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1.
Sci Total Environ ; 712: 136563, 2020 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-31945521

RESUMO

Triclosan (TCS), widely used as an antimicrobial ingredient, is usually introduced into soil by biosolids application, and has presented potential risk in agro-ecosystem. The dissipation pathways of TCS in soil were analyzed in the presence and absence of earthworms (including Metaphire guillelmi and Eisenia fetida). Meanwhile the accumulation and transformation potentials of TCS in the two earthworms were evaluated. Results indicated that about 44% of initial TCS amount dissipated in sterile soil after 56-day incubation, which may mainly result from the bound-residues formation. In contrast, TCS in non-sterile soil dissipated more quickly with a t1/2 of 12 days, suggesting that microbial degradation was responsible for TCS dissipation. Triclosan was methylated to methyl triclosan (MTCS) in soil, which however contributed little for TCS dissipation. The presence of M. guillelmi accelerated TCS dissipation with the reduced t1/2 to 8 days, and inhibited MTCS formation in soil, while E. fetida had no significant (P > 0.05) effects on the fate of TCS. E. fetida accumulated more TCS than M. guillelmi, with bioaccumulation factors up to 11 vs. 0.6. It was also proved that methylation metabolism occurred in earthworms (including gut microorganisms), and M. guillelmi had higher metabolic efficiency compared to E. fetida. Even though eliminations of TCS and MTCS were rapid (except for TCS in M. guillelmi), the residues of the two compounds in both earthworms remained at high levels, having the potential to transfer in the terrestrial food web. In addition, results showed that biosolids application changed TCS persistence, as well as bioavailability dependent on earthworm species. When biosolids at 1% added, more residual TCS and MTCS in soil were observed, while TCS accumulation in E. fetida decreased, however, methylation metabolism in both earthworm species was not affected. The findings provide important information for a more precise risk assessment of biosolids land-application. CAPSULE: Triclosan dissipation, methylation and bioavailability in soils were affected by biosolids amendment and dependent on earthworm species with different accumulation and metabolic potentials.

2.
Sci Total Environ ; 685: 976-985, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31390715

RESUMO

Secondary organic aerosol (SOA) species formed in atmospheric aqueous phases is recently recognized as an important contributor to fine aerosols, which is known to be a prominent human health risk factor internationally. This work, for the first time, systematically investigated aqueous-phase photochemical oxidation of 4-ethylphenol (4-EP) - a model compound from biomass burning and a surrogate of intermediate volatility organic compounds, under both ultraviolet (UV) (Hg lamp) and simulated sunlight (Xe lamp). We found that 4-EP could degrade upon hydroxal radical (OH) oxidation under UV light nearly 15 times faster than that under simulated sunlight, but large aqueous SOA (aqSOA) yields (108%-122%) were observed under both situations. AqSOA masses and oxidation states continuously increased under simulated sunlight, yet they increased first then decreased quickly under UV light. We proposed a reaction scheme based on identified products, showing that oligomerization, functionalization and fragmentation all can occur during 4-EP oxidation. Our results demonstrate that OH radical may suppress oligomerization and functionalization, but is favorable for fragmentation. Under UV light with H2O2 (high OH), fragmentation was dominant, producing more volatile and smaller molecules, and less aqSOA in later oxidation; Under simulated sunlight with H2O2 (moderate OH), functionalization that can form hydroxylated monomer was more important. Moreover, 4-EP oxidation by the organic triplet excited state (3C*) could form species with stronger visible light absorptivity than those from OH-mediated oxidation, and the absorptivity showed positive link with contents of humic-like substances.

3.
Nat Protoc ; 13(4): 605-632, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29494576

RESUMO

Asymmetric catalysis is a powerful approach for the synthesis of optically active compounds, and visible light constitutes an abundant source of energy to enable chemical transformations, which are often triggered by photoinduced electron transfer (photoredox chemistry). Recently, bis-cyclometalated iridium(III) and rhodium(III) complexes were introduced as a novel class of catalysts for combining asymmetric catalysis with visible-light-induced photoredox chemistry. These catalysts are attractive because of their unusual feature of chirality originating exclusively from a stereogenic metal center, which offers the prospect of an especially effective asymmetric induction upon direct coordination of the substrate to the metal center. As these chiral catalysts contain only achiral ligands, special strategies are required for their synthesis. In this protocol, we describe strategies for preparing two types of chiral-at-metal catalysts, namely the Λ- and Δ-enantiomers (left- and right-handed propellers, respectively) of the iridium complex IrS and the rhodium complex RhS. Both contain two cyclometalating 5-tert-butyl-2-phenylbenzothiazoles in addition to two acetonitrile ligands and a hexafluorophosphate counterion. The two cyclometalated ligands set the propeller-shaped chiral geometry, but the acetonitriles are labile and can be replaced by substrate molecules. The synthesis protocol consists of three stages: first, preparation of the ligand 5-tert-butyl-2-phenylbenzothiazole; second, preparation of salicylthiazoline (used for iridium) and salicyloxazoline (used for rhodium) chiral auxiliaries; and third, the auxiliary-mediated synthesis of the individual enantiopure Λ- and Δ-configured catalysts. This class of stereogenic-only-at-metal complexes is of substantial value in the field of asymmetric catalysis, offering stereocontrolled radical reactions based on visible-light-activated photoredox chemistry. Representative examples of visible-light-induced asymmetric catalysis are provided.


Assuntos
Técnicas de Química Sintética , Complexos de Coordenação/síntese química , Isomerismo , Acetonitrilos/química , Complexos de Coordenação/química , Irídio/química , Luz , Oxirredução , Processos Fotoquímicos , Ródio/química , Tiazóis/química
4.
Chem Sci ; 8(10): 7126-7131, 2017 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-29147543

RESUMO

We report an unusual reaction design in which a chiral bis-cyclometalated rhodium(iii) complex enables the stereocontrolled chemistry of photo-generated carbon-centered radicals and at the same time catalyzes an enantioselective sulfonyl radical addition to an alkene. Specifically, employing inexpensive and readily available Hantzsch esters as the photoredox mediator, Rh-coordinated prochiral radicals generated by a selective photoinduced single electron reduction are trapped by allyl sulfones in a highly stereocontrolled fashion, providing radical allylation products with up to 97% ee. The hereby formed fragmented sulfonyl radicals are utilized via an enantioselective radical addition to form chiral sulfones, which minimizes waste generation.

5.
J Org Chem ; 82(17): 8995-9005, 2017 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-28759724

RESUMO

The enantioselective catalytic alkynylation of aromatic aldehydes is reported using a sterically highly hindered bis-cyclometalated rhodium-based Lewis acid catalyst featuring the octahedral metal as the only stereogenic center. Yields of 58-98% with 79-98% enantiomeric excess were achieved using 1-2 mol % of catalyst. This work complements previous work from our laboratory on the enantioselective alkynylation of 2-trifluoroacetyl imidazoles (Chem. - Eur. J. 2016, 22, 11977-11981) and trifluoromethyl ketones (J. Am. Chem. Soc. 2017, 139, 4322-4325) using catalysts with octahedral metal-centered chirality.

6.
Chemosphere ; 183: 176-185, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28549323

RESUMO

Mass concentrations and chemical compositions of submicron particles (PM1) collected during July 2015 to April 2016 in Changzhou, a city in the Yangtze River Delta region, were systematically investigated for the first time. Specifically, an Aerodyne soot particle aerosol mass spectrometer (SP-AMS) was employed to characterize the water-soluble organic matter (WSOM). The average concentration of PM1 was 63.6 µg m-3, occupying ∼60% of co-collected PM2.5 mass. Water soluble inorganic ions (WSIIs) was the most abundant component with secondary ions (SO42-, NO3- and NH4+) as the dominant species. Organic matter (OM) accounted for 21.6% of PM1, with approximately 80% was water-soluble. Trace metals could constitute up to 3.0% of PM1 mass, and Fe, Al and Zn were the three most abundant ones. PAHs were predominated by ones with 5-6 rings, occupying over half of the PAHs mass; further analyses showed that fuel and coal combustion had significant contributions to PAHs. Positive matrix factorization of the WSOM data separated four factors: a traffic-related hydrocarbon-like OA (HOA), a local OA (LOA) likely associated with cooking and coal combustion emissions, etc., a secondary nitrogen-enriched OA (NOA) and an oxygenated OA (OOA). PCA analyses showed that crustal source was likely important for PM1 too. Back trajectory results implied that both PM1 and PM2.5 were mainly derived from local/regional emissions. Our findings present results regarding the PM1 chemistry and its relationship with the PM2.5 in Changzhou, which are valuable for the government to make effective policies to reduce the aerosol pollution in and near the city.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Material Particulado/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Oligoelementos/análise , Aerossóis , China , Cidades , Carvão Mineral/análise , Íons/análise , Espectrometria de Massas/métodos , Tamanho da Partícula , Solubilidade , Fuligem/análise
7.
Huan Jing Ke Xue ; 38(8): 3110-3119, 2017 Aug 08.
Artigo em Chinês | MEDLINE | ID: mdl-29964916

RESUMO

A total of 55 ambient fine particle (PM2.5) samples were collected in Changzhou City from January to August 2016. The concentrations of 17 PM2.5-bound PAHs in the samples were analyzed by GC-MS. Results showed that seasonal average mass concentrations of PAHs in winter, spring, and summer were 140.24, 41.42, and 2.96 ng·m-3, respectively, which indicating that the pollution of PAHs in winter appeared more serious than in the other two seasons, and 4-6-ring high molecular weight PAHs were predominant in all three seasons. The average daily level of BaP was 3.64 ng·m-3 and the days it exceeded the permitted standard accounted for 41% of total days. PAH concentration had significant negative correlations with temperature (correlation coefficient: -0.643) and visibility (correlation coefficient: -0.466), whereas it had good positive correlations with atmospheric pressure (correlation coefficient: 0.544) and poor correlations with wind speed and relative humidity. PAH concentrations were higher at nighttime than at daytime, because of the influences of temperature difference, atmospheric stratification, as well as pollution sources. The results from the air backward trajectory model indicated that PM2.5-bound PAHs in Changzhou were mainly affected by local emission sources and short-distance transportation, whereas the contribution of long-distance transmission was small (only 11%). Based on analysis of characteristic ratios, PAHs were mainly sourced from coal burning, vehicle emissions, and biomass burning. An incremental lifetime cancer risk (ILCR) model was used to evaluate the health impact of PAHs via breathing exposure pathways. Results revealed that the ILCR of adults was higher than that of children. The ILCRs of the group for winter and spring were slightly higher than the risk threshold, but a difference was not obvious for summer.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Material Particulado/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Estações do Ano , Adulto , Criança , China , Cidades , Exposição Ambiental/análise , Humanos , Medição de Risco
8.
Angew Chem Int Ed Engl ; 55(12): 4064-8, 2016 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-26890255

RESUMO

The first total synthesis of the alkaloid (-)-haliclonin A is reported. The asymmetric synthesis relied on a novel organocatalytic asymmetric conjugate addition of nitromethane with 3-alkenyl cyclohex-2-enone to set the stereochemistry of the all-carbon quaternary stereogenic center. The synthesis also features a Pd-promoted cyclization to form the 3-azabicyclo[3,3,1]nonane core, a SmI2 -mediated intermolecular reductive coupling of enone with aldehyde to form the requisite secondary chiral alcohol, ring-closing alkene and alkyne metathesis reactions to build the two aza-macrocyclic ring systems, and an unprecedented direct transformation of enol into enone.


Assuntos
Diaminas/síntese química , Compostos Macrocíclicos/síntese química , Catálise
9.
PLoS One ; 10(9): e0137810, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26368803

RESUMO

High concentrations of arsenic, which can be occasionally found in drinking water, have been recognized as a global health problem. Exposure to arsenic can disrupt spatial memory; however, the underlying mechanism remains unclear. In the present study, we tested whether exercise could interfere with the effect of arsenic exposure on the long-term memory (LTM) of object recognition in mice. Arsenic (0, 1, 3, and 10 mg/ kg, i.g.) was administered daily for 12 weeks. We found that arsenic at dosages of 1, 3, and 10 mg/kg decreased body weight and increased the arsenic content in the brain. The object recognition LTM (tested 24 h after training) was disrupted by 3 mg/ kg and 10 mg/ kg, but not 1 mg/ kg arsenic exposure. Swimming exercise also prevented LTM impairment induced by 3 mg/ kg, but not with 10 mg/ kg, of arsenic exposure. The expression of brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP-response element binding protein (pCREB) in the CA1 and dentate gyrus areas (DG) of the dorsal hippocampus were decreased by 3 mg/ kg and 10 mg/ kg, but not by 1 mg/ kg, of arsenic exposure. The decrease in BDNF and pCREB in the CA1 and DG induced by 3 mg/ kg, but not 10 mg/ kg, of arsenic exposure were prevented by swimming exercise. Arsenic exposure did not affect the total CREB expression in the CA1 or DG. Taken together, these results indicated that swimming exercise prevented the impairment of object recognition LTM induced by arsenic exposure, which may be mediated by BDNF and CREB in the dorsal hippocampus.


Assuntos
Arsênico/efeitos adversos , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Proteína de Ligação a CREB/metabolismo , Transtornos da Memória/prevenção & controle , Condicionamento Físico Animal/métodos , Animais , Arsênico/farmacologia , Comportamento Animal , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Modelos Animais de Doenças , Regulação da Expressão Gênica/efeitos dos fármacos , Masculino , Transtornos da Memória/etiologia , Transtornos da Memória/fisiopatologia , Memória de Longo Prazo/efeitos dos fármacos , Camundongos , Natação/fisiologia
10.
Org Biomol Chem ; 12(18): 2859-63, 2014 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-24675877

RESUMO

We demonstrated, for the first time, that on the basis of chemistry principles, the hexacyclic peptidyl alkaloid (−)-chaetominine (1) can be synthesized in a straightforward manner from L-Trp. The approach features the efficient generation of molecular complexity via a tandem C3/C14 syn-selective epoxidation (dr = 3:2)­annulative ring-opening reaction and a regioselective epimerization at C14. The successful production of (−)-chaetominine (1) from L-Trp could be helpful for revealing how the configuration of L-tryptophan becomes inverted in the biosynthetic pathway of (−)-chaetominine (1).


Assuntos
Vias Biossintéticas , Química Orgânica/métodos , Alcaloides Indólicos/química , Alcaloides Indólicos/síntese química , Triptofano/química , Peptídeos Cíclicos/síntese química , Peptídeos Cíclicos/química
11.
Chem Commun (Camb) ; 50(16): 1986-8, 2014 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-24413776

RESUMO

The total synthesis of the alkaloid (-)-chaetominine (1) has been achieved in four steps with an overall yield of 33.4%. Key features of our strategy include a one-pot cascade indole epoxidation - epoxide ring-opening cyclization - lactamization reaction sequence, and the use of a nitro group as a latent amino group for the one-pot construction of the quinazolinone ring. This constitutes a step economical, redox economical and protecting group-free total synthesis.


Assuntos
Alcaloides Indólicos/síntese química , Alcaloides Indólicos/química , Conformação Molecular , Estereoisomerismo
12.
Chemistry ; 19(1): 87-91, 2013 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-23225701

RESUMO

Three keys to success: A concise method for the construction of a tricyclic substructure (2) of haliclonin A (1) in racemic form is described (see figure). This synthesis features a new Pd-mediated chemoselective carbonyl-enone coupling reaction, an organocatalytic reaction, and a ring-closing metathesis reaction for the construction of the macrocyclic ring as key steps.


Assuntos
Diaminas/química , Diaminas/síntese química , Compostos Macrocíclicos/química , Compostos Macrocíclicos/síntese química , Ciclização , Estereoisomerismo
13.
Cancer Cell ; 17(6): 560-73, 2010 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-20541701

RESUMO

Nonsteroidal anti-inflammatory drugs (NSAIDs) exert their anticancer effects through cyclooxygenase-2 (COX-2)-dependent and independent mechanisms. Here, we report that Sulindac, an NSAID, induces apoptosis by binding to retinoid X receptor-alpha (RXRalpha). We identified an N-terminally truncated RXRalpha (tRXRalpha) in several cancer cell lines and primary tumors, which interacted with the p85alpha subunit of phosphatidylinositol-3-OH kinase (PI3K). Tumor necrosis factor-alpha (TNFalpha) promoted tRXRalpha interaction with the p85alpha, activating PI3K/AKT signaling. When combined with TNFalpha, Sulindac inhibited TNFalpha-induced tRXRalpha/p85alpha interaction, leading to activation of the death receptor-mediated apoptotic pathway. We designed and synthesized a Sulindac analog K-80003, which has increased affinity to RXRalpha but lacks COX inhibitory activity. K-80003 displayed enhanced efficacy in inhibiting tRXRalpha-dependent AKT activation and tRXRalpha tumor growth in animals.


Assuntos
Anti-Inflamatórios não Esteroides/metabolismo , Anti-Inflamatórios não Esteroides/farmacologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptor X Retinoide alfa/antagonistas & inibidores , Transdução de Sinais/efeitos dos fármacos , Sulindaco/análogos & derivados , Sulindaco/farmacologia , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Linhagem Celular , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/genética , Citoplasma/metabolismo , Dinoprostona/metabolismo , Desenho de Drogas , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Modelos Moleculares , Neoplasias/tratamento farmacológico , Neoplasias/metabolismo , Neoplasias/patologia , Fosfatidilinositol 3-Quinases/metabolismo , Prostaglandina-Endoperóxido Sintases/efeitos dos fármacos , Prostaglandina-Endoperóxido Sintases/metabolismo , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/fisiologia , Processamento de Proteína Pós-Traducional/fisiologia , Receptor X Retinoide alfa/genética , Receptor X Retinoide alfa/metabolismo , Deleção de Sequência/fisiologia , Transdução de Sinais/fisiologia , Sulindaco/metabolismo , Sulindaco/uso terapêutico , Ativação Transcricional/efeitos dos fármacos , Transfecção , Tretinoína/farmacologia , Fator de Necrose Tumoral alfa/farmacologia , Ensaios Antitumorais Modelo de Xenoenxerto , Proteína X Associada a bcl-2/genética , Proteína X Associada a bcl-2/metabolismo
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