Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 49
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Anal Chem ; 92(2): 2316-2322, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31859491

RESUMO

Analyte-responsive chromo-fluorogenic reactions under accessible conditions are important for designing small-molecule spectroscopic probes. We describe a series of newly constructed motifs based on the chromo-fluorogenic reaction between catechol derivatives (typically hydroxytyrosol, dopamine, and levodopa) and naphthoresorcin (NR) in aqueous solution under ambient conditions. The weakly absorptive and fluorogenic catechols/NR was converted to products having visible absorption and bright fluorescence within several minutes. The chromo-fluorophores produced from this reaction had a maximum absorbance at 458 nm and emission at 480 nm with high fluorescence quantum yields (30-84%). Inspired by the tyrosinase-catalyzed hydroxylation of monophenols to catechols, the tyrosinase-enabled chromo-fluorogenic reaction was verified by using monophenol (typically tyrosol) as the substrate. In this regard, a dual-readout tyrosinase activity assay was developed by virtue of the in situ "turn-on" optical signals. Furthermore, a test of tyrosinase inhibition, by using a common inhibitor kojic acid, demonstrated the potential of the chromo-fluorogenic reaction for developing other tyrosinase related assays and signal transduction.

2.
J Org Chem ; 84(22): 14679-14687, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31631666

RESUMO

In addition to the 1,9- and 1,7-C60 adducts, the 1,23-C60 adducts are an important type of C60 derivatives, where the property of the fullerene compounds is significantly affected by the addition pattern. However, much less is known on the adducts due to the less availability of the compounds. Herein, the hydroxide-promoted reactions of C60 with 2-alkylmalonates are reported, which produce the 1,23-C60 adducts with improved efficiency. The reactions were studied with the in situ vis-NIR spectral measurement in order to probe into the reaction mechanism. The obtained 1,23-C60 adducts exhibited good thermal stability and better solubility with respect to the 1,7-isomers.

3.
J Food Sci Technol ; 56(2): 811-823, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30906039

RESUMO

Fermented sausages have a long tradition originating from China. In this study, three starter microorganisms including Pediococcus pentosaceus (P), Staphylococcus xylosus (S), and a combination of P. pentosaceus and S. xylosus (P + S) were conducted for the manufacture of traditional Xiangxi (a city in China) fermented sausages. The physicochemical changes of the above three kinds of sausages during fermentation were studied and discussed, and also compared with these properties on the natural fermented sausage (N, i.e., control). The results revealed that five kinds of bacterial phases were existed at different fermentation stages in N, P, S and P + S fermented sausages, respectively. The microbiological data showed that an initial enterobacteria count of approximately 5.3 log CFU/g for all four batches of sausages. The enterobacteria count in the inoculated sausages of P and P + S groups decreased significantly to about 1 log CFU/g whereas group N and S had a count of about 3.3 log CFU/g after fermentation. In the early stages of fermentation, the pH rapidly decreased below 5.3. FAA and FFA were significantly increased in all groups and TBARS value in group P was higher than that of the other three groups. In conclusion, starter cultures can be used to improve the hygiene level of Xiangxi sausages without significant effects on pH, AW, and nitrite residue.

4.
J Org Chem ; 84(6): 3045-3054, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30794405

RESUMO

Aerobic oxidation reaction of [70]fullerene with aliphatic primary thiols in the presence of n-butylamine was studied. The reaction afforded both the fullerene dithiol (2) and dithiol epoxide (3) compounds, which were characterized by 1H and 13C NMR, HRMS and UV-vis spectroscopies. In situ vis-NIR spectral measurement showed absorption bands due to anionic fullerene species, indicating that the reaction was likely initiated with the addition of thiolate anions to C70. Computational calculations were performed to rationalize the structure of the dithiol epoxide compounds. The electrochemical property of 2,5-( n-C5H11S)2C70 (2a) was compared with two analogue compounds of 2,5-Bn2C70 and 2-MeO-5-BnC70 that had identical addition pattern and number of addends. The result showed that the dithiol compound was more electron deficient than the other two derivatives.

5.
J Org Chem ; 83(22): 13716-13725, 2018 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-30352153

RESUMO

Three C70 tetraadducts, 2,10-(MeO)2-5,9-Bn2C70 (6), 1,56-Bn2-2,57-(MeO)2C70 (7, 2 o'clock isomer), and 1,41-Bn2-2,58-(MeO)2C70 (8, 12 o'clock isomer), were obtained from the reaction of C70 with MeO- and BnBr (benzyl bromide). The structures of 6-8 were resolved via single-crystal X-ray diffraction and spectroscopic characterizations. Computational calculations on the electrophilic Fukui functions fk+, the stability of reaction intermediates, and activation barriers for the key processes of the reaction were performed to rationalize the regioselectivity of the reaction. A conversion of the 5 and 12 o'clock intermediates to the 2 o'clock intermediate was proposed to account for the regioselectivity related to the 2-fold additions at the two distinctive polar regions of C70. Electrochemical study showed a similar electron deficiency for the 2 and 12 o'clock isomers, while the 2,5,9,10-tetraadduct was more electron deficient with respect to the 2 and 12 o'clock isomers.

6.
Org Lett ; 20(12): 3591-3595, 2018 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-29851491

RESUMO

A reactivity pattern for C3-arylation of 9-MeO-phenanthrene has been established for the first time by using 2-naphthyl amines as coupling partners. A series of phenanthrene- and naphthalene-based multifunctionalized polycyclic aromatic hydrocarbons have been obtained in good to excellent yields. Alternative C10-arylation of 9-MeO-phenanthrene has also been accomplished, using 2-naphthalenol derivatives as coupling partners. Trifluoroacetic acid is found crucial for the regioselectivity. Density functional theory calculations and electrochemical analyses have been performed to rationalize the reaction mechanism.

7.
Org Lett ; 20(8): 2328-2332, 2018 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-29634273

RESUMO

Controlled synthesis of the equatorial tetra-, hexa-, and octaorgano[70]fullerenes with mixed addends was achieved via the reaction of equatorial 7,23-Bn2C70 with MeO- and ArCH2Br. The products were structurally characterized by single crystal X-ray diffraction. The regioselectivity of the reaction was studied by in situ vis-NIR and Fukui function analysis. A surprising electrophilic triorgano[70]fullerene carbanion was shown, and an enhanced fluorescence was observed for the mixed octaadducts.

8.
Research (Wash D C) ; 2018: 1936735, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-31549024

RESUMO

Organic electrode materials are receiving ever-increasing research interest due to their combined advantages, including resource renewability, low cost, and environmental friendliness. However, their practical applications are still terribly plagued by low conductivity, poor rate capability, solubility in electrolyte, and low density/utilization of active groups. In response, herein, as a proof-of-concept experiment, C=N and C=O bonds are synergically integrated into the backbone of pentacene to finely tune the electronic structures of pentacene. Unexpectedly, the firstly obtained unique 5,7,11,14-tetraaza-6,13-pentacenequinone/reduced graphene oxide (TAPQ/RGO) composite exhibits superior electrochemical performances, including an ultra-stable cycling stability (up to 2400 cycles) and good rate capability (174 mAh g-1 even at a high current density of 3.2 A g-1), which might be attributed to the abundant active groups, π-conjugated molecular structure, leaf-like morphology, and the interaction between TAPQ and graphene.

9.
J Org Chem ; 82(16): 8676-8685, 2017 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-28731698

RESUMO

C60 o-quinodimethane bisadducts [C60(QM)2] are promising electron acceptors for bulk heterojuction (BHJ) organic solar cells (OSCs). However, previous production of C60(QM)2 often resulted in excessive regioisomers, which were difficult to purify and might consequently obscure the structure-performance study of the organofullerene acceptors. Herein, the electrosynthesis of C60(QM)2 is reported. The reaction exhibits a strong regiocontrol with generation of fewer regioisomers. Pure regioisomers of cis-2, trans-3, and e C60(QM)2 are obtained, and the structures are solved with single-crystal X-ray diffraction. Interestingly, the cis-2 and trans-3 regioisomers exhibit better photovoltaic performance than the e regioisomer in the OSCs based on poly(3-hexylthiophene) (P3HT), which can be correlated with their structural difference.

10.
J Org Chem ; 82(17): 9253-9257, 2017 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-28748692

RESUMO

The C70 δ-adducts with closed [5,6]-ring fusion are an important type of compound in classifying bond delocalization in the equatorial belt of C70. However, the formation of such compounds is severely restricted due to the low reactivity of the carbon atoms in the flat equatorial region. Such a restriction is lifted when reduced anionic C70 species are used, where the inert equatorial carbon atoms are activated.

11.
J Zhejiang Univ Sci B ; 18(4): 324-333, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28378570

RESUMO

Xiangxi flavor vinegar (XV) is one of Hunan Province's traditional fermented vinegars. It is produced from herb, rice, and spring water with spontaneous liquid-state fermentation techniques. In this study, we investigated the antioxidant property of XV by analyzing its antioxidant compounds, its free radical scavenging property in vitro and in vivo, and its effects on antioxidant enzyme activity and apoptosis in Caenorhabditis elegans. The results showed that XV is rich in antioxidants. In particular, ligustrazine reached 6.431 µg/ml. The in vitro 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH•), hydroxyl radical (•OH), and superoxide anion radical (O2•-) scavenging rates of XV were 95.85%, 97.22%, and 63.33%, respectively. The reactive oxygen species (ROS) content in XV-treated C. elegans decreased significantly (P<0.01) compared to the control group. Glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) activities were remarkably increased (P<0.01) in C. elegans after XV treatment. In addition, XV could upregulate CED-9 protein expression and downregulate CED-3 protein expression in C. elegans. These results prove that XV is rich in antioxidants and scavenges radicals in vitro efficiently. XV inhibits apoptosis in C. elegans probably by scavenging ROS and increasing the activities of its antioxidant enzymes.


Assuntos
Ácido Acético/farmacologia , Antioxidantes/farmacologia , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/metabolismo , Análise de Alimentos , Animais , Antioxidantes/análise , Apoptose/efeitos dos fármacos , Caenorhabditis elegans/citologia , Proteínas de Caenorhabditis elegans/metabolismo , Caspases/metabolismo , Catalase/metabolismo , China , Fermentação , Depuradores de Radicais Livres/farmacologia , Glutationa Peroxidase/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Pirazinas/análise , Pirazinas/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismo
12.
Angew Chem Int Ed Engl ; 55(36): 10662-6, 2016 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-27485314

RESUMO

Polydopamine (PDA), which is biodegradable and is derived from naturally occurring products, can be employed as an electrode material, wherein controllable partial oxidization plays a key role in balancing the proportion of redox-active carbonyl groups and the structural stability and conductivity. Unexpectedly, the optimized PDA derivative endows lithium-ion batteries (LIBs) or sodium-ion batteries (SIBs) with superior electrochemical performances, including high capacities (1818 mAh g(-1) for LIBs and 500 mAh g(-1) for SIBs) and good stable cyclabilities (93 % capacity retention after 580 cycles for LIBs; 100 % capacity retention after 1024 cycles for SIBs), which are much better than those of their counterparts with conventional binders.


Assuntos
Fontes de Energia Elétrica , Indóis/química , Lítio/química , Polímeros/química , Sódio/química , Condutividade Elétrica , Eletrodos , Desenho de Equipamento , Íons/química , Modelos Moleculares , Oxirredução
13.
J Org Chem ; 81(15): 6838-42, 2016 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-27387300

RESUMO

Methoxylation of the singly bonded 1,4-1',4'-BnC60-C60Bn dimer afforded 1,4-OMe(Bn)C60, a 1,4-C60 adduct with sterically less demanding addends, as the major adduct. The situation was different from that of direct functionalization of C60, where 1,2-OMe(Bn)C60 was obtained as the major product. The reaction was studied with in situ vis-NIR spectroscopy and computational calculations to obtain a better understanding of this unusual regioselectivity. The stability difference between 1,2- and 1,4-OMe(Bn)C60 was studied.

14.
Chem Commun (Camb) ; 52(33): 5710-3, 2016 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-27039948

RESUMO

C70 multiadducts with a novel 1,2,3,4,41,56,57,58-configuration were prepared via oxazolination and benzylation reactions. The structures of the adducts were determined by single crystal X-ray diffraction and spectral characterization. The compounds exhibit a high LUMO level, and result in a high open-circuit voltage in devices with P3HT.

15.
Anal Chem ; 88(2): 1355-61, 2016 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-26703206

RESUMO

We demonstrate a rationally designed fluorescent and colorimetric dual-readout strategy for the highly sensitive, quantitative determination of inorganic pyrophosphatase (PPase) activity, a key hydrolytic enzyme involved in a variety of metabolic processes. Inspired by the selective oxidative and chromogenic reaction of o-phenylenediamine (OPD) with Cu(2+), the special inhibitory effects of pyrophosphate (PPi) on the oxidative ability of Cu(2+), and the specific hydrolysis of PPi into orthophosphate by PPase, a convenient small molecule OPD-based analytical system was developed for Cu(2+)/PPi recognition and PPase activity assay. We have confirmed that Cu(2+) acts as the oxidant in the reaction and the main chromogenic product of OPD is 2,3-diaminophenazine (usually called OPDox) in the assay by combining the ESI-MS, (1)H NMR, and XPS spectra analysis. Direct electrochemical insights into the Cu(2+)-triggered and PPi-inhibited mechanism were performed by cyclic voltammetry characterizations of the Cu(2+) in the absence and presence of PPi for the first time. Furthermore, the proposed analytical system with clear response mechanism exhibits a promising outlook for the PPase activity assay in real biological samples and inhibitor screening.


Assuntos
Colorimetria/métodos , Cobre/química , Pirofosfatase Inorgânica/análise , Fenilenodiaminas/química , Cobre/metabolismo , Cobre/farmacologia , Difosfatos/química , Difosfatos/metabolismo , Difosfatos/farmacologia , Fluorescência , Pirofosfatase Inorgânica/metabolismo , Estrutura Molecular , Oxirredução/efeitos dos fármacos , Fenilenodiaminas/metabolismo , Fosfatos/metabolismo
16.
J Org Chem ; 81(1): 121-8, 2016 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-26587878

RESUMO

The base-promoted oxidative cycloaddition reaction of [60]fullerene with ethyl acetoacetate was investigated. The reaction resulted in C60 bis-2',3'-dihydrofuran derivatives, but only with the trans-1, trans-2, trans-3, and e configurations rather than any cis or trans-4 structures, demonstrating a new regioselectivity resulting from steric influence on C60 bisaddition. In addition, distribution of the bisadducts was complicated by the unsymmetrical nature of the addends, where each individual configuration may consist of several regioisomers.

17.
J Zhejiang Univ Sci B ; 16(12): 1019-26, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26642185

RESUMO

This study investigates the long-term effects of oral tea polyphenols (TPs) and Lactobacillus brevis M8 (LB) on biochemical parameters, digestive enzymes, and cytokines expression in broilers. In experiment 1, 240 broiler chickens were selected to investigate the effects of 0.06 g/kg body weight (BW) TP and 1.0 ml/kg BW LB on broilers; in experiment 2, 180 broiler chickens were assigned randomly to three groups to investigate the effects of different dosages of TP (0.03, 0.06, and 0.09 g/kg BW) combined with 1.0 ml/kg BW LB on broilers; in experiment 3, 180 broiler chickens were assigned randomly to three groups to investigate the effects of different dosages of LB (0.5, 1.0, and 1.5 ml/kg BW) combined with 0.06 g/kg BW TP on broilers. The results showed that TP and LB affected serum biochemical parameters, and TP reduced serum cholesterol (CHO) and low-density lipoprotein cholesterol (LDL-C) abundances in a dosage-dependent manner (P<0.05) on Day 84. Meanwhile, broilers fed a diet supplemented with TP or LB had a lower intestinal lipase activity on Day 84 compared with the control group (P<0.05). Middle and high dosages of TP increased pancreatic lipase and proventriculus pepsin activities (P<0.05). Also middle and high dosages of LB significantly enhanced pancreatic lipase activity (P<0.05), while high LB supplementation inhibited intestinal trypsase (P<0.05) on Day 84. Furthermore, both TP and LB reduced intestinal cytokine expression and nuclear factor-κ B (NF-κB) mRNA level on Days 56 and 84. In conclusion, long-term treatment of TP and LB improved lipid metabolism and digestive enzymes activities, and affected intestinal inflammatory status, which may be associated with the NF-κB signal.


Assuntos
Galinhas/metabolismo , Lactobacillus brevis/fisiologia , Polifenóis/administração & dosagem , Administração Oral , Animais , Glicemia/metabolismo , Galinhas/genética , HDL-Colesterol/sangue , LDL-Colesterol/sangue , Citocinas/genética , Digestão/efeitos dos fármacos , Relação Dose-Resposta a Droga , Expressão Gênica/efeitos dos fármacos , Intestinos/efeitos dos fármacos , Intestinos/enzimologia , Probióticos/administração & dosagem , Chá/química , Triglicerídeos/sangue
18.
Org Lett ; 17(21): 5192-5, 2015 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-26468767

RESUMO

[60]Fullerene derivatives with novel 1,4,9,25- and 1,4,9,12-configurations were obtained by reactions of C60 with aliphatic ketones and benzyl bromide under basic conditions. The structures of the products were determined by X-ray single-crystal diffraction and spectroscopic characterization. The reactions were rationalized by a monoenolate addition experiment and in situ vis-NIR spectroscopy.

19.
J Phys Chem A ; 119(36): 9534-40, 2015 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-26291551

RESUMO

Reduced fullerenes and fullerene derivatives exhibit intense absorptions in the vis-near-IR (vis-NIR) region. The absorptions are sensitive toward the addition pattern, number of addends, and oxidation state of the fullerene species and are used as an important benchmark for identifying anionic fullerene species. Similar absorptions are also shown for the reduced singly bonded C60 species, which are electronically different from reduced fullerene derivatives. However, much less work has been carried out on the vis-NIR spectroscopic study of the anionic singly bonded C60 species, likely due to the difficulty in controlled production of these species. Herein, we report the vis-NIR spectroscopic study of the mono- and dianions of the singly bonded C60 species (RC60(-), R(-)C60(-), and RC60(2-•)), which are selectively generated by controlled-potential bulk electrolysis (CPE) of the singly bonded C60 dimer and C60 oxazolino heterocycles. Time-dependent density functional theory (TD-DFT) calculations were performed to rationalize the experimental results.

20.
J Org Chem ; 80(10): 5315-9, 2015 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-25905560

RESUMO

C70 bis-heterocyclic derivative (1) bearing one oxazoline ring and one imidazoline ring with the 2 o'clock configuration is obtained with high chemio- and regioselectivity via the reaction of C70 with hydroxide and benzonitrile quenched with I2. Further study with benzylation experiment and theoretical calculations indicate that the oxazoline ring is the one first formed on the C70 cage, while the imidazoline ring is the one formed after the addition of I2 via a radical coupling reaction mechanism.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA