Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 4.266
Filtrar
Más filtros

Tipo del documento
Intervalo de año de publicación
1.
J Nat Med ; 78(3): 608-617, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38587582

RESUMEN

The relative configuration of the epoxide functionality in pinofuranoxin A (1), α-alkylidene-ß-hydroxy-γ-methyl-γ-butyrolactone with trans-epoxy side chain isolated by Evidente et al. in 2021, was revised by DFT-based spectral reinvestigations and stereo-controlled synthesis. The present investigation demonstrates the difficulty of the configurational elucidation of the stereogenic centers on the conformationally flexible acyclic side-chains. Sharpless's enantioselective epoxidations and dihydroxylations were quite effective in the reinvestigations of the configurations. As our syntheses made all diastereomers available, these would be quite effective in the next structure-biological activity relationship studies.


Asunto(s)
4-Butirolactona , Estereoisomerismo , Estructura Molecular , 4-Butirolactona/química , 4-Butirolactona/análogos & derivados , 4-Butirolactona/síntesis química , Relación Estructura-Actividad , Conformación Molecular
2.
J Chromatogr A ; 1722: 464911, 2024 May 10.
Artículo en Inglés | MEDLINE | ID: mdl-38626541

RESUMEN

In this study, we have synthesised a chiral l-hyp-Ni/Fe@SiO2 composite as a chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) for the first time. This was achieved by coating two-dimensional (2D) chiral metal-organic framework nanosheets (MONs) l-hyp-Ni/Fe onto the surface of activated SiO2 microspheres using the "wrapped in net" method. The separation efficiency of the l-hyp-Ni/Fe chromatographic column was systematically evaluated in normal-phase HPLC (NP-HPLC) and reversed-phase HPLC (RP-HPLC) configurations, employing various racemates as analytes. The findings revealed that 16 chiral compounds were separated using NP-HPLC, and five were separated using RP-HPLC, encompassing alcohols, amines, ketones, esters, alkanes, ethers, amino acids and sulfoxides. Notably, the resolution (Rs) of nine chiral compounds exceeded 1.5, indicating baseline separation. Furthermore, the resolution performance of the l-hyp-Ni/Fe@SiO2-packed column was compared with that of Chiralpak AD-H. It was observed that certain enantiomers, which either could not be resolved or were inadequately separated on the Chiralpak AD-H column, attained separation on the 2D chiral MONs column. These findings suggest a complementary relationship between the two columns in racemate separation, with their combined application facilitating the resolution of a broader spectrum of chiral compounds. In addition, baseline separation was achieved for five positional isomers on the l-hyp-Ni/Fe@SiO2-packed column. The effects of the analyte mass and column temperature on the resolution were also examined. Moreover, during HPLC analysis, the l-hyp-Ni/Fe columns demonstrated commendable repeatability, stability and reproducibility in enantiomer separation. This research not only advances the utilisation of 2D chiral MONs as CSPs but also expands their applications in the separation sciences.


Asunto(s)
Estructuras Metalorgánicas , Dióxido de Silicio , Cromatografía Líquida de Alta Presión/métodos , Dióxido de Silicio/química , Estructuras Metalorgánicas/química , Estereoisomerismo , Nanoestructuras/química , Hierro/química , Níquel/química
3.
J Chromatogr A ; 1722: 464857, 2024 May 10.
Artículo en Inglés | MEDLINE | ID: mdl-38569445

RESUMEN

Epimer separation is crucial in the field of analytical chemistry, separation science, and the pharmaceutical industry. No reported methods could separate simultaneously epimers or even isomers and remove other unwanted, co-existing, interfering substances from complex systems like herbal extracts. Herein, we prepared a heptapeptide-modified stationary phase for the separation of 1R,2S-(-)-ephedrine [(-)-Ephe] and 1S,2S-(+)-pseudoephedrine [(+)-Pse] epimers from Ephedra sinica Stapf extract and blood samples. The heptapeptide stationary phase was comprehensively characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The separation efficiency of the heptapeptide column was compared with an affinity column packed with full-length ß2-AR functionalized silica gel (ß2-AR column). The binding affinity of the heptapeptide with (+)-Pse was 3-fold greater than that with (-)-Ephe. Their binding mechanisms were extensively characterized by chromatographic analysis, ultraviolet spectra, circular dichroism analysis, isothermal titration calorimetry, and molecule docking. An enhanced hydrogen bonding was clearly observed in the heptapeptide-(+)-Pse complex. Such results demonstrated that the heptapeptide can recognize (+)-Pse and (-)-Ephe epimers in a complex system. This work, we believe, was the first report to simultaneously separate epimers and remove non-specific interfering substances from complex samples. The method was potentially applicable to more challenging sample separation, such as chiral separation from complex systems.


Asunto(s)
Efedrina , Seudoefedrina , Receptores Adrenérgicos beta 2 , Efedrina/química , Seudoefedrina/química , Receptores Adrenérgicos beta 2/química , Receptores Adrenérgicos beta 2/metabolismo , Simulación del Acoplamiento Molecular , Ephedra sinica/química , Cromatografía Líquida de Alta Presión/métodos , Extractos Vegetales/química , Humanos , Estereoisomerismo , Oligopéptidos/química , Oligopéptidos/aislamiento & purificación
4.
Angew Chem Int Ed Engl ; 63(19): e202402050, 2024 May 06.
Artículo en Inglés | MEDLINE | ID: mdl-38488804

RESUMEN

Germacranolides, secondary metabolites produced by plants, have garnered academic and industrial interest due to their diverse and complex topology as well as a wide array of pharmacological activities. Molephantin, a highly oxygenated germacranolide isolated from medicinal plants, Elephantopus mollis and Elephantopus tomentosus, has exhibited antitumor, inflammatory, and leishmanicidal activities. Its chemical structure is based on a highly strained ten-membered macrocyclic backbone with an (E,Z)-dienone moiety, which is fused with an α-methylene-γ-butyrolactone and adorned with four successive stereogenic centers. Herein, we report the first synthesis of molephantin in 12 steps starting from readily available building blocks. The synthesis features the highly diastereoselective intermolecular Barbier allylation of the ß,γ-unsaturated aldehyde with optically active 3-bromomethyl-5H-furan-2-one intermediate and ensuing Nozaki-Hiyama-Kishi (NHK) macrocyclization for the construction of the highly oxygenated ten-membered macrocyclic framework. This synthetic route enabled access to another germacranolide congener, tomenphantopin F. Furthermore, cycloisomerization of molephantin into 2-deethoxy-2ß-hydroxyphantomolin could be facilitated by irradiation with ultraviolet A light (λmax=370 nm), which opened a versatile and concise access to the related furanogermacranolides such as EM-2, phantomolin, 2-O-demethyltomenphantopin C, and tomenphantopin C.


Asunto(s)
Oxígeno , Oxígeno/química , Asteraceae/química , Estereoisomerismo , Sesquiterpenos de Germacrano/química , Sesquiterpenos de Germacrano/síntesis química , Furanos/química , Furanos/síntesis química , Estructura Molecular
5.
Int J Biol Macromol ; 262(Pt 1): 130013, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38340930

RESUMEN

A natural polysaccharide-based vehicle is facilely prepared for enantioselective loading of S-naproxen (S-NPX) and its programmed release. Cyclodextrin metal-organic frameworks (CD-MOF) are synthesized through the coordination of K+ with γ-cyclodextrin (γ-CD). Compared with R-NPX, the CD-MOF preferably combines with S-NPX, which can be confirmed by the thermodynamic calculations. The S-NPX loaded CD-MOF (CD-MOF-S-NPX) is grafted with disulfide bond (-S-S-) to improve its hydrophobicity, and the loaded S-NPX is further encapsulated in the chiral cavity of γ-CD by carboxymethyl potato starch (CPS) hydrogels. The intermolecular hydrogen bonding of the CPS hydrogels is prone to be destroyed in mildly basic media (∼pH 8.0), resulting in the swelling of the hydrogels; the -S-S- linkage in the vehicle can be cleaved in the presence of glutathione (GSH), leading to the collapse of the CD-MOF. Therefore, the programmed release of S-NPX can be achieved. Also in this work, the release kinetics is investigated, and the results indicate that the release of S-NPX is controlled by the Higuchi model.


Asunto(s)
Ciclodextrinas , Estructuras Metalorgánicas , Solanum tuberosum , Ciclodextrinas/química , Naproxeno/química , Estructuras Metalorgánicas/química , Hidrogeles , Estereoisomerismo
6.
J Chromatogr A ; 1718: 464710, 2024 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-38330727

RESUMEN

The separation of vitamin A acetate isomers is essential for quality assurance of e.g. nutrition supplements, cosmetics, and pharmaceutical ingredients. High performance liquid chromatography (HPLC) is currently the most suitable analytical method for tackling this challenging separation task. However, the existing methods based on normal phase chromatography (NPC) are poorly reproducible due to the typical disadvantages of NPC, such as long equilibration times and fluctuation in retention factors. A new reversed phase method developed in our labs allows the separation of the isomers applying a chiral stationary phase (CSP). This phase consists of an immobilized polysaccharide which can be used in every chromatographic mode. However, they are not typically used in reversed phase mode. Through the screening of various stationary phases with different polysaccharide based chiral selectors, the choice of the ideal stationary phase could be confirmed, allowing to draw conclusions about the retention mechanism. The CSP Chiralpak IG-3 was found to be the most suitable among the examined. Regarding the separation mechanism, the spatial helical structure of the polysaccharide derivatives was confirmed to be of particular significance. In addition to the stationary phase, the mobile phase was tested for optimization regarding composition, gradient parameters as well as temperature using chromatographic method optimization software for the sake of method robustness.


Asunto(s)
Amilosa , Diterpenos , Polisacáridos , Ésteres de Retinilo , Amilosa/química , Estereoisomerismo , Polisacáridos/química , Cromatografía Líquida de Alta Presión/métodos
7.
J Sep Sci ; 47(3): e2300921, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38356221

RESUMEN

Glutamine is the most abundant free proteinogenic α-amino acid. It is naturally produced in the organism and acts as a precursor for the synthesis of different biologically important molecules (such as proteins or nucleotides). However, under stressful conditions, the organism is unable to produce it in enough amounts to function properly. Thus, glutamine (Gln)-based supplements have become increasingly popular over the last decade. Since legal regulations establish that amino acid-based dietary supplements must contain only the L-enantiomer and not the racemate, adequate chiral methodologies are required to achieve their quality control. In this work, an analytical methodology based on the use of micellar electrokinetic chromatography is proposed for the rapid enantiomeric determination of DL-Gln in dietary supplements. Using (+)-1-(9-fluorenyl)-ethyl chloroformate as a derivatizing agent and ammonium perfluorooctanoate as separation medium, the Gln diastereoisomers formed under optimal conditions were separated in 8 min with a resolution of 2.8. The analytical characteristics of the method were evaluated in terms of linearity, precision, accuracy, and limits of detection/quantitation, and they were found appropriate for the analysis of L-Gln-based dietary supplements.


Asunto(s)
Cromatografía Capilar Electrocinética Micelar , Glutamina , Cromatografía/métodos , Aminoácidos/química , Suplementos Dietéticos/análisis , Estereoisomerismo , Cromatografía Capilar Electrocinética Micelar/métodos
8.
Chin J Nat Med ; 21(12): 886-901, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-38143103

RESUMEN

In carbohydrate chemistry, the stereoselective synthesis of 1,2-cis-glycosides remains a formidable challenge. This complexity is comparable to the synthesis of 1,2-cis-ß-D-mannosides, primarily due to the adverse anomeric and Δ-2 effects. Over the past decades, to attain ß-stereoselectivity in D-rhamnosylation, researchers have devised numerous direct and indirect methodologies, including the hydrogen-bond-mediated aglycone delivery (HAD) method, the synthesis of ß-D-mannoside paired with C6 deoxygenation, and the combined approach of 1,2-trans-glycosylation and C2 epimerization. This review elaborates on the advancements in ß-D-rhamnosylation and its implications for the total synthesis of tiacumicin B and other physiologically relevant glycans.


Asunto(s)
Glicósidos , Manósidos , Glicosilación , Estereoisomerismo
9.
Molecules ; 28(17)2023 Aug 24.
Artículo en Inglés | MEDLINE | ID: mdl-37687059

RESUMEN

Quality control of essential oils is fundamental for verifying their authenticity and conformity with quality standards, ensuring their safety and regulatory compliance, and monitoring their consistency. Companies that produce or market essential oils routinely evaluate the quality and authenticity of their products. However, they also must deal with increasing attention to environmental sustainability as well as practical considerations such as productivity, cost, and simplicity of methods. In this study, enantioselective gas chromatography (GC) was adopted to evaluate the quality of sweet and bitter orange essential oils, used as a case study. The analytical conditions were optimized and translated to fast GC to evaluate the impact of this approach on the environmental footprint of the analyses. The greenness of fast GC, compared with conventional GC, was quantitatively evaluated using a dedicated metric tool (AGREE), and important improvements have been calculated. The developed methods were applied to a set of commercial essential oils, and the data about the enantiomeric composition and relative percentage abundance were elaborated through multivariate statistics (principal component analysis). The results showed that fast chiral gas chromatography enables the classification of citrus essential oil samples and can be considered an environmentally friendly and sustainable approach for evaluating their quality.


Asunto(s)
Citrus , Aceites Volátiles , Cromatografía de Gases y Espectrometría de Masas , Estereoisomerismo , Control de Calidad , Cromatografía de Gases , Extractos Vegetales
10.
Chem Biodivers ; 20(9): e202300941, 2023 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-37548481

RESUMEN

Four pairs of aryldihydronaphthalene-type lignanamide enantiomers were isolated from Solanum lyratum (Solanaceae). The enantiomeric separation was accomplished by chiral-phase HPLC, and five undescribed compounds were elucidated. Analysis by various spectroscopy and ECD calculations, the structures of undescribed compounds were illuminated. The neuroprotective effects of all compounds were evaluated using H2 O2 -induced human neuroblastoma SH-SY5Y cells and AchE inhibition activity. Among them, compound 4 a exhibited remarkable neuroprotective effects at high concentrations of 25 and 50 µmol/L comparable to Trolox. Compound 1 a showed the highest AchE inhibition with the IC50 value of 3.06±2.40 µmol/L. Molecular docking of the three active compounds was performed and the linkage between the compounds and the active site of AchE was elucidated.


Asunto(s)
Neuroblastoma , Fármacos Neuroprotectores , Solanum , Humanos , Solanum/química , Fármacos Neuroprotectores/química , Simulación del Acoplamiento Molecular , Estereoisomerismo , Estructura Molecular
11.
J Sep Sci ; 46(20): e2300318, 2023 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-37590330

RESUMEN

Enantiomeric separation of furanocoumarins and dihydroflavones compounds were systematically studied in the normal-phase mode using four different polysaccharide-type chiral stationary phases, namely, Chiralpak IA, Chiralpak IC, Chiralpak IG, and Chiralpak IK-3 by high-performance liquid chromatography. The effect of alcohol modifiers and alcohol content on enantiomeric separation was evaluated for the separation of furanocoumarins and dihydroflavones. All the eight compounds have achieved baseline separation with the resolutions ranging between 1.52 and 23.11. For a better insight into the enantiorecognition mechanisms, thermodynamic analysis was carried out. The mechanisms of chiral recognition have been discussed. Among four chiral columns, Chiralpak IG exhibited the most universal and the best enantioseparation ability toward furanocoumarins and dihydroflavones when used n-hexane-isopropanol and n-hexane-ethanol as mobile phase, respectively. The steric hindrance, hydrogen bonding, and π-π interaction played major roles in chiral recognition on Chiralpak IG. By comparing four chiral columns, this work systematically analyzed the separation methods of furanocoumarins and dihydroflavones for the first time and reported some active chiral ingredients of traditional Chinese medicine that have never been separated, which provided a further insight into the enantioseparation of furanocoumarins and dihydroflavones on chiral stationary phases.


Asunto(s)
Furocumarinas , Polisacáridos/química , Hexanos , Cromatografía Líquida de Alta Presión/métodos , Etanol , Estereoisomerismo
12.
J Org Chem ; 88(13): 8413-8430, 2023 Jul 07.
Artículo en Inglés | MEDLINE | ID: mdl-37322607

RESUMEN

A copper and chiral nitroxide co-catalyzed aerobic enantioselective oxidation process has been developed that allows access to axially chiral molecules. Two complementary atroposelective approaches, oxidative kinetic resolution (OKR) and desymmetrization, were studied using ambient air as the stoichiometric terminal oxidant. OKR of rac-N-arylpyrrole alcohols and rac-biaryl alcohols affords the optically pure compounds with er up to 3.5:96.5 and 5.5:94.5, respectively. Desymmetrization of prochiral diols provides axially chiral biaryl compounds with er up to 99:1.


Asunto(s)
Alcoholes , Estereoisomerismo , Catálisis , Oxidación-Reducción , Cinética
13.
Molecules ; 28(11)2023 May 24.
Artículo en Inglés | MEDLINE | ID: mdl-37298774

RESUMEN

The aim of the research described in this publication is two-fold. The first is a detailed description of the synthesis of a series of compounds containing a stereogenic heteroatom, namely the optically active P-stereogenic derivatives of tert-butylarylphoshinic acids bearing sulfur or selenium. The second is a detailed discussion dedicated to the determination of their structures by an X-ray analysis. Such a determination is needed when considering optically active hetero-oxophosphoric acids as new chiral solvating agents, precursors of new chiral ionic liquids, or ligands in complexes serving as novel organometallic catalysts.


Asunto(s)
Compuestos Organometálicos , Selenio , Compuestos Organometálicos/química , Cristalografía por Rayos X , Estereoisomerismo
14.
Int J Mol Sci ; 24(10)2023 May 11.
Artículo en Inglés | MEDLINE | ID: mdl-37239965

RESUMEN

Rare ginsenosides are the major components of red ginseng. However, there has been little research into the relationship between the structure of ginsenosides and their anti-inflammatory activity. In this work, BV-2 cells induced by lipopolysaccharide (LPS) or nigericin, the anti-inflammatory activity of eight rare ginsenosides, and the target proteins expression of AD were compared. In addition, the Morris water maze test, HE staining, thioflavins staining, and urine metabonomics were used to evaluate the effect of Rh4 on AD mice. Our results showed that their configuration influences the anti-inflammatory activity of ginsenosides. Ginsenosides Rk1, Rg5, Rk3, and Rh4 have significant anti-inflammatory activity compared to ginsenosides S-Rh1, R-Rh1, S-Rg3, and R-Rg3. Ginsenosides S-Rh1 and S-Rg3 have more pronounced anti-inflammatory activity than ginsenosides R-Rh1 and R-Rg3, respectively. Furthermore, the two pairs of stereoisomeric ginsenosides can significantly reduce the level of NLRP3, caspase-1, and ASC in BV-2 cells. Interestingly, Rh4 can improve the learning ability of AD mice, improve cognitive impairment, reduce hippocampal neuronal apoptosis and Aß deposition, and regulate AD-related pathways such as the tricarboxylic acid cycle and the sphingolipid metabolism. Our findings conclude that rare ginsenosides with a double bond have more anti-inflammatory activity than those without, and 20(S)-ginsenosides have more excellent anti-inflammatory activity than 20(R)-ginsenosides.


Asunto(s)
Enfermedad de Alzheimer , Ginsenósidos , Panax , Ratones , Animales , Ginsenósidos/farmacología , Ginsenósidos/uso terapéutico , Ginsenósidos/química , Enfermedad de Alzheimer/tratamiento farmacológico , Estereoisomerismo , Panax/química
15.
Chirality ; 35(9): 540-548, 2023 09.
Artículo en Inglés | MEDLINE | ID: mdl-37142400

RESUMEN

Cannabicitran is a cannabinoid found in levels up to ~10% in commercial "purified" cannabidiol (CBD) extracts. The structure of this natural product was first reported more than 50 years ago. However, few studies have investigated cannabicitran or its origin despite the rapidly increasing interest in the use of cannabinoids for the treatment of a wide range of physiological conditions. Following on a recent detailed NMR and computational characterization of cannabicitran, our group initiated ECD and TDDFT studies aimed at unequivocally determining the absolute configuration of cannabicitran present in Cannabis sativa extracts. To our surprise, we discovered the natural product was racemic, raising questions around its presumed enzymatic origin. Herein, we report the isolation and absolute configuration of (-)-cannabicitran and (+)-cannabicitran. Several possible scenarios for production of the racemate in the plant and/or during extract processing are discussed.


Asunto(s)
Cannabidiol , Cannabinoides , Cannabis , Estereoisomerismo , Cannabidiol/química , Cannabis/química , Extractos Vegetales/química
16.
Food Res Int ; 169: 112891, 2023 07.
Artículo en Inglés | MEDLINE | ID: mdl-37254338

RESUMEN

Chiral volatiles play important roles in the formation of aroma quality of foods. To date, enantiomeric characteristics of chiral volatiles in Wuyi rock tea (WRT) and their aroma contributions are still unclear. In this study, an efficient enantioselective comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (Es-GC × GC-TOFMS) approach to separate and precisely quantitate 24 pairs of chiral volatiles in WRTs was established, and the enantiomeric distribution and aroma contribution of chiral volatiles among WRTs from four representative cultivars were investigated. Enantiomeric ratio (ER) of R-α-ionone (80%) in Dahongpao (DHP), ER of S-α-terpineol (57%) in Jinfo (JF), ERs of R-γ-heptanolactone (69%), S-γ-nonanolactone (55%), (2R, 5S)-theaspirane B (91%), concentration of S-(E)-nerolidol (313.37 ng/mL) in Rougui (RG) and concentration of R-α-ionone (33.01 ng/mL) in Shuixian (SX) were unique from other types of WRTs, which were considered as the potential chemical markers to distinguish WRT cultivars. The OAV assessment determined 7 volatile enantiomers as the aroma-active compounds, especially R-α-ionone and R-δ-octanolactone in SX, as well as S-(E)-nerolidol and (1R, 2R)-methyl jasmonate in RG contribute much to aroma formation of the corresponding WRTs. The above results provide scientific references for discrimination of tea cultivars and directed improvement of the aroma quality of WRT.


Asunto(s)
, Compuestos Orgánicos Volátiles , Té/química , Estereoisomerismo , Compuestos Orgánicos Volátiles/análisis
17.
Zhongguo Zhong Yao Za Zhi ; 48(5): 1273-1279, 2023 Mar.
Artículo en Chino | MEDLINE | ID: mdl-37005811

RESUMEN

To elucidate the chemical material basis of Rhododendron nivale, this study comprehensively used various chromatographic techniques to isolate and obtain five new meroterpenoid enantiomers(1a/1b-5a/5b) from the ethyl acetate extract of R. nivale. A variety of spectral analytical methods, such as high-resolution mass spectrometry(HRMS), nuclear magnetic resonance spectroscopy(NMR), and infrared(IR) spectrum, were used to evaluate the structure, combined with the measurement and calculation of electronic circular dichroism(ECD). The new compounds 1a/1b-4a/4b were named as(±)-nivalones A-B(1a/1b-2a/2b) and(±)-nivalnoids C-D(3a/3b-4a/4b), along with one known enantiomer(±)-anthoponoid G(5a/5b). Human neuroblastoma cells(SH-SY5Y cells) induced by hydrogen peroxide(H_2O_2) were used as oxidative stress models to evaluate the protective activity of the isolated compounds against oxidative damage to nerve cells. It was found that compounds 2a and 3a had a certain protective effect on nerve cells against H_2O_2-induced oxidative damage at concentrations of 50 µmol·L~(-1), which increased the cell survival rate from 44.02%±2.30% to 67.82%±1.12% and 62.20%±1.87%, respectively. Other compounds did not show a significant ability to protect cells from oxidative damage. These findings enrich the chemical constituents of R. nivale and provide valuable information for identifying the structure of its meroterpenoids.


Asunto(s)
Neuroblastoma , Rhododendron , Humanos , Rhododendron/química , Estrés Oxidativo , Espectroscopía de Resonancia Magnética , Estereoisomerismo , Estructura Molecular
18.
J Chromatogr A ; 1692: 463845, 2023 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-36803769

RESUMEN

In this work, the vacuum-assisted thermal bonding method was proposed for the covalent coupling of ß-cyclodextrin (ß-CD) (CD-CSP), hexamethylene diisocyanate cross-linked ß-CD (HDI-CSP) and 3, 5-dimethylphenyl isocyanate modified ß-CD (DMPI-CSP) onto the isocyanate silane modified silica gel. Under vacuum conditions, the side reaction due to the water residue from the organic solvent, air, reaction vessels and silica gel could be avoided, and the optimal temperature and time of vacuum-assisted thermal bonding method were determined as 160°C and 3 h. These three CSPs were characterized by FT-IR, TGA, elemental analysis and the nitrogen adsorption-desorption isotherms. The surface coverage of CD-CSP and HDI-CSP on silica gel was determined as ∼0.2 µmol m-2, respectively. The chromatographic performances of these three CSPs were systematically evaluated by separating 7 flavanones, 9 triazoles and 6 chiral alcohols enantiomers under the reversed-phase condition. It was found that the chiral resolution ability of CD-CSP, HDI-CSP and DMPI-CSP was complementary to each other. Among them, CD-CSP could separate all 7 flavanones enantiomers with the resolution of 1.09-2.48. HDI-CSP had a good separation performance for triazoles enantiomers with one chiral center. DMPI-CSP showed excellent separation performance for chiral alcohol enantiomers, among which the resolution of trans-1, 3-diphenyl-2-propen-1-ol reached 12.01. Generally, the vacuum-assisted thermal bonding had been demonstrated as a direct and efficient method for the preparation of chiral stationary phases of ß-CD and its derivatives.


Asunto(s)
Flavanonas , beta-Ciclodextrinas , Cromatografía Líquida de Alta Presión/métodos , Gel de Sílice , Espectroscopía Infrarroja por Transformada de Fourier , beta-Ciclodextrinas/química , Estereoisomerismo , Etanol , Triazoles , Dióxido de Silicio/química
19.
Environ Res ; 224: 115514, 2023 05 01.
Artículo en Inglés | MEDLINE | ID: mdl-36801231

RESUMEN

Penthiopyrad is a widely used chiral fungicide for controlling rust and Rhizoctonia diseases. Development of optically pure monomers is an important strategy to realize amount reduction and increment effects of penthiopyrad, wherein, fertilizers as the co-exiting nutrient supplement may alter the enantioselective residues of penthiopyrad in soil. In our study, influences of urea, phosphate, potash, NPK compound, organic granular, vermicompost and soya bean cake fertilizers on enantioselective persistence of penthiopyrad were fully evaluated. This study demonstrated that R-(-)-penthiopyrad dissipated faster than S-(+)-penthiopyrad during 120 days. High pH, available nitrogen, invertase activities and reduced available phosphorus, dehydrogenase, urease, catalase activities were situated to benefit removing the concentrations of penthiopyrad and weakening enantioselectivity in soil. With respect to the impact of different fertilizers on soil ecological indicators, vermicompost contributed to enhanced pH. Urea and compound fertilizer played an absolute advantage in promoting available nitrogen. All fertilizers didn't go against available phosphorus. Dehydrogenase responded negatively to phosphate, potash and organic fertilizers. Urea increased invertase, besides, it and compound fertilizer both diminished urease activity. The catalase activity was not activated by organic fertilizer. Based on all the findings, soil application of urea and phosphate fertilizers was recommended and considered as a better option to exhibit high efficiency for the dissipation of penthiopyrad. The combined environmental safety estimation can effectively guide the treatment of fertilization soils in line with the nutrition requirements and pollution regulation from penthiopyrad.


Asunto(s)
Fertilizantes , Suelo , Suelo/química , Ureasa , Estereoisomerismo , Catalasa , beta-Fructofuranosidasa , Fósforo , Fosfatos , Antioxidantes , Nitrógeno/análisis , Urea/química , Fertilización , Agricultura
20.
J Asian Nat Prod Res ; 25(10): 919-940, 2023 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-36748290

RESUMEN

Neolignans and lignans with diverse new chemical structures, including eleven pairs of separated chiral enantiomers [(+)-/(-)-1-(+)-/(-)-5, (+)-/(-)-8, (+)-/(-)-10, and (+)-/(-)-12-(+)-/(-)-15], two achiral compounds (6 and 9), and an unseparated racemate [(±)-11], together with a new natural product (7) and 21 known derivatives, were isolated from an aqueous extract of the Angelica sinensis root head (guitou). Among the chiral isolates, (+)-/(-)-13 and (+)-/(-)-15 were scalemic pairs with enantiomeric ratios of around 3:1 and 1.5:1, respectively, while others were enantiomeric equivalent pairs. This indicates that the diverse neolignans in A. sinensis are biosynthesized via different pathways with varying degrees of stereo-controlled manners.


Asunto(s)
Angelica sinensis , Medicamentos Herbarios Chinos , Lignanos , Lignanos/química , Estereoisomerismo
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA