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1.
J Nat Prod ; 2020 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-33216556

RESUMO

Eleven metabolites, six echinosporins (1-6), four dibenzoyls (7-10), and an aromatic compound (11), were isolated from the fermentation broth of lichen-associated Amycolatopsis hippodromi. The structures of the new compounds (1-5, 8-11) were elucidated by comprehensive spectroscopic analysis including data from experimental and calculated ECD spectra. Amycolasporins A-C (1-3) demonstrated antibacterial activities against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli with MIC values of 25 or 100 µg/mL. Amycolasporin C (3) and the known dibenzoyl (7) attenuated the production of NO due to the suppression of the expression of nitric oxide synthase (iNOS) in LPS-induced RAW 264.7 cells in a dose-dependent manner.

2.
Planta Med ; 86(1): 70-77, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31671467

RESUMO

Four new barringtogenol C-type triterpenoid saponins, namely acerplatanosides A - D (1: -4: ), along with 22 known compounds (5: -26: ), were isolated from the stem bark of Norway maple (Acer platanoides). Their structures were elucidated on the basis of comprehensive spectroscopic analyses and chemical hydrolysis. This is the first report of triterpenoid saponins isolated from Norway maple. Compounds 1, 3: , and 4: showed cytotoxicity against 4 human cancer cell lines with IC50 values ranging from 9.4 to 39.5 µM.


Assuntos
Acer/química , Antineoplásicos Fitogênicos/isolamento & purificação , Saponinas/isolamento & purificação , Triterpenos/isolamento & purificação , Antineoplásicos Fitogênicos/química , Linhagem Celular Tumoral , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Estrutura Molecular , Casca de Planta/química , Saponinas/química , Triterpenos/química
3.
J Agric Food Chem ; 67(40): 11089-11098, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31509411

RESUMO

Reactive oxygen species and subsequent oxidative stress are reported to play important roles in chronic metabolic diseases. Plant-derived polyphenols, especially food-derived phenolics, have attracted a lot of attention due to their potential usage against oxidative stress-related diseases. The leaf of Psidium guajava (known as guava) is regarded as a good resource of polyphenols and its products are commercially available in Japan as functional foods against multiple chronic metabolism disorders. In the course of finding novel polyphenols with antioxidative activities from guava leaf, 11 acylated phenolic glycosides (1-11), including 5 new oleuropeic acid-conjugated phenolic glycosides, named guajanosides A-E (1, 2, and 5-7), along with 17 known meroterpenoides (12-28), were isolated and identified. Their structures were determined by spectroscopic data analysis, chemical degradation, and acid hydrolysis. Compounds 1, 2, and 5-11 displayed potent reactive oxygen species-scavenging activity in lipopolysaccharide-stimulated RAW 264.7 macrophage cells. Western blot revealed that compound 6 markedly increased the expression levels of nuclear factor-erythroid 2-related factor 2 (Nrf2), NAD(P)H quinone dehydrogenase 1 (NQO1), and the glutamate-cysteine ligase catalytic subunit. The current study revealed the presence of oleuropeic acid-derived phenolic glycosides in guava leaf and highlighted the potential usage of this type of phenolics against oxidative stress-related metabolic diseases via activation of the Nrf2 signaling pathway.


Assuntos
Depuradores de Radicais Livres/farmacologia , Glicosídeos/farmacologia , Fenóis/farmacologia , Extratos Vegetais/farmacologia , Psidium/química , Espécies Reativas de Oxigênio/metabolismo , Animais , Depuradores de Radicais Livres/química , Glicosídeos/química , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Camundongos , Fator 2 Relacionado a NF-E2/genética , Fator 2 Relacionado a NF-E2/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Fenóis/química , Extratos Vegetais/química , Folhas de Planta/química , Células RAW 264.7
4.
J Chem Phys ; 140(2): 024308, 2014 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-24437878

RESUMO

We conducted a combined anion photoelectron spectroscopy and density functional theory study on V2Si20 cluster. Our results show that the V2Si20 cluster has an elongated dodecahedron cage structure with a V2 unit encapsulated inside the cage. It is the smallest fullerene-like silicon cage and can be used as building block to make cluster-assembled materials, such as pearl-chain style nanowires.

5.
J Chem Phys ; 136(10): 104308, 2012 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-22423839

RESUMO

We conducted a combined anion photoelectron spectroscopy and density functional theory study on the structural evolution of copper-doped silicon clusters, CuSi(n)(-) (n = 4-18). Based on the comparison between the experiments and theoretical calculations, CuSi(12)(-) is suggested to be the smallest fully endohedral cluster. The low-lying isomers of CuSi(n)(-) with n ≥ 12 are dominated by endohedral structures, those of CuSi(n)(-) with n < 12 are dominated by exohedral structures. The most stable structure of CuSi(12)(-) is a double-chair endohedral structure with the copper atom sandwiched between two chair-style Si(6) rings or, in another word, encapsulated in a distorted Si(12) hexagonal prism cage. CuSi(14)(-) has an interesting C(3h) symmetry structure, in which the Si(14) cage is composed by three four-membered rings and six five-membered rings.

6.
Dalton Trans ; 40(11): 2502-8, 2011 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-21290063

RESUMO

Manganese polysulfide cations, MnS(x)(+) (x = 1-10), were studied with mass-selected photodissociation experiments and density functional calculations. We found that MnS(+), MnS(2)(+) and MnS(3)(+) undergo dissociation at 355 nm by loss of S, S(2) and S(3), respectively. The dissociation of larger clusters is relatively complex because of the existence of multiple isomers and multiple dissociation channels. The geometric structures of the low-lying isomers found by theoretical calculations are consistent with the dissociation channels observed in the experiments. The dissociation of MnS(x)(+) clusters occurs mainly by breaking of the Mn-S bonds since they are weaker than the S-S bonds.


Assuntos
Cátions/química , Manganês/química , Modelos Teóricos , Sulfetos/química
7.
J Phys Chem A ; 115(2): 182-6, 2011 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-21155555

RESUMO

We investigated the adsorption of C(2)H radical on small cobalt clusters by mass spectrometry and by measuring the photoelectron spectra of Co(n)C(2)H(-) (n = 1-5) cluster anions. The most stable structures of Co(n)C(2)H(-) (n = 1-5) and their neutrals were determined by comparing the experimental results with theoretical calculations. Our studies show that C(2)H radical still maintains its integrity as a structural unit in Co(n)C(2)H(-) clusters, rather than being divided by Co(n) clusters. The most stable isomers of Co(1-2)C(2)H(-) clusters are linear with the C(2)H interacting with only one Co atom, while those of Co(3-5)C(2)H(-) cluster anions are quasi-planar structures with the carbon-carbon bonds bending slightly toward the Co(3-5) clusters. The carbon-carbon bond of C(2)H is lengthened more in Co(3-5)C(2)H(-) clusters than in Co(1-2)C(2)H(-).

8.
J Phys Chem A ; 115(1): 13-8, 2011 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-21141973

RESUMO

Small aluminum-vanadium oxide clusters, AlVO(y)(-) (y = 1-3) and Al(x)VO(2)(-) (x = 2, 3), were investigated with anion photoelectron spectroscopy and density functional calculations. The adiabatic detachment energies of AlVO(y)(-) were estimated to be 1.06 ± 0.05, 1.50 ± 0.08, and 2.83 ± 0.08 eV for y = 1, 2, and 3. Those of Al(2)VO(2)(-) and Al(3)VO(2)(-) were estimated to be 1.22 ± 0.08 and 1.25 ± 0.08 eV. Comparison of theoretical calculations with experimental measurement suggests that the most probable structure of AlVO(-) cluster is quasilinear with O atom in the middle. AlVO(2)(-) has an irregular chain structure of Al-O-V-O and a C(2v) cyclic structure very close in energy. The structure of AlVO(3)(-) cluster is evolved from the C(2v) cyclic AlVO(2)(-) structure by adding the third O atom to the V atom. Al(2)VO(2)(-) has a pair of nearly degenerate Al-O-V-O-Al chain structures that can be considered as cis and trans forms. Al(3)VO(2)(-) probably has two low-lying isomers each containing a four-membered ring. The structures of the corresponding neutral clusters are discussed.

9.
J Chem Phys ; 133(15): 154314, 2010 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-20969393

RESUMO

Small titanium-aluminum oxide clusters, TiAlO(y) (-) (y=1-3) and TiAl(2)O(y) (-) (y=2-3), were studied by using anion photoelectron spectroscopy. The adiabatic detachment energies of TiAlO(y) (-) (y=1-3) were estimated to be 1.11±0.05, 1.70±0.08, and 2.47±0.08eV based on their photoelectron spectra; those of TiAl(2)O(2) (-) and TiAl(2)O(3) (-) were estimated to be 1.17±0.08 and 2.2±0.1eV, respectively. The structures of these clusters were determined by comparison of density functional calculations with the experimental results. The structure of TiAlO(-) is nearly linear with the O atom in the middle. That of TiAlO(2) (-) is a kite-shaped structure. TiAlO(3) (-) has a kite-shaped TiAlO(2) unit with the third O atom attaching to the Ti atom. TiAl(2)O(2) (-) has two nearly degenerate Al-O-Ti-O-Al chain structures that can be considered as cis and trans forms. TiAl(2)O(3) (-) has two low-lying isomers, kite structure and book structure. The structures of these clusters indicate that the Ti atom tends to bind to more O atoms.

10.
J Chem Phys ; 132(16): 161103, 2010 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-20441250

RESUMO

We investigated Al(n)S(-) (n=3-15) and Al(n)S(2)(-) (n=7-15) clusters with mass spectrometry and photoelectron spectroscopy. We found that Al(13) is relatively robust when it reacts with sulfur atoms, indicating that it has some superatomic character. However, Al(13) cannot be simply considered as a superatom when it interacts with sulfur due to the following reasons: Al(13)'s icosahedral structure has been distorted slightly by sulfur atoms; the vertical detachment energies and adiabatic detachment energies of Al(13)S(-) and Al(13)S(2)(-) clusters are not significantly different from those of their neighboring clusters; and the charge distributions in Al(13)S(-) and Al(13)S(2)(-) do not necessarily associate with superatomic behavior of Al(13).

11.
J Chem Phys ; 132(7): 074308, 2010 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-20170228

RESUMO

We conducted a study of Fe(n)BO(2)(-) clusters by mass spectrometry and photoelectron spectroscopy. The vertical detachment energies and adiabatic detachment energies of these clusters were evaluated from their photoelectron spectra. We have also performed density-functional calculations of Fe(n)BO(2)(-) (n=1-5) clusters and determined their structures by comparison of theoretical calculations to experimental results. The studies show that BO(2) moiety still maintains its linear structure as the bare BO(2) cluster. BO(2) behaves as a superhalogen. Analysis of molecular orbitals reveals that the highest occupied molecular orbitals of Fe(n)BO(2)(-) clusters are mainly localized on the Fe(n) units.

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