Recycling HPLC for the purification of oligostilbenes from Dipterocarpus semivestitus and Neobalanocarpus heimii (Dipterocarpaceae)

Medium pressure liquid chromatography and semipreparative high-performance liquid chromatography, followed by recycling high-performance liquid chromatography, were used for the isolation and purification of oligostilbenes from the acetone extracts of Dipterocarpus semivestitus and Neobalanocarpus heimii. Two stilbene dimers, ε-viniferin and cis-ε-viniferin, and a stilbene trimer, cis-miyabenol C were isolated from D. semivestitus. A trimer, ampelopsin C, and two tetramers, hemsleyanol D and isohopeaphenol, were isolated from N. heimii. The purities of the compounds were determined by an ultrahigh-performance liquid chromatography.     

The Anti-Adiposity Mechanisms of Ampelopsin and Vine Tea Extract in High Fat Diet and Alcohol-Induced Fatty Liver Mouse Models

Ampelopsis grossedentata (AG) is an ancient medicinal plant that is mainly distributed and used in southwest China. It exerts therapeutic effects, such as antioxidant, anti-diabetic, and anti-inflammatory activities, reductions in blood pressure and cholesterol and hepatoprotective effects. Researchers in China recently reported the anti-obesity effects of AG extract in diet-induced obese mice and rats. To verify these findings, we herein investigated the effects of AG extract and its principal compound, ampelopsin, in high-fat diet (HFD)- and alcohol diet-fed mice, olive oil-loaded mice, and differentiated 3T3-L1 cells. The results obtained showed that AG extract and ampelopsin significantly suppressed increases in the weights of body, livers and abdominal fat and also up-regulated the expression of carnitine palmitoyltransferase 1A in HFD-fed mice. In olive oil-loaded mice, AG extract and ampelopsin significantly attenuated increases in serum triglyceride (TG) levels. In differentiated 3T3-L1 cells, AG extract and ampelopsin promoted TG decomposition, which appeared to be attributed to the expression of hormone-sensitive lipase. In alcohol diet-fed mice, AG extract and ampelopsin reduced serum levels of ethanol, glutamic oxaloacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) and liver TG. An examination of metabolic enzyme expression patterns revealed that AG extract and ampelopsin mainly enhanced the expression of aldehyde dehydrogenase and suppressed that of cytochrome P450, family 2, subfamily e1. In conclusion, AG extract and ampelopsin suppressed diet-induced intestinal fat accumulation and reduced the risk of fatty liver associated with HFD and alcohol consumption.     

Separation of five oligostilbenes from Vitis amurensis by flow‐rate gradient high‐performance counter‐current chromatography

A rapid and efficient high‐performance counter‐current chromatography (HPCCC) method was developed to separate five oligostilbenes from the roots of Vitis amurensis. An n‐hexane/ethyl acetate/methanol/water system (4:8:4:10, v/v/v/v) was selected as an optimal two‐phase solvent system of which the upper phase was used as the stationary phase and the lower phase was used as the mobile one. Partition coefficient values for the target compounds under these optimized conditions were 0.28 ( 1 , ampleosin A), 7.12 ( 2 , (+)‐g‐viniferin), 2.26 ( 3 , vitisin A), 5.38 ( 4 , wilsonol C), and 11.23 ( 5 , vitisin B). Flow‐rate gradient HPCCC (4 mL/min in 0–70 min, 8 mL/min in 70–250 min) was applied to isolate the target compounds in as high purity as possible within the shortest possible run time. Under these conditions, ampelopsin A (12.1 mg), (+)‐g‐viniferin (10.4 mg), vitisin A (2.8 mg), wilsonol C (3.2 mg), and vitisin B (37 mg) were isolated with >95% purity from 150 mg of enriched oligostilbene extract. Although the K_D of the last eluted compound, vitisin B (K_D = 11.23), was relatively large, it was eluted in 115–145 min using the two‐phase solvent system. This study shows that HPCCC is an efficient tool for the isolation and purification of natural products.     

Lewis Superacidic Divalent Bis(m-terphenyl)element Cations [(2,6-Mes2C6H3)2E]+ of Group 13 Revisited and Extended (E=B,Al, Ga,In, Tl)

In a combined experimental and computational study, the molecular and electronic structures of the divalent bis(m-terphenyl)element cations [(2,6-Mes₂C₆H₃)₂E]⁺ of group 13 ( 1 , E=B; 2 , E=Al; 3 , E=Ga; 4 , E=In; 5 , E=Tl) were investigated. The preparation and characterization of 2 , 3 and 5 were previously reported by Wehmschulte's (Organometallics 2004 , 23, 1965–1967; J. Am. Chem. Soc. 2003 , 125, 1470–1471) and our groups (Organometallics 2009 , 28, 6893–6901). The indinium ion 4 was prepared and fully characterized for the first time. Attempts to prepare the borinium ion 1 by fluoride or hydride abstraction were unsuccessful. The electronic structures of 1 – 5 and the stabilization by the bulky m-terphenyl substituents were analyzed using quantum chemical calculations and compared to the divalent bis(m-terphenyl)pnictogenium ions [(2,6-Mes₂C₆H₃)₂E]⁺ of group 15 ( 6 , E=P; 7 , E=As; 8 , E=Sb; 9 , E=Bi) previously investigated by our group (Angew. Chem. Int. Ed. 2018 , 57, 10080–10084). The calculated fluoride ion affinities (FIA) of 1–9 are higher than that of SbF₅, which classifies them as Lewis superacids.     

Ultrasound Speeds and Molar Isentropic Compressions of Aqueous 2-(Ethylamino)ethanol Mixtures from 283.15 to 303.15 K

Ultrasound speeds in 31 aqueous binary mixtures of 2-(ethylamino)ethanol (EEA) were experimentally determined over the entire composition range at 283.15, 288.15 and 303.15 K. Isentropic compressibilities, κ _S , were calculated by combining the ultrasound speed with density data. Excess molar isentropic compressions, K_S,m^EK_{S,\mathrm{m}}^{\mathrm{E}}, referred to a thermodynamically-defined ideal liquid mixture, were estimated. Excess partial molar isentropic compressions, K_S,i^EK_{S,i}^{\mathrm{E}}, of both components and their respective limits at infinite dilution, K_S,i^E,￥K_{S,i}^{\mathrm{E,}\infty}, were analytically obtained using Redlich-Kister type equations. The temperature and composition dependences of K_S,i^EK_{S,i}^{\mathrm{E}} were analyzed, especially in the water and EEA rich regions. The present K_S,i^E,￥K_{S,i}^{\mathrm{E,}\infty} values are compared with those for water + 2-diethylaminoethanol (DEEA) and water + diethylamine (DEA) mixtures, as a function of temperature. Although the K_S,2^E,￥K_{S,2}^{\mathrm{E,}\infty} values for EEA and DEEA increase with temperature, the opposite trend is observed for DEA. Results for aqueous EEA and aqueous DEEA seem to support the idea that the driving force for hydrophobic hydration relies on solute-solvent hydrophilic interaction rather than on enhancing the water structure. On the other hand, different temperature dependent behavior is observed for the differential volumetric properties K_S,i^E,￥K_{S,i}^{\mathrm{E,}\infty} and limiting excess partial molar isobaric expansion, E_P,i^E,￥E_{P,i}^{\mathrm{E,}\infty}, which are attributed to the different sensitivity of these properties to hydration.     

First detection of Shiga toxin-producing Escherichia coli in shellfish and coastal environments of Morocco

Shiga toxin Escherichia coli (STEC), also called verotoxin-producing E. coli, is a major cause of food-borne illness, capable of causing hemorrhagic colitis and hemolytic–uremic syndrome (HUS). This study was carried out to evaluate the presence of (STEC) and E. coli O157:H7 in shellfish and Mediterranean coastal environments of Morocco. The contamination of shellfish and marine environment with Shiga toxin-producing E. coli (STEC) and E. coli O157:H7, was investigated during 2007 and 2008. A total of 619 samples were analyzed and 151 strains of E. coli were isolated. The presence of the stx1, stx2, and eae genes was tested in E. coli isolates strains using a triplex polymerase chain reaction. STEC was detected in three positives samples (1.9%), corresponding to the serotype O157:H7, the others Shiga toxin-producing E. coli non-O157 were also detected.     

Kinetics and thermal stability of two peroxidase isozymes from Eupatorium odoratum

The Eupatorium odoratum leaf peroxidase exists as at least seven distinct isozymes (three cationic, three anionic, and one neutral). These isozymes were identified and separated by preparative iso-electric focusing. Thermal stability, including the activation enthalpy (ΔH ^*), free energy of inactivation (ΔG ^*) and activation entropy (ΔS ^*), and kinetic studies of two isozymes, one having a pI of 5.0 (E5) and another one having a pI of 7.0 (E7) with mol mass of 43 and 50 kD, respectively, were studied in detail. Of the molecular weight of E5 and E7, 25 and 32% correspond to the carbohydrate content of the isozymes. Optimal pH was in the acidic range of 3.6–3.8 for E5 and 3.8 for E7 with the oxidation of ABTS. E7 and E5 showed activation energy for inactivation, 194.8 and 145.4 kJ/mol, respectively. Both the isozymes showed distinct substrate specificity. The catalytic specificity constant for E5 and E7 were 112×10⁵ and 124×10⁵/s·M, respectively, when 2,2′-azino-bis-(3-ethylbenz-thiazoline-6 sulfonic acid) was used as the substrate. Maximum affinity (i.e., lowest K _m value) to H₂O₂ was shown by E5 and E7 along with Pyrogallol and was 0.02 and 0.05/s·M, respectively.     

Chemical profile by LC–MS/MS,GC/MS and antioxidant activities of the essential oils and crude extracts of two Euphorbia species

In this study, it was aimed to investigate the chemical composition and antioxidant activities of two Euphorbia species. The major component of the fatty acid compositions obtained from the petroleum ether extracts was identified as palmitic acid for Euphorbia gaillardotii and Euphorbia macroclada. The main constituents of the essential oils were identified as arachidic acid for E. gaillardotii and tetratetracontane for E. macroclada. Among the 27 studied compounds, hesperidin, rutin, hyperoside and quinic, malic, gallic and tannic acids were found to be the most abundant compounds in the two Euphorbia species. The methanol extracts of E. gaillardotii and E. macroclada showed strong antioxidant activity in all tested methods. Particularly, IC₅₀ values of E. macroclada methanol extract that was the richest in terms of total phenolic-flavonoid contents were found to be lower than α-tocopherol and butylated hydroxytoluene in β-carotene bleaching, 2,2-diphenyl-1-picrylhydrazyl free and ABTS cation radical scavenging methods.     

Determination of <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript>-values for some elements in neutron capture gamma-ray for prompt gamma activation analysis

Exploration and modification of data for k ₀-PGAA (prompt γ-ray activation analysis) values used as standards for k ₀ standardization are needed. An integrated system has been installed and calibrated in Hot Laboratories Center for PGAA, using ²⁵²Cf isotopic neutron source with neutron flux of 6.16E8 n/cm² s. The prompt k ₀-factors of about 12 elements were determined versus the 1951.1 keV γ-ray of the ³⁵Cl, as well as analyzing crude oil and oil product samples. The concentrations of the elements in crude oil H, B, Mg, Al, Na, Si, P, S, Cl, V and Cd were 1.18E5, 0.084, 5.48E2, 8.45E2 4.88E2, 1.62E2, 3.72E2, 8.2, 144.3, 393 and 209.2 ppm while in oil product samples were 1.32E5, 5.87, 4.56E2, 4.22E2, 7.16E3, 699, 157, 8.74, 492.3, 61 and 198.2 ppm. Validation of the k ₀-PGAA was applied in analyzing standard IAEA reference material (soil-7) which give good agreement with the literature data. The ²⁵²Cf neutron beam in radiation position was characterized by the cadmium-ratio method, and found that the cadmium ratio (f), was 160.     

Chemical composition and antimicrobial activity of Erodium species: E. ciconium L., E. cicutarium L., and E. absinthoides Willd. (Geraniaceae)

The present study gives results of chemical composition analyses and antimicrobial activity testing of three Erodium species: E. ciconium L., E. cicutarium L., and E. absinthoides Willd. Essential oils were obtained by hydro-distillation from air-dried entire plants and analyzed by GC and GC-MS. A total of 209 different compounds were identified: 162 for E. cicutarium, 107 for E. ciconium, and 79 for E. absinthoides. Antimicrobial activity (broth microdilution method) of the oils was screened against a panel of Gram positive and Gram negative bacteria and a number of fungi. Moderate susceptibility of all tested strains was observed. Determined MIC values were 0.156–5 mg mL⁻¹ (bacterial strains) and 0.039–0.325 mg mL⁻¹ (fungal strains). Major component of the most active oil, palmitic acid, was also tested for activity together with stearic and myristic acids.     

Fabrication of an Electrochemical E. coli Biosensor in Biowells Using Bimetallic Nanoparticle‐Labelled Antibodies

An electrochemical biosensor was developed for the determination of Escherichia coli (E. coli) in water. For this purpose, silver‐gold core‐shell (Ag@Au) bioconjugates and anti‐E. coli modified PS‐microwells were designed in a sandwich‐type format in order to obtain higher sensitivity and selectivity. Ag@Au bimetallic nanoparticles were synthesized by co‐reduction method. The core‐shell formation was analyzed by using UV‐Vis spectroscopy and transmission electron microscopy. Biotin labeled anti‐E. coli antibodies were coupled with Ag@Au nanoparticles to form bioconjugates. The electrochemical immunosensor was prepared by immobilizing anti‐E. coli on polystyrene (PS)‐microwells via chemical bonding. These modified microwells were identified with X‐ray photoelectron spectroscopy and surface enhanced Raman spectroscopy. E. coli was sandwiched between Ag@Au bioconjugates and anti‐E. coli on PS‐microwells at different concentrations. The relationship between the E. coli concentration and stripping current of gold ions (Au³⁺) were investigated by square wave anodic stripping voltammetry at pencil graphite electrode. The proposed method can provide some advantages such as lower detection limit and shorter detection time. The electrochemical response for the immunosensor was linear with the concentration of the E. coli in the range of 10¹ and 10⁵ cfu/mL with a limit of detection 3 cfu/mL. The procedure maintains good sensitivity and repeatability and also offers utility in the fields of environmental monitoring and clinical diagnosis.     

Next-generation QTAIM for scoring molecular wires in E-fields for molecular electronic devices

The effect of a varying, directional E _x , E _y, and E _z electric field on the ethene molecule was investigated using next-generation quantum theory of atoms in molecules (QTAIM). Despite using low E -field strengths that are within the realm of experiment and do not measurably alter the molecular geometry, significant changes to the QTAIM properties were observed. Using conventional QTAIM, the shifting of the C─C and C─H bond critical points (BCPs) demonstrates polarization through an interchange in the size of the atoms involved in a bond, since a BCP is located on the boundary between a pair of bonded atoms. Next-generation QTAIM, however, demonstrates the polarization effect more directly with a change in morphology of the 3-D envelope around the BCP. Modest increases of ≈ 2% in the ellipticity ε of the BCP were uncovered when the C─C bond was aligned parallel or anti-parallel to the applied E _x -field. Significant asymmetries were found in the response of the next-generation QTAIM 3-D paths of the C─H bonds to the applied E -field. When the E -field coincided with the C─C bond, the BCP moved in response and was accompanied by the envelope constructed from 3-D next-generation paths. The response displayed a polarization effect that increased with increasing magnitude of the E _x -field parallel and anti-parallel to the C─C bond. Our analysis demonstrates that next-generation QTAIM is a useful tool for understanding the response of molecules to E -fields, for example, for the screening of molecular wires for the design of molecular electronic devices. © 2019 Wiley Periodicals, Inc.     

Syntheses of 2,6-O-alkyl celluloses: influence of methyl and ethyl groups regioselectively introduced at O-2 and O-6 positions on their solubility

2,6-Di-O-ethyl (2E6E) (1), 2-O-ethyl-6-O-methyl (2E6M) (2), and 6-O-ethyl-2-O-methyl (6E2M) (3) celluloses were synthesized via ring-opening polymerization of glucose orthopivalate derivatives. 2,6-Di-O-methyl cellulose (2M6M) was insoluble in any common solvents, though it was not expected. On the other hand, cellulose derivative 1 (2E6E) was soluble in chloroform. Introduced positions of alkyl groups on cellulose affected solubilities of cellulose derivatives. Their solubility in chloroform decreased in the order: polymer 1 (2E6E) > polymer 2 (2E6M) > polymer 3 (6E2M) ≫ 2M6M.     

A Facile Regio- and Stereocontrolled Synthesis of (E)-Vinylphosphonates VIA Cross Coupling of (E)-Vinyl Iodides with Dialkyl Phosphites

(E)-Vinylphosphonates were conveniently obtained under mild condition via the cross coupling of the corresponding (E)-vinyl iodides, which were obtained from the reaction of vinylzirconocenes with iodine, with dialkyl phosphites.     

Mass spectrometry of organic compounds in the group V elements—I: Straight chain aliphatic derivatives

Comparative investigations of the mass spectra of eEH₂, Me₂EH, Et₂EH(E = N, P); Me₃E, Et₃E(E = N, P, As, Sb, Bi). (n-Pr)₃E(E = Sb, Bi); (n-Bu)₃E(E = P, As); (n-C₅H₁₁)₃As and (n-C₆H₁₃)₃As as well as Et₂AsBr have been carried out. Deuteroanalogues, metastable transitions and low voltage spectra were used for elucidation of the fragmentation paths. The mass spectra of MeN(CH₂)₂ and CD₃N(CH₂)₂ were studied to analyse the structure of the fragments. The main degradation path of amines, i.e. α-cleavage, was shown to be untypical for P, As, Sb and Bi derivatives.     

Chemotyping of diverse Eucalyptus species grown in Egypt and antioxidant and antibacterial activities of its respective essential oils

The chemical composition of the essential oil from the leaves of Eucalyptus camaldulensis, Eucalyptus camaldulensis var. obtusa and Eucalyptus gomphocephala grown in northern Egypt was analysed by using GC-FID and GC–MS techniques. The antibacterial (agar disc diffusion and minimum inhibitory concentration methods) and antioxidant activities (2,2′-diphenypicrylhydrazyl) were examined. The main oils constituents were 1,8-cineole (21.75%), β-pinene (20.51%) and methyleugenol (6.10%) in E. camaldulensis; spathulenol (37.46%), p-cymene (17.20%) and crypton (8.88%) in E. gomphocephala; spathulenol (18.37%), p-cymene (19.38%) and crypton (16.91%) in E. camaldulensis var. obtusa. The essential oils from the leaves of Eucalyptus spp. exhibited considerable antibacterial activity against Gram-positive and Gram-negative bacteria. The values of total antioxidant activity were 70 ± 3.13%, 50 ± 3.34% and 84 ± 4.64% for E. camaldulensis, E. camaldulensis var. obtusa and E. gomphocephala, respectively. The highest antioxidant activity value of 84 ± 4.64% could be attributed to the high amount of spathulenol (37.46%).     

Synthesis of 32‐phenyl‐substituted methyl E/Z‐pyropheophorbide‐a's from methyl E/Z‐pyropehophorbide‐a 131‐ketoximes

Methyl E/Z‐pyropheophorbide‐a 13¹‐ketoximes 2a,b and their O‐acetyl derivatives 3a,b were oxidized with osmium(VIII) oxide to give aldehydes 4a,b and 5a,b , respectively. The Wittig reactions of the aldehyde chlorines 4a,b and 5a,b with benzyltriphenylphosphonium chloride were performed to form the corresponding methyl (3¹E/Z,13¹E/Z)‐3²‐phenylpyropheophorbide‐a 13¹‐ketoximes 6aa‐bb and their O‐acetyl derivatives 7aa‐bb ; hydrolysis of these ketoximes 6aa,ba and 6ab,bb in formic acid produced methyl (E/Z)‐3²‐phenylpyropheophorbide‐a's 8a,b .     

A strategy for the rapid discovery and validation of active diterpenoids as quality markers in different habitats of Langdu using ultrahigh-performance liquid chromatography–tandem mass spectrometry with multivariate statistical analysis

Langdu, known as a traditional Chinese medicine, was identified as the roots of species of Euphorbia ebracteolata Hayata and Euphorbia fischeriana Steud, displaying anti-tuberculosis activity. To clarify the potent quality markers of Langdu, this research first developed a fast and sensitive ultrahigh-performance liquid chromatography–tandem mass spectrometry method for the quantification of 13 diterpenoids in Langdu. The developed method was further applied in the analyses of 12 authentic E. ebracteolata and E. fischeriana samples collected in northern and southeastern China. Then, the anti-tuberculosis evaluation of 12 batches of Langdu samples was performed in vitro. Finally, partial least squares discrimination analysis was used in the discrimination of E. ebracteolata and E. fischeriana from different origins and processing methods. Jolkinolide A ( 1 ), jolkinolide E ( 3 ), yuexiandajisu D ( 6 ), and ebractenone A ( 11 ) were identified as key, potent diterpenoids for the quality control of E. ebracteolata Hayata and E. fischeriana Steud. The present study established a qualitative chemical analysis method for Langdu (E. ebracteolata and E. fischeriana) and suggested the key bioactive components that will improve qualitative control methodology for this important medicine.     

Chiral separation of novel diazenes on a polysaccharide‐based stationary phase in the reversed‐phase mode

Chiral high‐performance liquid chromatography separation of two recently synthesized liquid crystalline materials C1 and C2 was studied in the reversed‐phase mode. Both materials have an azo‐moiety and one chiral center in their molecular structures. They were available in racemic and pure S forms. For the enantiomeric separations, a Chiralpak AY‐RH stationary phase based on amylose tris(5‐chloro‐2‐methylphenylcarbamate) coated on 5 μm silica was used. The compounds were analyzed in both of their possible forms, the more thermodynamically stable E form and the labile Z form. The conditions and time scale of the UV‐induced E to Z transition were briefly evaluated. Under the optimized conditions, we were able to baseline separate S and R enantiomers of both of the studied materials not only in their E forms, but also in their Z forms. In comparison to the separation in the normal‐phase mode, which we have reported recently, the resolution in the reversed‐phase mode is significantly better. Interestingly, peak reversal was noticed for the S and R enantiomers when the separation was carried out with E versus Z forms of both compounds.     

GldA overexpressing-engineered E. coli as superior electrocatalyst for microbial fuel cells

Faster electron transfer between bacteria and electrodes in microbial fuel cells can significantly improve the power density of MFCs for practical applications. A recombinant Escherichia coli (E. coli) strain overexpressing glycerol dehydrogenase (GldA) was engineered as the MFC biocatalyst instead of the natural bacteria. Efficient mediators were produced in the fuel cell with this engineered E. coli resulting in lower polarization and much higher power density than with natural E. coli and E. coli with electro-evolved mediators. For the first time, we demonstrate that engineering E. coli by introduction of appropriate oxidoreductase via gene manipulation can greatly improve the rate of electron transfer. This work provides an efficient and economic approach to biologically engineering bacteria for improving MFC performance.