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1.
Anal Chem ; 94(49): 16997-17002, 2022 12 13.
Artículo en Inglés | MEDLINE | ID: mdl-36453024

RESUMEN

The resolving power of multiple dimensional liquid chromatography (mD-LC) is multiplicative as it adds dimensions. However, the issue in creating a preparative mD-LC system is that the higher the dimensionality, the more complicated the system configuration. Thus, we presented a new configuration of preparative mD-LC using one set of LC modules and trapping array-based multiple heart-cut interfaces. A preparative two-dimensional liquid chromatography (2D-LC) separation of herbal medicine formulation produced 40 compounds with a purity of >90%. During the separation process, the interface stores the fractions and allocates positions for the fractions from a different dimension; LC draws the fraction from the interface, makes nD separation, and sends isolated fractions to the interface. By repeating this process, we achieved variable dimensionality of LC separations. We also presented a preparative 3D-LC separation of herbal medicines to validate the principle of "less configuration and more dimensionality". Thus, we can explore the higher dimensional preparative separations. The developed preparative mD-LC displayed exceptional power in the isolation of various compounds and has great potential in the application of natural products.


Asunto(s)
Productos Biológicos , Cromatografía Líquida de Alta Presión/métodos , Cromatografía Liquida/métodos
2.
Anal Chem ; 94(38): 13000-13009, 2022 09 27.
Artículo en Inglés | MEDLINE | ID: mdl-36102213

RESUMEN

In this work, the first version of "Glycomapping" software is developed for the analysis of the most common low-molecular-weight heparin (LMWH), enoxaparin. Using ultrahigh-performance liquid chromatography-mass spectrometry, size exclusion chromatography is applied, and a virtual database of glycans in enoxaparin is established for the initial searching. With "Glycomapping", a complex chromatogram can be fitted, significantly improving resolution and confirming an accurate distribution range for each size of glycan within enoxaparin. In addition, randomly matched MS data can be corrected, with the constraint of the corresponding chromatographic retention time range, to remove most false positive data. The analytical stability of "Glycomapping" software was confirmed. Enoxaparin, prepared by different manufacturers and from different animal sources, was analyzed using "Glycomapping." Compared to raw data, data processed with "Glycomapping" are more robust and accurate. Another two LMWHs, nadroparin and dalteparin could also be analyzed with this software. This work lays a solid foundation for the automated analysis of heterogeneous mixtures of natural glycans, such as LMWHs and other complex oligosaccharides and polysaccharides.


Asunto(s)
Enoxaparina , Heparina de Bajo-Peso-Molecular , Animales , Anticoagulantes , Cromatografía Liquida , Dalteparina , Enoxaparina/química , Heparina/química , Heparina de Bajo-Peso-Molecular/análisis , Nadroparina/química , Programas Informáticos
3.
Anal Bioanal Chem ; 407(1): 231-40, 2015 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-25171829

RESUMEN

The analysis of chemical constituents in Chinese herbal medicines (CHMs) is a challenge because of numerous compounds with various polarities and functional groups. Liquid chromatography coupled with quadrupole time-of-flight (QTOF) mass spectrometry (LC/MS) is of particular interest in the analysis of herbal components. One of the main attributes of QTOF that makes it an attractive analytical technique is its accurate mass measurement for both precursor and product ions. For the separation of CHMs, comprehensive two-dimensional chromatography (LCxLC) provides much higher resolving power than traditional one-dimensional separation. Therefore, a LCxLC-QTOF-MS system was developed and applied to the analysis of flavonoids and iridoid glycosides in aqueous extracts of Hedyotis diffusa (Rubiaceae). Shift gradient was applied in the two-dimensional separation in the LCxLC system to increase the orthogonality and effective peak distribution area of the analysis. Tentative identification of compounds was done by accurate mass interpretation and validation by UV spectrum. A clear classification of flavonol glycosides (FGs), acylated FGs, and iridoid glycosides (IGs) was shown in different regions of the LCxLC contour plot. In total, five FGs, four acylated FGs, and three IGs were tentatively identified. In addition, several novel flavonoids were found, which demonstrates that LCxLC-QTOF-MS detection also has great potential in herbal medicine analysis.


Asunto(s)
Cromatografía Líquida de Alta Presión/métodos , Medicamentos Herbarios Chinos/química , Flavonoides/química , Hedyotis/química , Glicósidos Iridoides/química , Espectrometría de Masas/métodos , Cromatografía Líquida de Alta Presión/instrumentación , Espectrometría de Masas/instrumentación , Estructura Molecular
4.
Anal Bioanal Chem ; 407(1): 153-67, 2015 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-25311191

RESUMEN

Online comprehensive two-dimensional liquid chromatography (online LCxLC) presents high peak capacity compared with one-dimensional liquid chromatography, and reasonable operation time compared with an offline or stop-flow mode. Among various combinations, coupling of two reversed-phase (RPxRP) columns generates a high peak capacity product rate. Its wide applicability made RPxRP a promising technique in separation of complex samples. This review discusses the practical considerations in development and application of an RPxRP system, including systematic investigation of column stationary phase chemistry, column combinations, mobile phase system, interface, gradient types, and achieving fast analysis in LCxLC. In addition, many efforts are given to methods that increase the fraction coverage because this is the main obstacle caused by the correlated separation mechanism in RPxRP.

5.
J Nanosci Nanotechnol ; 15(1): 600-5, 2015 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-26328411

RESUMEN

The biodegradable microcapsules based on chitosan for a controlled delivery of clove oil were prepared by the single coagulation process. The effect of chitosan concentration, core to shell ratio, types of emulsifier, flocculating agent and hardening agent on the microcapsule diameter and the particle size distribution of microcapsule were investigated. The optimized conditions for the preparation of microcapsules with well-defined structure and narrow dispersibility were under that (1) the concentration of chitosan was 1.0 wt%, (2) clove oil to chitosan ratio was 75:25, (3) OP-10 and 10 wt% sodium sulfate were used as emulsifier and flocculating agent respectively, and (4) the concentration hardening agent glyoxal was 1 wt% based on the weight of chitosan. The uniform spherical structures with smooth surfaces with a particle size distribution of 1-15 µm were evidenced by SEM images of microcapsules. Core-shell, hetero-structures were confirmed by optical micrograph. The chemical component of the microcapsules was determined by FTIR. Thermal analysis showed the microcapsules were thermally stable below 150 degrees C. It was found that the pH value and temperature play important roles on the release rate of clove oil from the microcapsules. The release volume of clove oil from microcapsules at pH = 7, and pH = 10 were smaller than that at pH = 2. And the release volume of Clove oil from microcapsules at 60 degrees C was smaller than that at 20 degrees C and 40 degrees C, which showed a sustained and prolonged release.


Asunto(s)
Cápsulas/química , Aceite de Clavo/química , Quitosano/química , Aceite de Clavo/farmacocinética , Preparaciones de Acción Retardada/química , Preparaciones de Acción Retardada/farmacocinética , Floculación , Concentración de Iones de Hidrógeno , Tamaño de la Partícula , Espectroscopía Infrarroja por Transformada de Fourier
6.
J Chromatogr A ; 1719: 464730, 2024 Mar 29.
Artículo en Inglés | MEDLINE | ID: mdl-38367394

RESUMEN

Polysaccharides have unique physio-chemical properties and various biological functions and have rapidly expanded interest over the last two decades. The purification of polysaccharides and their degraded oligosaccharides is challenging because carbohydrates have no chromophore and need a proper detector to monitor the chromatographic elution process. This study proposed an active derivatization detection (ADD) method based on active splitting from post-column flow, a microchannel reactor for efficient derivatization of polysaccharide reducing sugars with p-hydroxybenzoic acid hydrazide, and in-line detection by the UV detector of liquid chromatography system. The method and device were validated by the use of 11 monosaccharides, sulfated oligosaccharides (from degraded carrageenan), and polysaccharides (from Zizania latifolia). It has shown much better performance than the traditional phenol-sulfuric acid method (gold standard). Moreover, the ADD module presumes an add-in to the original preparative LC system, independent of the scale of the purification process and type of system. The developed method is versatile for chromatographic separation of carbohydrates and lays the foundation for their subsequent studies.


Asunto(s)
Carbohidratos , Oligosacáridos , Cromatografía Líquida de Alta Presión/métodos , Carbohidratos/análisis , Cromatografía Liquida , Oligosacáridos/química , Polisacáridos/química
7.
Int J Biol Macromol ; 254(Pt 1): 127679, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-37890741

RESUMEN

The swollen culm (also known as Jiaobai) of Zizania latifolia is formed by the smut Ustilago esculenta invades the Z. latifolia. The new tissue formed due to the symbiotic relationship has entices the attention of researchers to study its polysaccharide structure along with biological evaluation. Five fractions of polysaccharides were obtained owing to hot water extraction, alcoholic precipitation, and chromatographic purification. Bioactivity assays showed that ZLPs have good antioxidant, hypoglycemic activities and protective activity against oxidative damage. The ZLP-1 and ZLP-2 were determined to be neutral polysaccharides with high purity, exhibiting propitious bioactivity, consequently they were subjected to indispensable structural characterization. These results showed that ZLP-1 has molecular weight (Mw) of 103 kDa and glucose (Glc) (76.68 %) as the primary monosaccharide; the ZLP-2 has Mw of 122 kDa and galactose (Gal) (41.04 %) and arabinose (Ara) (27.12 %). Structural elucidation by methylation and nuclear magnetic resonance (NMR) analysis suggested ZLP-1 is a glucan, with →3)-ß-Glcp-(1→3)-ß-Glcp-(1→4)-ß-Glcp-(1→4)-ß-Glcp-(1→3,6)-ß-Galp-(1→3)-ß-Glcp-(1→ as the mainchain and the terminal Araf and Glcp; the ZLP-2 is a Galactoxylan, with →3,4)-ß-xylp-(1→3)-ß-Galp-(1→3,6)-ß-Galp-(1→3,6)-ß-Galp-(1→ as the mainchain and the terminal Araf and Glcp. The structural arrangements provide a chemical basis for understanding the nutritional and pharmacological activities of polysaccharides from Zizania latifolia.


Asunto(s)
Glucanos , Polisacáridos , Polisacáridos/química , Monosacáridos/análisis , Antioxidantes/química , Galactosa
8.
Int J Biol Macromol ; 261(Pt 2): 129709, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38286380

RESUMEN

The dried root of Pueraria mirifica (P. mirifica) is an edible foodstuff widely used in Asian countries. P. mirifica is known for its high starch content. The isolation of polysaccharides from high-starch plant parts is challenging due to the interference of starch. Therefore, this study aimed to develop a technique for isolating and investigating the structure and activity of non-glucan polysaccharides from P. mirifica (PMP). An effective starch removal process was developed using α-amylase hydrolysis and thorough membrane dialysis. Four non-glucan polysaccharides were isolated, and PMP-2 was subjected to structural elucidation. The results indicated that PMP-2 has a molecular weight of 124.4 kDa and that arabinose and galactose are the main components, accounting for 27.8 % and 58.5 %, respectively. Methylation and NMR analysis suggested that PMP-2 is an Arabinogalactan composed of 1,6-linked Galp and 1,4-linked Galp as the main chain, with arabinan and rhamnose as side chains. Furthermore, PMP-C and PMP-2 exhibited concentration-dependent antioxidant activities against DPPH, ABTS, and hydroxyl radicals and certain immunomodulatory activities related to the release of NO, TNF-α and IL-6. These findings suggest that PMP-2 has potential therapeutically active ingredient in functional foods. The developed method successfully removed starch and isolated non-glucan polysaccharides from the high-starch content plant P. mirifica and can be applied to other high-starch plants.


Asunto(s)
Pueraria , Pueraria/química , Almidón , Diálisis Renal , Extractos Vegetales , Antioxidantes , Polisacáridos/farmacología
9.
Int J Biol Macromol ; 258(Pt 1): 128878, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38141709

RESUMEN

Snail mucus had medical applications for wound healing as early as ancient Greece and the late Han Dynasty (China). A literature search found 165 modern research papers discussing the extraction methods, chemical compositions, pharmacological activities, and applications of snail mucus. Thus, this review summarized the research progress on the extraction, structure, pharmacological activities, and applications of polysaccharides and proteins isolated from snail mucus. The extraction methods of snail mucus include natural secretion and stimulation with blunt force, spray, electricity, un-shelling, ultrasonic-assisted, and ozone-assisted. As a natural product, snail mucus mainly comprises two polysaccharides (glycosaminoglycan, dextran), seven glycoproteins (mucin, lectin), various antibacterial peptides, allantoin, glycolic acid, etc. It has pharmacological activities that encourage cell migration and proliferation, and promote angiogenesis and have antibacterial, anti-oxidative and anticancer properties. The mechanism of snail mucus' chemicals performing antibacterial and wound-healing was proposed. Snail mucus is a promising bioactive product with multiple medical applications and has great potential in the pharmaceutical and healthcare industries. Therefore, this review provides a valuable reference for researching and developing snail mucus.


Asunto(s)
Antibacterianos , Polisacáridos , Polisacáridos/química , Antibacterianos/farmacología , Moco/química , Lectinas/metabolismo , Glicosaminoglicanos/metabolismo
10.
Int J Biol Macromol ; 266(Pt 1): 130725, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38490394

RESUMEN

Carrageenan (CGN) is a typical sulfated polysaccharide widely applied in the food and pharmaceutical industries. Its in vivo behavior plays vital roles in understanding structural and biological functional relationships. The lack of UV chromophores in highly sulfated polysaccharides presents a challenge for their in vivo behavior studies. Therefore, this study aimed to develop a fast and effective quantitative fluorescence method for investigating the pharmacokinetics and tissue distribution of CGN. Fluorescence isothiocyanate labeling of CGN (FCGN) and microplate reader-based measurements were developed and validated to study its pharmacokinetics. These results showed that the FCGN concentration peaked at 3 h, the mean residence time was 36.6 h, and the clearance rate was 0.1 L/h/kg. Most of the FCGN was excreted in the feces, while 9.2 % was excreted in the urine, suggesting absorption and metabolism. The pharmacokinetic parameters indicated that the FCGN was absorbed quickly, eliminated slowly, and could remain in the body for a sustained profile. Moreover, ex vivo imaging and quantification of FCGN in tissues revealed that FCGN accumulated in the liver and kidney. Furthermore, oral administration of CGN or KOs for 14 days led to changes in liver and kidney indices. Histological analysis of significant organs revealed hepatocyte necrosis in the liver, renal tubular vacuolization in the kidney, and incomplete colonic epithelial cells. The KOs had a more significant effect on inflammatory cell infiltration than did CGNs. These in vivo findings laid the foundation for the study and application of CGN in food and pharmaceutical applications.


Asunto(s)
Carragenina , Animales , Ratones , Distribución Tisular , Administración Oral , Masculino , Hígado/metabolismo , Hígado/efectos de los fármacos , Riñón/efectos de los fármacos , Riñón/metabolismo
11.
Int J Biol Macromol ; 267(Pt 2): 131551, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38621566

RESUMEN

Gentiana dahurica Fisch. (G. dahurica) is one of the legitimate sources of Qinjiao in Traditional Chinese Medicine (TCM) and grows on high-altitude plateaus. Plants develop unique biochemical accumulations to resist plateau conditions, especially the strong UV irradiation. Thus, this study aimed to investigate the polysaccharide of G. dahurica (GDP), its structure and its activity against UVB irradiation. Four GDPs were isolated and two of them were subjected to structural elucidation. The results suggested that GDP-1 has 53.5 % Ara and 30.8 % GalA as its main monosaccharides, with a molecular weight (Mw) of 23 kDa; the GDP-2 has 33.9 % Ara and 48.5 % GalA, with a Mw of 82 kDa. Methylation and NMR spectroscopy analysis revealed that GDP-1 contains →5)-α-Araf-(1 â†’ 5)-α-Araf-(1 â†’ 3,5)-α-Araf-(1 â†’ 3,4)-α-GalpA-(6-OMe)-(1→ as the main chain, the branches of GalA (with esterification), and the terminal Ara; the GDP-2 contains →4)-α-GalpA-(1 â†’ 4)-α-GalpA-(6-OMe)-(1 â†’ 5)-α-Araf-(1 â†’ 3,5)-α-Araf-(1→ as the main chain, the branches of →5)-α-Araf-(1-5)-α-Araf, and the terminal GalA. Both GDP-1 and GDP-2 exhibited concentration-dependent antioxidant activity against DPPH, ABTS and hydroxyl radicals. Moreover, GDPs significantly attenuated the decreases in viability and proliferation of HaCaT cells after UVB irradiation. They can scavenge reactive oxygen species (ROS) and improve the activities of endogenous antioxidant enzymes, including superoxide dismutase (SOD) and glutathione peroxidase (GSH). The potential mechanism explored by flow cytometry assays of cell apoptosis and cell cycle distribution suggested that GDPs exert protective effects against UVB irradiation by reducing ROS and attenuating S phase cell arrest. In brief, the GDP-1 and GDP-2 are α-1,3- and α-1,4- arabinogalacturonan, respectively. The high content of Ara could be attributed to biochemical accumulation in resisting to the plateau environment and to prevent UVB irradiation-related damage in cells. These findings provide insight into authentic medicinal herbs and the development of GDPs in the modern pharmaceutical and cosmetics industry.


Asunto(s)
Antioxidantes , Gentiana , Polisacáridos , Rayos Ultravioleta , Polisacáridos/farmacología , Polisacáridos/química , Gentiana/química , Antioxidantes/farmacología , Antioxidantes/química , Humanos , Monosacáridos/análisis , Peso Molecular , Metilación , Protectores contra Radiación/farmacología , Protectores contra Radiación/química , Protectores contra Radiación/aislamiento & purificación
12.
Carbohydr Polym ; 339: 122250, 2024 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-38823917

RESUMEN

Glycyrrhizae Radix et rhizome/licorice is a precious herb in traditional Chinese medicine (TCM). TCM's polysaccharides are medicinally active. But herbal polysaccharides pose some limitations for topical applications. Therefore, this study aimed to utilize licorice polysaccharide via mesoporous silica nanoparticles (MSN) for anti-acne efficacy in topical delivery. The polysaccharide (GGP) was extracted with a 10 % NaOH solution. Chemical characterization suggested that GGP possesses an Mw of 267.9 kDa, comprised primarily of Glc (54.1 %) and Ara (19.12 %), and probably 1,4-linked Glc as a backbone. Then, MSN and amino-functionalized MSN were synthesized, GGP entrapped, and coated with polydopamine (PDA) to produce nanoparticle cargo. The resulted product exhibited 76 % entrapment efficiency and an in vitro release of 89 % at pH 5, which is usually an acne-prone skin's pH. Moreover, it significantly increased Sebocytes' cellular uptake. GGP effectively acted as an anti-acne agent and preserved its efficacy in synthesized nanoparticles. In vivo, the results showed that a 20 % gel of MSN-NH2-GGP@PDA could mediate an inflammatory response via inhibiting pro-inflammatory cytokines and regulating anti-inflammatory cytokines. The MSN-NH2-GGP@PDA inhibited TLR2-activated-MAPK and NF-κB pathway triggered by heat-killed P. acnes. In conclusion, fabricated MSN entrapped GGP for biomimetic anti-acne efficacy in topical application.


Asunto(s)
Acné Vulgar , Glycyrrhiza , Nanopartículas , Polisacáridos , Dióxido de Silicio , Glycyrrhiza/química , Dióxido de Silicio/química , Polisacáridos/química , Polisacáridos/farmacología , Nanopartículas/química , Animales , Porosidad , Acné Vulgar/tratamiento farmacológico , Ratones , Administración Tópica , Humanos , Portadores de Fármacos/química , Liberación de Fármacos , Indoles , Polímeros
13.
Chin J Nat Med ; 22(4): 365-374, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38658099

RESUMEN

Phorbol esters are recognized for their dual role as anti-HIV-1 agents and as activators of protein kinase C (PKC). The efficacy of phorbol esters in binding with PKC is attributed to the presence of oxygen groups at positions C20, C3/C4, and C9 of phorbol. Concurrently, the lipids located at positions C12/C13 are essential for both the anti-HIV-1 activity and the formation of the PKC-ligand complex. The influence of the cyclopropane ring at positions C13 and C14 in phorbol derivatives on their anti-HIV-1 activity requires further exploration. This research entailed the hydrolysis of phorbol, producing seco-cyclic phorbol derivatives. The anti-HIV-1 efficacy of these derivatives was assessed, and the affinity constant (Kd) for PKC-δ protein of selected seco-cyclic phorbol derivatives was determined through isothermal titration calorimetry. The findings suggest that the chemical modification of cyclopropanols could affect both the anti-HIV-1 activity and the PKC binding affinity. Remarkably, compound S11, with an EC50 of 0.27 µmol·L-1 and a CC50 of 153.92 µmol·L-1, demonstrated a potent inhibitory effect on the intermediate products of HIV-1 reverse transcription (ssDNA and 2LTR), likely acting at the viral entry stage, yet showed no affinity for the PKC-δ protein. These results position compound S11 as a potential candidate for further preclinical investigation and for studies aimed at elucidating the pharmacological mechanism underlying its anti-HIV-1 activity.


Asunto(s)
Fármacos Anti-VIH , VIH-1 , VIH-1/efectos de los fármacos , Humanos , Fármacos Anti-VIH/farmacología , Fármacos Anti-VIH/química , Ésteres del Forbol/farmacología , Ésteres del Forbol/química , Estructura Molecular , Proteína Quinasa C/metabolismo , Proteína Quinasa C/química , Relación Estructura-Actividad
14.
Anal Bioanal Chem ; 405(20): 6511-7, 2013 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-23760137

RESUMEN

Comprehensive two-dimensional liquid chromatography (LC × LC) has received much attention because it offers much higher peak capacities than separation in a single dimension. The advantageous peak capacity makes it attractive for the separation of complex samples. Various gradient methods have been used in LC × LC systems. The use of continuous shift gradient is advantageous because it combines the peak compression effect of full gradient mode and the tailed gradient program in parallel gradient mode. Here, a comparison of LC × LC analysis of Chinese herbal medicine with full gradient mode and shift gradient mode in the second dimension was performed. A correlation between the first and second dimensions was found in full gradient mode, and this was significantly reduced with shift gradient mode. The orthogonality increased by 43.7%. The effective peak distribution area increased significantly, which produced better separation.

15.
J Nanosci Nanotechnol ; 13(8): 5924-8, 2013 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-23882861

RESUMEN

Structures and data processing method of the self-developed multi-function and all-electric rheometer (MAR) for polymer composites were introduced. Polypropylene (PP)/Calcium Carbonate (CaCO3) nanocomposites were prepared. And the homogeneity of the composite was characterized by its rheological behavior. With MAR, the effects of vibration parameters on apparent shear viscosity of PP/CaCO3 nanocomposites were investigated. The results show that, the viscosity of the nanocomposites is much lower in dynamic test with proper vibration, comparing with it in corresponding steady-state test at same shear rate. This may be caused by the change of microstructure of the composites under vibration. The shear viscosity sharply decreases with the increase of vibration amplitude. However, the influence of vibration frequency on the shear viscosity of PP/CaCO3 nanocomposites is insignificant. Therefore, it is a good way to increase the superimposed vibration amplitude rather than the frequency to decrease the flow resistance. It is useful for discovering the energy saving mechanic of the polymer processing introduced the vibration energy into.

16.
J Nanosci Nanotechnol ; 13(3): 2339-47, 2013 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-23755689

RESUMEN

Polypropylene (PP) microfiltration membrane were functionalized with an adsorption/surface entrapment process, using block copolymers with poly(n-butyl acrylate) (PBA) as anchor block being capable to tether the pH-responsive block poly(2-(diethylamino) ethyl methacrylate) (PDEA) to the surface, Homopolymer and Block copolymer synthesis was investigated by atom transfer radical polymerization (ATRP) using PMDETA, CuBr and ethyl acetate. These polymers were characterized by 1H NMR and GPC. Copolymer of PDEA with polybutylacrylate (PBA) was selected as best suitable modifier. Models related to the underlying deswelling/entrapment process which leads to fixation of the modifier were considered. Surface properties were analyzed by ATR-FTIR spectroscopy and water contact angle measurements, which confirmed the presence of modifier and a strong improvement of surface and pore wettability. The structure of membranes was evaluated using Polarized Optical Microscopy. Furthermore the pH-sensitive properties of modified PP membranes were verified by pH-dependence of water permeability which due to protonation/deprotonation and volume phase transition of PDEA around the pH 6-6.9.

17.
Luminescence ; 28(3): 412-8, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-22753316

RESUMEN

A carbazole-based compound with intramolecular charge transfer (ICT) characteristics, 3,6-bis-((N-ethylcarbazole-3-)-propene-1-keto)-N-ethylcarbazole (BCzPCz) was synthesized by N-alkylation, acetylation and aldol condensation. BCzPCz was further confirmed by IR and (1)H NMR. The central N-ethylcarbazole was connected with two N-ethylcarbazole units through the propenone group in BCzPCz. N-ethylcarbazole and carbonyl groups were electron donors (D) and acceptors (A), respectively. The UV-vis absorption and fluorescence characteristics of BCzPCz were also investigated in different solvents. Solvatochromism was attributed to ICT complex formation in singlet excited state. Magnitude of the change in the dipole moment was 24.78 D according to Lippert-Mataga equation. Fluorescence of BCzPCz was significantly affected by pH and was quenched in acidic medium. Fluorescence quantum yield of BCzPCz was 0.516 in ethanol. Experimental results showed its potential use as a fluorescence probe and as two-photon absorption material.


Asunto(s)
Carbazoles/química , Colorantes Fluorescentes/química , Fluorescencia , Espectroscopía de Resonancia Magnética , Estructura Molecular
18.
ScientificWorldJournal ; 2013: 320837, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-23766687

RESUMEN

The effects of polytetrafluoroethylene (PTFE), graphite, ultrahigh molecular weight polyethylene (UHMWPE), and their compounds on mechanical and tribological properties of glass-fiber-reinforced polyamide 6 (PA6/GF) were studied. The polymeric materials were blended using twin-screw extruder and subsequently injection molded for test samples. Mechanical properties were investigated in terms of hardness, tensile strength, and impact strength. Friction and wear experiments were run under ambient conditions at a rotating speed of 200 rpm and load of 100 N. The morphologies of the worn surfaces were also observed with scanning electron microscope. The results showed that graphite could increase the tensile strength of PA6/GF-15 composite, but the material became soft. Graphite/UHMWPE complex solid lubricants were effective in increasing the already high impact strength of PA6/GF-15 composite. 5% PTFE gave the maximum reduction in the coefficient of friction. However, PTFE/UHMWPE complex solid lubricants were the best choice for improving both friction and wear behaviors due to the lower friction coefficient and mass wear rate. Moreover, the worn surface of PA6 composites revealed that adhesive wear, abrasive wear, and fatigue wear occurred in this study.


Asunto(s)
Caprolactama/análogos & derivados , Vidrio/química , Grafito/química , Lubricantes/química , Polietilenos/química , Polímeros/química , Politetrafluoroetileno/química , Caprolactama/química , Fricción , Lubrificación , Ensayo de Materiales
19.
Carbohydr Polym ; 316: 121065, 2023 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-37321745

RESUMEN

The lotus (Nelumbo nucifera Gaertn.) is the largest aquatic vegetable in Asia. The lotus seedpod (LS) is an inedible part of the mature flower receptacle of the lotus plant. However, the polysaccharide isolated from the receptacle has been less studied. The purification of LS resulted in two polysaccharides (LSP-1 and LSP-2). Both polysaccharides were found to be medium-sized HG pectin, with a Mw of 74 kDa. Their structures were elucidated via GC-MS and NMR spectrum and proposed as the repeating sugar units of GalA connected via α-1,4-glycosidic linkage, with LSP-1 having a higher degree of esterification. They have certain content of antioxidant and immunomodulatory activities. The esterification of HG pectin would have an adverse effect on these activities. Furthermore, the degradation pattern and kinetics of LSPs by pectinase conformed to the Michaelis-Menten model. There is a large amount of LS, resulting from the by-product of locus seed production, and thus a promising source for the isolation of the polysaccharide. The findings of the structure, bioactivities, and degradation property provide the chemical basis for their applications in the food and pharmaceutical industries.


Asunto(s)
Antioxidantes , Lotus , Antioxidantes/química , Lotus/química , Semillas/química , Polisacáridos/química , Pectinas/análisis
20.
Se Pu ; 41(3): 281-286, 2023 Mar.
Artículo en Zh | MEDLINE | ID: mdl-36861212

RESUMEN

Two-dimensional liquid chromatography (2D-LC) has gained increased attention because of its high peak capacity for separating complex samples. However, preparative 2D-LC aimed at isolating compounds is significantly different compared with one-dimensional liquid chromatography (1D-LC) in terms of method development and system configuration; thus, it is less developed than its analytical counterpart. The use of 2D-LC in large-scale product preparation has rarely been reported. Hence, a preparative 2D-LC system was developed in this study. The system was composed of one set of preparative LC modules as a separation system, with a dilution pump, switch valves, and trap column array as the interface, to enable the simultaneous isolation of several compounds. Tobacco was used as a sample, and the developed system was applied to isolate nicotine, chlorogenic acid, rutin, and solanesol. The chromatographic conditions were developed by investigating the trapping efficiency of different types of trap column packings, and chromatographic behaviors under different overload conditions. The four compounds were isolated in one 2D-LC run with high purity. The developed system features low cost because it employs medium-pressure isolation, excellent automation owing to its use of an online column switch, high stability, and capability for large-scale production. The isolation of chemicals from tobacco leaves as pharmaceutical raw materials could aid in the development of the tobacco industry and promote the local agricultural economy.


Asunto(s)
Ácido Clorogénico , Nicotiana , Cromatografía Liquida , Nicotina , Hojas de la Planta
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