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1.
Viruses ; 16(5)2024 04 25.
Artículo en Inglés | MEDLINE | ID: mdl-38793559

RESUMEN

Coxsackievirus B3 (CVB3) is a positive single-strand RNA genome virus which belongs to the enterovirus genus in the picornavirus family, like poliovirus. It is one of the most prevalent pathogens that cause myocarditis and pancreatitis in humans. However, a suitable therapeutic medication and vaccination have yet to be discovered. Caboxamycin, a benzoxazole antibiotic isolated from the culture broth of the marine strain Streptomyces sp., SC0774, showed an antiviral effect in CVB3-infected HeLa cells and a CVB3-induced myocarditis mouse model. Caboxamycin substantially decreased CVB3 VP1 production and cleavage of translation factor eIF4G1 from CVB3 infection. Virus-positive and -negative strand RNA was dramatically reduced by caboxamycin treatment. In addition, the cleavage of the pro-apoptotic molecules BAD, BAX, and caspase3 was significantly inhibited by caboxamycin treatment. In animal experiments, the survival rate of mice was improved following caboxamycin treatment. Moreover, caboxamycin treatment significantly decreased myocardial damage and inflammatory cell infiltration. Our study showed that caboxamycin dramatically suppressed cardiac inflammation and mouse death. This result suggests that caboxamycin may be suitable as a potential antiviral drug for CVB3.


Asunto(s)
Antivirales , Infecciones por Coxsackievirus , Modelos Animales de Enfermedad , Enterovirus Humano B , Miocarditis , Animales , Miocarditis/tratamiento farmacológico , Miocarditis/virología , Ratones , Infecciones por Coxsackievirus/tratamiento farmacológico , Infecciones por Coxsackievirus/virología , Humanos , Enterovirus Humano B/efectos de los fármacos , Células HeLa , Antivirales/farmacología , Antivirales/uso terapéutico , Masculino , Ratones Endogámicos BALB C , Inflamación/tratamiento farmacológico , Inflamación/virología , Replicación Viral/efectos de los fármacos
2.
Biomol Ther (Seoul) ; 32(4): 492-498, 2024 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-38651201

RESUMEN

Bioassay and HPLC-UV guided fractionations of the crude extract of marine-derived Streptomyces sp. SNA-077 have led to the isolation of a red pigment, undecylprodigiosin (1). The chemical structure of undecylprodigiosin (1) was revealed by the interpretation of NMR and mass spectroscopic (MS) data. Further, anti-melanogenic effects of undecylprodigiosin (1) were investigated. First, the melanin contents of undecylprodigiosin (1)-treated B16 cells were evaluated. Furthermore, undecylprodigiosin (1) significantly inhibited the key enzymes involved in melanogenesis, including tyrosinase, tyrosinase related protein-1 (TYRP-1), and dopachrome tautomerase (DCT). The mRNA and protein expression levels of Microphthalmia-associated transcriptian factor (MiTF), a critical transcription factor for tyrosinase gene expression, were also suppressed by undecylprodigiosin (1) treatment in B16 analyses. Collectively, our results suggest for the first time that undecylprodigiosin (1), a potent component isolated from an extract of marine Streptomyces sp. SNA-077, critically exerts the anti-melanogenic ability for melanin synthesis.

3.
Bioorg Med Chem Lett ; 105: 129737, 2024 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-38599297

RESUMEN

A new monoterpenoid, neoroseoside (1), along with two previously reported compounds, 2″-O-α-l-rhamnosyl-6-C-fucosylluteolin (2) and farobin A (3) were isolated from the Zea mays. The structure of compound 1 was determined through the analysis spectroscopic data, including mass spectrometry (MS), infrared (IR) spectroscopy, and nuclear magnetic resonance (NMR) data. The absolute configurations of 1 were deduced from the comparing the values of optical rotations and from the interpretation of electronic circular dichroism (ECD) spectra. Compounds 2 and 3 displayed moderate antibacterial activity against Streptococcus mutans ATCC 25175 (inhibition rates 24 % and 28 %, respectively) and Streptococcus sobrinus ATCC 33478 (inhibition rate of 26 %), at a concentration of 100 µg/mL, whereas compound 1 did not have any significant antibacterial activities. The compounds 1-3 also showed anti-inflammatory activity on cytokine IL-6 and TNF-α.


Asunto(s)
Antibacterianos , Pruebas de Sensibilidad Microbiana , Monoterpenos , Zea mays , Zea mays/química , Antibacterianos/farmacología , Antibacterianos/química , Antibacterianos/aislamiento & purificación , Monoterpenos/farmacología , Monoterpenos/química , Monoterpenos/aislamiento & purificación , Antiinflamatorios/farmacología , Antiinflamatorios/química , Antiinflamatorios/aislamiento & purificación , Relación Estructura-Actividad , Estructura Molecular , Streptococcus mutans/efectos de los fármacos , Interleucina-6/metabolismo , Interleucina-6/antagonistas & inhibidores , Descubrimiento de Drogas , Factor de Necrosis Tumoral alfa/antagonistas & inhibidores , Factor de Necrosis Tumoral alfa/metabolismo , Relación Dosis-Respuesta a Droga , Streptococcus/efectos de los fármacos
4.
Biomol Ther (Seoul) ; 32(2): 231-239, 2024 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-38296651

RESUMEN

Methyl anthranilate (MA) is a botanical fragrance used in food flavoring with unexplored potential in anti-pigment cosmetics. MA dose-dependently reduced melanin content without affecting cell viability, inhibited dendrite elongation and melanosome transfer in the co-culture system of human melanoma cells (MNT-1) and human keratinocyte cell line (HaCaT), and downregulated melanogenic genes, including tyrosinase, tyrosinase-related protein 1 and 2 (TRP-1, TRP-2). Additionally, MA decreased cyclic adenosine monophosphate (cAMP) production and exhibited a significant anti-pigmentary effect in Melanoderm™. These results suggest that MA is a promising anti-pigmentary agent for replacing or complementing existing anti-pigmentary cosmetics.

5.
Mar Drugs ; 21(9)2023 Sep 13.
Artículo en Inglés | MEDLINE | ID: mdl-37755102

RESUMEN

A HPLC-UV guided fractionation of the culture broth of Streptomyces sp. CNQ-617 has led to the isolation of a new quinazolinone derivative, actinoquinazolinone (1), as well as two known compounds, 7-hydroxy-6-methoxy-3,4-dihydroquinazolin-4-one (2) and 7-methoxy-8-hydroxy cycloanthranilylproline (3). The interpretation of 1D, 2D NMR, and MS spectroscopic data revealed the planar structure of 1. Furthermore, compound 1 suppressed invasion ability by inhibiting epithelial-mesenchymal transition markers (EMT) in AGS cells at a concentration of 5 µM. In addition, compound 1 decreased the expression of seventeen genes related to human cell motility and slightly suppressed the signal transducer and activator of the transcription 3 (STAT3) signal pathway in AGS cells. Together, these results demonstrate that 1 is a potent inhibitor of gastric cancer cells.

6.
Regul Toxicol Pharmacol ; 142: 105433, 2023 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-37302562

RESUMEN

Cosmetics often contain botanical extracts, which present a challenge for safety assessors due to their complex composition. The threshold of toxicological concern (TTC) approach is considered as a solution for the safety assessment of botanical extracts in cosmetics as part of next-generation risk assessment. In this study, we applied the TTC approach to evaluate the safety of Cnidium officinale rhizome extract (CORE), a widely used botanical extract in skin conditioning products. We identified 32 components of CORE through the USDA database and literature and determined the content of each component through literature or actual analysis where an authentic standard was available. Macro- and micronutrients were also analyzed to exclude them as safe components. The Toxtree® software was used to identify the Cramer class of remaining components. We estimated the systemic exposure of each component from leave-on type cosmetic products containing CORE at a 1% concentration and compared the results to TTC thresholds. All components of CORE had a systemic exposure below the TTC threshold. While batch variations and presence of unknown chemicals in individual CORE materials should be considered, this study demonstrated that the TTC approach can be a useful tool for the safety assessment of botanical extracts in cosmetics.


Asunto(s)
Cnidium , Cosméticos , Nivel sin Efectos Adversos Observados , Rizoma , Programas Informáticos , Cosméticos/toxicidad , Medición de Riesgo
7.
Mar Drugs ; 21(3)2023 Feb 25.
Artículo en Inglés | MEDLINE | ID: mdl-36976200

RESUMEN

Marinobazzanan (1), a new bazzanane-type sesquiterpenoid, was isolated from a marine-derived fungus belonging to the genus Acremonium. The chemical structure of 1 was elucidated using NMR and mass spectroscopic data, while the relative configurations were established through the analysis of NOESY data. The absolute configurations of 1 were determined by the modified Mosher's method as well as vibrational circular dichroism (VCD) spectra calculation and it was determined as 6R, 7R, 9R, and 10R. It was found that compound 1 was not cytotoxic to human cancer cells, including A549 (lung cancer), AGS (gastric cancer), and Caco-2 (colorectal cancer) below the concentration of 25 µM. However, compound 1 was shown to significantly decrease cancer-cell migration and invasion and soft-agar colony-formation ability at concentrations ranging from 1 to 5 µM by downregulating the expression level of KITENIN and upregulating the expression level of KAI1. Compound 1 suppressed ß-catenin-mediated TOPFLASH activity and its downstream targets in AGS, A549, and Caco-2 and slightly suppressed the Notch signal pathway in three cancer cells. Furthermore, 1 also reduced the number of metastatic nodules in an intraperitoneal xenograft mouse model.


Asunto(s)
Antineoplásicos , Sesquiterpenos , Humanos , Animales , Ratones , Células CACO-2 , Transformación Celular Neoplásica , Antineoplásicos/química , Movimiento Celular , Sesquiterpenos/farmacología , Sesquiterpenos/química , Estructura Molecular
8.
Int J Mol Sci ; 24(6)2023 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-36982727

RESUMEN

The AIM2 inflammasome is an innate immune system component that defends against cytosolic bacteria and DNA viruses, but its aberrant activation can lead to the progression of various inflammatory diseases, including psoriasis. However, there have been few reports of specific inhibitors of AIM2 inflammasome activation. In this study, we aimed to investigate the inhibitory activity of ethanolic extracts of seeds of Cornus officinalis (CO), a herb and food plant used in traditional medicine, on AIM2-inflammasome activation. We found that CO inhibited the release of IL-1ß induced by dsDNA in both BMDMs and HaCaT cells, but that it showed no effect on the release of IL-1ß induced by NLRP3 inflammasome triggers, such as nigericin and silica, or the NLRC4 inflammasome trigger flagellin. Furthermore, we demonstrated that CO inhibited the cleavage of caspase-1, an inflammasome activation marker, and an upstream event, the translocation and speck formation of ASC. In addition, further experiments and mechanistic investigations revealed that CO can inhibit AIM2 speck formation induced by dsDNA in AIM2-overexpressing HEK293T cells. To verify the correlation in vivo, we investigated the efficacy of CO in an imiquimod (IMQ)-induced psoriasis model, which has reported associations with the AIM2 inflammasome. We found that topical application of CO alleviated psoriasis-like symptoms, such as erythema, scaling, and epidermal thickening, in a dose-dependent manner. Moreover, CO also significantly decreased IMQ-induced expression of AIM2 inflammasome components, including AIM2, ASC, and caspase-1, and led to the elevation of serum IL-17A. In conclusion, our results suggest that CO may be a valuable candidate for the discovery of AIM2 inhibitors and the regulation of AIM2-related diseases.


Asunto(s)
Cornus , Dermatitis , Psoriasis , Humanos , Inflamasomas/metabolismo , Imiquimod/efectos adversos , Células HEK293 , Psoriasis/inducido químicamente , Psoriasis/tratamiento farmacológico , Inflamación , Extractos Vegetales/efectos adversos , Semillas/metabolismo , Caspasas , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Interleucina-1beta/metabolismo , Caspasa 1/metabolismo , Proteínas de Unión al ADN/metabolismo
9.
Nat Prod Res ; : 1-6, 2023 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-36714927

RESUMEN

The intensive investigation of chemical components from the culture broth of the bacterium Saccharomonospora sp. CNQ-490 has yielded four new natural products, lodopyridones D - G (1 - 4) along with the previously reported compounds, lodopyridones A - C (5 - 7) and cotteslosin A (8). The planar structures of the lodopyridones D - G (1 - 4) were elucidated by interpreting the mass spectrometry, ultraviolet (UV) spectroscopy, and 1D and 2D nuclear magnetic spectroscopy (NMR) data, as well as comparing NMR data with those of the lodopyridones A - C (5 - 7).

10.
Int J Mol Sci ; 23(23)2022 Nov 29.
Artículo en Inglés | MEDLINE | ID: mdl-36499251

RESUMEN

Excess melanin in skin is known to be the main cause of hyper-pigmentary skin diseases such as freckles and lentigo. This study aimed to evaluate the depigmenting efficacy of an extract from the marine microorganism strain, Streptomyces sp. SNA077. To determine the anti-melanogenic efficacy of SNA077, we assessed the melanin contents of SNA077-treated B16, Melan-a, and MNT-1 cells. We observed the expression of key enzymes in melanogenesis via qRT-PCR and Western blot analyses. We further estimated the skin-whitening effect of SNA077 using a skin-equivalent model. SNA077 dramatically decreased the melanin production of B16 cells, Melan-a, and MNT-1 cells. In B16 cells treated with SNA077, the activity of cellular tyrosinase was clearly inhibited. In addition, the mRNA and protein expression levels of melanogenic genes were suppressed by SNA077 treatment in B16 and MNT-1 cells. Upstream of tyrosinase, the expression levels of phospho-CREB, phospho-p38, PKA activity, cyclic AMP production, and MC1R gene expression were inhibited by SNA077. Finally, SNA077 clearly showed a skin-brightening effect with a reduced melanin content in the skin tissue model. Collectively, our results suggest for the first time that an extract of marine Streptomyces sp. SNA077 could be a novel anti-melanogenic material for skin whitening.


Asunto(s)
Melanoma Experimental , Streptomyces , Animales , Melaninas , Streptomyces/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Línea Celular Tumoral , Monofenol Monooxigenasa/metabolismo , Factor de Transcripción Asociado a Microftalmía/genética , Factor de Transcripción Asociado a Microftalmía/metabolismo , Extractos Vegetales/farmacología , Melanoma Experimental/metabolismo
11.
J Antibiot (Tokyo) ; 75(11): 619-625, 2022 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-36109669

RESUMEN

HPLC-UV-guided fractionation of crude extract from the marine sediment-derived bacterium Streptomyces sp. CNP-944 has yielded two new pyrazine alkaloids, actinopolymorphols E and F (1 and 2), in addition to the previously reported biosynthetic product, actinopolymorphol G (3), and the known actinopolymorphol D (4). The chemical structures of 1-3 were determined based on the interpretation of the 1D, 2D NMR, and MS spectroscopic data. Compound 2 displayed weak antibacterial activities against Kocuria rhizophila, Bacillus subtilis, and Staphylococcus aureus with minimum inhibitory concentration (MIC) values of 16, 64, and 64 µg ml-1, respectively.


Asunto(s)
Alcaloides , Streptomyces , Alcaloides/farmacología , Antibacterianos/química , Antibacterianos/farmacología , Mezclas Complejas , Sedimentos Geológicos/microbiología , Pruebas de Sensibilidad Microbiana , Pirazinas/farmacología , Streptomyces/química
12.
Mar Drugs ; 20(2)2022 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-35200684

RESUMEN

The tricyclic quinazoline alkaloid deoxyvasicinone (DOV, 1) was isolated from a marine-derived Streptomyces sp. CNQ-617, and its anti-melanogenic effects were investigated. Deoxyvasicinone was shown to decrease the melanin content of B16F10 and MNT-1 cells that have been stimulated by α-melanocyte-stimulating hormone (α-MSH). In addition, microscopic images of the cells showed that deoxyvasicinone attenuated melanocyte activation. Although, deoxyvasicinone did not directly inhibit tyrosinase (TYR) enzymatic activity, real-time PCR showed that it inhibited the mRNA expression of TYR, tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2 (TRP-2). In the artificial 3D pigmented skin model MelanodermTM, deoxyvasicinone brightened the skin significantly, as confirmed by histological examination. In conclusion, this study demonstrated that the marine microbial natural product deoxyvascinone has an anti-melanogenic effect through downregulation of melanogenic enzymes.


Asunto(s)
Melaninas/metabolismo , Quinazolinas/farmacología , Piel/efectos de los fármacos , Streptomyces/metabolismo , Animales , Línea Celular Tumoral , Regulación hacia Abajo/efectos de los fármacos , Humanos , Melanocitos/efectos de los fármacos , Melanocitos/metabolismo , Melanoma/metabolismo , Melanoma Experimental/metabolismo , Ratones , Quinazolinas/aislamiento & purificación , Piel/metabolismo
13.
ACS Omega ; 7(2): 1722-1732, 2022 Jan 18.
Artículo en Inglés | MEDLINE | ID: mdl-35071867

RESUMEN

A cyclic depsipeptide, nobilamide I (1), along with the known peptide A-3302-B/TL-119 (2), was isolated from the saline cultivation of the marine-derived bacterium Saccharomonospora sp., strain CNQ-490. The planar structure of 1 was elucidated by interpretation of 1D and 2D NMR and MS spectroscopic data. The absolute configurations of the amino acids in 1 were assigned by using the C3 Marfey's analysis and comparing them with those of 2 based on their biosynthetic pathways. Nobilamide I (1) decreased cell motility by inhibiting epithelial-mesenchymal transition markers in A549 (lung cancer), AGS (gastric cancer), and Caco2 (colorectal cancer) cell lines. In addition, 1 modulated the expression of the matrix metalloproteinase (MMP) family (MMP2 and MMP9) in the three cell lines.

14.
Mar Drugs ; 19(11)2021 Oct 30.
Artículo en Inglés | MEDLINE | ID: mdl-34822489

RESUMEN

Four new chlorinated meroterpenoids, merochlorins G-J (1-4), and 10, a dihydronaphthalenedione precursor, along with known merochlorins A (5) and C-F (6-9), were obtained from cultivation of the bacterium strain Streptomyces sp. CNH-189, which was isolated from marine sediment. The planar structures of compounds 1-4 and 10 were elucidated by interpretation of MS, UV, and NMR spectroscopic data. The relative configurations of compounds 1-4 were determined via analysis of nuclear Overhauser effect (NOE) spectroscopic data, after which their absolute configurations were established by comparing the experimental electronic circular dichroism (ECD) spectra of compounds 1-4 to those of previously reported possible enantiomer models and DP4 calculations. Compound 3 displayed strong antibacterial activities against Bacillus subtilis, Kocuria rhizophila, and Staphylococcus aureus, with MIC values of 1, 2, and 2 µg/mL, respectively, whereas compound 1 exhibited weak antibacterial effects on these three strains, with a 16-32 µg/mL MIC value range.


Asunto(s)
Antibacterianos/farmacología , Streptomyces , Terpenos/farmacología , Animales , Antibacterianos/química , Organismos Acuáticos , Bacillus subtilis/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Micrococcaceae/efectos de los fármacos , Staphylococcus aureus/efectos de los fármacos , Terpenos/química
15.
J Fungi (Basel) ; 7(10)2021 Oct 18.
Artículo en Inglés | MEDLINE | ID: mdl-34682298

RESUMEN

Using 126 endogenous lichen fungus (ELF) extracts, inhibitory activities against monoamine oxidases (MAOs) and cholinesterases (ChEs) were evaluated. Among them, extract ELF29 of the endogenous fungus Diaporthe mahothocarpus of the lichen Cladonia symphycarpia showed the highest inhibitory activity against hMAO-A. Compounds alternariol (AT), 5'-hydroxy-alternariol (HAT), and mycoepoxydiene (MED), isolated from the extract, had potent inhibitory activities against hMAO-A with IC50 values of 0.020, 0.31, and 8.68 µM, respectively. AT, HAT, and MED are reversible competitive inhibitors of hMAO-A with Ki values of 0.0075, 0.116, and 3.76 µM, respectively. The molecular docking studies suggested that AT, HAT, and MED had higher binding affinities for hMAO-A (-9.1, -6.9, and -5.6 kcal/mol, respectively) than for hMAO-B (-6.3, -5.2, and -3.7 kcal/mol, respectively). The relative tight binding might result from a hydrogen bond interaction of the three compounds with a Tyr444 residue in hMAO-A, whereas no hydrogen bond interaction was proposed in hMAO-B. In silico pharmacokinetics, the three compounds showed high gastrointestinal absorption without violating Lipinski's five rules, but only MED showed high probability to cross the blood-brain barrier. These results suggest that AT, HAT, and MED are candidates for treating neuropsychiatric disorders, such as depression and cardiovascular disease.

16.
Molecules ; 26(8)2021 Apr 13.
Artículo en Inglés | MEDLINE | ID: mdl-33924656

RESUMEN

Salicornia europaea L. is a halophyte that grows in salt marshes and muddy seashores, which is widely used both as traditional medicine and as an edible vegetable. This salt-tolerant plant is a source of diverse secondary metabolites with several therapeutic properties, including antioxidant, antidiabetic, cytotoxic, anti-inflammatory, and anti-obesity effects. Therefore, this review summarizes the chemical structure and biological activities of secondary metabolites isolated from Salicornia europaea L.


Asunto(s)
Chenopodiaceae/química , Animales , Humanos , Fitoquímicos/química , Plantas Tolerantes a la Sal/química
17.
Mar Drugs ; 20(1)2021 Dec 29.
Artículo en Inglés | MEDLINE | ID: mdl-35049890

RESUMEN

Analysis of the chemical components from the culture broth of the marine bacterium Saccharomonospora sp. CNQ-490 has yielded three novel compounds: saccharobisindole (1), neoasterric methyl ester (2), and 7-chloro-4(1H)-quinolone (3), in addition to acremonidine E (4), pinselin (5), penicitrinon A (6), and penicitrinon E (7). The chemical structures of the three novel compounds were elucidated by the interpretation of 1D, 2D nuclear magnetic resonance (NMR), and high-resolution mass spectrometry (HRMS) data. Compound 2 generated weak inhibition activity against Bacillus subtilis KCTC2441 and Staphylococcus aureus KCTC1927 at concentrations of 32 µg/mL and 64 µg/mL, respectively, whereas compounds 1 and 3 did not have any observable effects. In addition, compound 2 displayed weak anti-quorum sensing (QS) effects against S. aureus KCTC1927 and Micrococcus luteus SCO560.


Asunto(s)
Actinobacteria , Antibacterianos/farmacología , Quinolonas/farmacología , Animales , Antibacterianos/química , Organismos Acuáticos , Bacillus subtilis/efectos de los fármacos , Ésteres , Humanos , Pruebas de Sensibilidad Microbiana , Quinolonas/química
18.
J Nat Prod ; 83(10): 3166-3172, 2020 10 23.
Artículo en Inglés | MEDLINE | ID: mdl-32985880

RESUMEN

A cyclic tetrapeptide, androsamide (1), was isolated from a marine actinomycete of the genus Nocardiopsis, strain CNT-189. The planar structure of 1 was assigned by the interpretation of 1D and 2D NMR spectroscopic data. The absolute configurations of constituent amino acids of 1 were determined by application of the Marfey's and advanced Marfey's methods. Androsamide (1) strongly suppressed the motility of Caco2 cells caused by epithelial-mesenchymal transition.


Asunto(s)
Antibióticos Antineoplásicos/farmacología , Nocardiopsis/química , Aminoácidos/química , Antibióticos Antineoplásicos/síntesis química , Células CACO-2 , Movimiento Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Ensayos de Selección de Medicamentos Antitumorales , Transición Epitelial-Mesenquimal/efectos de los fármacos , Fermentación , Humanos , Espectroscopía de Resonancia Magnética , Estructura Molecular , Invasividad Neoplásica
19.
Sci Rep ; 9(1): 1334, 2019 Feb 04.
Artículo en Inglés | MEDLINE | ID: mdl-30718639

RESUMEN

Hierarchical twinning, at multiple length scales, was noted in a metastable body-centered cubic (bcc) ß-titanium alloy on tensile deformation. Site-specific characterization within the deformation bands, carried out using EBSD and TEM, revealed {332} <113> type primary bcc twins, containing different variants of secondary and tertiary twins, as well as the formation of stress-induced martensite (α"). Within the primary {332} <113> type twin, "destruction" of the prior quenched-in athermal ω phase was observed, while a stress-induced ω phase reforms within the tertiary twins, revealing the intricate nature of coupling between deformation twinning and displacive ω transformation.

20.
Mater Sci Eng C Mater Biol Appl ; 33(4): 2159-67, 2013 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-23498244

RESUMEN

Corrosion behavior of a multifunctional biomedical titanium alloy Ti-24Nb-4Zr-8Sn (wt.%) in 0.9% NaCl, Hank's solution and artificial saliva at 37 °C was investigated using open circuit potential, impedance spectroscopy and potentiodynamic polarization techniques, and some results were compared with pure titanium and Ti-6Al-4V alloy. The results showed that the alloy exhibited good corrosion resistance due to the formation of a protective passive film consisting mainly of TiO2 and Nb2O5, and a little of ZrO2 and SnO2. Ca ions were detected in the passive film as the alloy immersed in Hank's and artificial saliva solutions and they have negative effect on corrosion resistance. The EIS results indicated that either a duplex film with an inner barrier layer and an outer porous layer or a single passive layer was formed on the surface, and they all transformed into stable bilayer structure as the immersion time increased up to 24h. The polarization curves demonstrated that the alloy had a wider passive region than pure titanium and Ti-6Al-4V alloy and its corrosion current density (less than 0.1 µA/cm(2)) is comparable to that of pure titanium.


Asunto(s)
Aleaciones/química , Ensayo de Materiales , Saliva Artificial/química , Corrosión , Espectroscopía Dieléctrica , Electricidad , Técnicas Electroquímicas , Microscopía Electrónica de Rastreo , Espectroscopía de Fotoelectrones , Soluciones , Propiedades de Superficie , Factores de Tiempo , Difracción de Rayos X
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