified oil droplets to promote lipolysis and then desorb, solubilizing lipolytic products, a process which plays a crucial role in lipid digestion. Hence, investigating the mechanism of adsorption and desorption of BS onto the oil–water interface is of major importance to understand and control BS functionality. This can have implications in the rational design of products with tailored digestibility. This study shows the adsorption and desorption curves of BS at air–water and oil–water interfaces obtained by pendant drop tensiometry. Three BS have been chosen with different conjugation and hydroxyl groups: Sodium Taurocholate (NaTC), Glycodeoxycholate (NaGDC) and Sodium Glycochenodeoxycholate (NaGCDC). Experimental results show important differences between the type of BS and the nature of the interface (air/oil–water). At the air–water interface, Glycine conjugates (NaGDC and NaGCDC) are more surface active than Taurine (NaTC), and they also display lower surface tension of saturated films. The position of hydroxyl groups in Glycine conjugates, possibly favors a more vertical orientation of BS at the surface and an improved lateral packing. These differences diminish at the oil–water interface owing to hydrophobic interactions of BS with the oil, preventing intermolecular associations. Desorption studies reveal the presence of irreversibly adsorbed layers at the oil–water interface in all cases, while at the air–water interface, the reversibility of adsorption depends strongly on the type of BS. Finally, dilatational rheology shows that the dilatational response of BS is again influenced by hydrophobic interactions of BS with the oil; thus, adsorbed films of different BS at the oil–water interface are very similar, while larger differences arise between BS adsorbed at the air–water interface. Results presented here highlight new features of the characteristics of adsorption layers of BS on the oil–water interface, which are more relevant to lipid digestion than characteristics of BS adsorbed at air–water interfaces.

Robust unsymmetric pincer-type Ru(II) catalyst containing proton-responsive hydroxypyridyl fragment for β-alkylation of secondary alcohols with primary alcohols

A highly efficient metal-ligand bifunctional pincer-type Ru(II) catalyst (LOH-Ru-Cl) containing proton-responsive 2-hydroxypyridyl group has been designed and synthesized. The as-synthesized Ru(II) catalyst was definitely characterized by single-crystal X-ray diffraction. The developed Ru(II) catalyst exhibited excellent performance for the β-alkylation of secondary alcohols with primary alcohols. The optimized experiments have demonstrated that the existence of hydroxyl (-OH) group, as well as its position contained in pyridine ligand are crucial for the β-alkylation reaction. As far as we know, this is the first investigation towards the effect of position of hydroxyl (-OH) group contained in unsymmetric pincer-type catalyst on the performance of β-alkylation. The developed LOH-Ru-Cl catalyst may provide an enlightening role for synthesis of Ru(II) catalyst contained various position of hydroxyl (-OH) groups for industrial β-alkylation reactions.