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1.
Chem Pharm Bull (Tokyo) ; 70(3): 230-234, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35228387

RESUMEN

The details of incompatibility between aripiprazole (ARIP) oral solution and green tea were examined. When the ARIP oral solution was mixed with a commercial PET bottled green tea beverage, the residual rate of ARIP in the mixed solution decreased to 15.7-17.6%. Mixing with ARIP reduced the content of gallate-type green tea polyphenols (GTPs) in the mixed solution but not the content of non-gallate-type GTPs. Furthermore, using pH 3.0 lactic acid buffer, 2.23 mM ARIP solution and 2.23 mM GTP solution were prepared, and the same volumes of ARIP solution and GTP solution were mixed. When the gallate-type GTP solution was mixed, the residual rate of ARIP in the mixed solution decreased. On the other hand, when the non-gallate-type GTP solution was mixed, the residual rate of ARIP in the mixed solution did not decrease. From the above results, it was found that the main reason for the incompatibility between ARIP oral solution and green tea was the formation of an insoluble substance composed of ARIP and gallate-type GTPs in green tea. Furthermore, experimental results using the continuous variation method revealed that ARIP and (-)-epigallocatechin gallate, which is the most representative gallate-type GTP, interact at a molar ratio of 3 : 2.


Asunto(s)
Catequina , Preparaciones Farmacéuticas , Antioxidantes , Aripiprazol , Polifenoles , Té/química
2.
J Chem Phys ; 151(7): 074703, 2019 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-31438713

RESUMEN

The excited-state dynamics of molecular aggregates are governed by their potential energy landscape that can hardly be controlled artificially. However, it is possible to alter the excited state dynamics by a strong coupling between light and molecules (polariton formation) because it can decouple the electronic and vibrational degrees of freedom. Here, we demonstrate this polaron decoupling effect on the photochemical dynamics in singlet fission (SF) of amorphous rubrene thin films embedded in optical microcavities. The vibronic feature of polariton states in this system is characterized through the analysis of steady state absorption spectra by using the Holstein-Tavis-Cummings model. On the basis of this analysis, we show with time-resolved spectroscopy that the SF rate following a resonant excitation of the lowest energy polariton state is indeed modulated when the cavity photon energy is changed. A numerical simulation by using Fermi's golden rule formula with the vibronic polariton feature successfully accounts for the observed modulation of the SF rate, indicating that the polaron decoupling plays a decisive role in the nonadiabatic dynamics.

3.
Genes Cells ; 22(2): 160-173, 2017 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-28097745

RESUMEN

The structural protein Core of hepatitis C virus (HCV), a cytosolic protein, induces endoplasmic reticulum (ER) stress and unfolded protein response (UPR) in hepatocytes, and is responsible for the pathogenesis of persistent HCV infection. Using yeast as a model system, we evaluated mechanisms underlying Core-induced interference of ER homeostasis and UPR, and found that UPR is induced by the immature Core (aa 1-191, Core191) but not by the mature Core (aa 1-177, Core177). Interestingly, Core191 inhibits both ERAD-L, a degradation system responsible for misfolded/unfolded proteins in the ER lumen, and ERAD-M, a degradation system responsible for proteins carrying a misfolded/unfolded region in the ER membrane. In contrast, Core177 inhibits ERAD-M but not ERAD-L. In addition, requirement of an unfolded protein sensor in the ER lumen suggested that inhibition of ERAD-L is probably responsible for Core191-dependent UPR activation. These results implicate inadequate maturation of Core as a trigger for induction of ER stress and UPR.


Asunto(s)
Degradación Asociada con el Retículo Endoplásmico/fisiología , Hepacivirus/metabolismo , Saccharomyces cerevisiae/virología , Respuesta de Proteína Desplegada/fisiología , Proteínas del Núcleo Viral/metabolismo , Animales , Citosol/metabolismo , Retículo Endoplásmico/metabolismo , Estrés del Retículo Endoplásmico , Humanos , Proteínas de la Membrana/metabolismo , Pliegue de Proteína , Saccharomyces cerevisiae/metabolismo
4.
Angew Chem Int Ed Engl ; 57(19): 5438-5443, 2018 05 04.
Artículo en Inglés | MEDLINE | ID: mdl-29516597

RESUMEN

A set of flapping acene dimers fused with an 8π cyclooctatetraene (COT) ring showed distinct excited-state dynamics in solution. While the anthracene dimer showed a fast V-shaped-to-planar conformational change within 10 ps in the lowest excited singlet state, reminding us of extended Baird aromaticity, the tetracene dimer and the pentacene dimer underwent intramolecular singlet fission (SF) in different manners: A fast and reversible SF with a characteristic delayed fluorescence (FL), and a fast and quantitative SF, respectively. Conformational flexibility of the fused COT linkage plays an important role in these ultrafast dynamics, demonstrating the utility of the flapping molecular series as a versatile platform for designing photofunctional systems.

5.
Intern Med ; 63(12): 1683-1687, 2024 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-38494719

RESUMEN

Objective To survey the epidemiology of respiratory pathogens during the coronavirus disease 2019 (COVID-19) pandemic using multiplex polymerase chain reaction (PCR). Methods Specimens were assayed using multiplex nested PCR. Materials Specimens were obtained from outpatients who presented with symptoms of upper respiratory tract infection and asymptomatic outpatients who had contact with patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection at Tohoku Medical and Pharmaceutical University Hospital in Sendai, Japan, from November 1, 2020, to May 31, 2023. The analysis included multiple specimens collected from the same patients at different time-points. Data were collected from the electronic records after testing. Results This study included 8,335 patients (4,311 men) with a median age of 59 years old, and 11,741 total specimens were collected. At least 1 positive SARS-CoV-2 result was obtained for 1,710 (14.6%) specimens. Furthermore, 15 pathogens were identified in the positive specimens, and rhinovirus/enterovirus was detected more frequently than other viruses. We identified a larger number of SARS-CoV-2-positive specimens in patients ≥10 years old. In contrast, in patients 0-9 years old, we identified a larger number of specimens positive for rhinovirus/enterovirus than for other viruses. Conclusion In this study, we examined the epidemiology of circulating respiratory pathogens during the COVID-19 pandemic era.


Asunto(s)
COVID-19 , Infecciones del Sistema Respiratorio , SARS-CoV-2 , Humanos , COVID-19/epidemiología , COVID-19/diagnóstico , Persona de Mediana Edad , Masculino , Femenino , Anciano , Adulto , Japón/epidemiología , Infecciones del Sistema Respiratorio/epidemiología , Infecciones del Sistema Respiratorio/virología , Infecciones del Sistema Respiratorio/diagnóstico , Adolescente , Preescolar , Adulto Joven , Niño , Lactante , Reacción en Cadena de la Polimerasa Multiplex , Anciano de 80 o más Años , Recién Nacido , Pandemias , Rhinovirus/aislamiento & purificación , Rhinovirus/genética
6.
JTO Clin Res Rep ; 5(2): 100639, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38361740

RESUMEN

Histologic transformation is one of the mechanisms of resistance to EGFR tyrosine kinase inhibitor in patients with NSCLC with EGFR mutation. The transformation from adenocarcinoma to squamous cell carcinoma (SCC) has been recently recognized as a mechanism of resistance to osimertinib. The prognosis after transformation to SCC is considered to be poor, and the therapeutic strategy for these patients is unclear. Herein, we report a case of long-term response to pembrolizumab monotherapy for an SCC-transformed lesion in a patient with EGFR-mutated adenocarcinoma after osimertinib treatment. A 68-year-old man underwent right upper lobectomy and was diagnosed with lung adenocarcinoma, pathologic stage IIA, with EGFR L858R. Five years after the surgery, he was diagnosed with recurrence and administered osimertinib. Ten months after, biopsy for an enlarged subpleural lesion revealed SCC with EGFR L858R, leading to a diagnosis of histologic transformation. Notably, the programmed death-ligand 1 expression level of the transformed lesion was higher than that of the adenocarcinoma (90% versus <1%). The size of the SCC lesion had reduced with pembrolizumab monotherapy, and the reduction was maintained for over 47 months since transformation. Nevertheless, the original adenocarcinoma lesion progressed after pembrolizumab therapy and was controlled by other cytotoxic drugs and readministration of osimertinib. Immune checkpoint inhibitor therapy is generally ineffective against EGFR-mutated adenocarcinoma. Nevertheless, it may be promising for achieving a good prognosis when EGFR-mutated adenocarcinoma transforms to SCC after developing EGFR tyrosine kinase inhibitor resistance-particularly if the transformed lesion has high programmed death-ligand 1 expression.

7.
Intern Med ; 63(7): 985-988, 2024 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-37558475

RESUMEN

Nivolumab plus ipilimumab is one of the first-line treatments for advanced non-small-cell lung cancer (NSCLC), but the safety and efficacy in patients on hemodialysis (HD) is unclear. We herein report a patient with NSCLC on HD in whom nivolumab and ipilimumab were initiated. We observed general deterioration and enlarged lesions, followed by a long-term response. The patient developed secondary hypoadrenocorticism, an immune-related adverse event that was easily controlled. Nivolumab plus ipilimumab can be used safely for patients with NSCLC on HD. Long-term effectiveness can be observed after initial progression, so we should carefully assess the response.


Asunto(s)
Carcinoma de Pulmón de Células no Pequeñas , Neoplasias Pulmonares , Humanos , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Nivolumab/uso terapéutico , Ipilimumab/uso terapéutico , Antígeno B7-H1 , Neoplasias Pulmonares/patología , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos
8.
J Phys Chem Lett ; 14(30): 6919-6926, 2023 Aug 03.
Artículo en Inglés | MEDLINE | ID: mdl-37498197

RESUMEN

We report a significantly broad nonlinear optical response enhanced in a tip-substrate plasmonic nanocavity. Focusing on the near-field second harmonics of the wavelength-tunable femtosecond laser, we demonstrate that the tip-enhancement of nonlinear optical effects efficiently works over the broad wavelength range through the visible to infrared region. We also found that this broadband nonlinear optical property is directly affected not only by the nanometer-scale sharpness of the tip apexes but also by the micrometer-scale surface geometry of the tip shafts. While spatially nonlocal plasmonic modes excited throughout the micrometer-scale tip shafts enhance near-to-mid-infrared incoming light, the radiation of visible-to-near-infrared second harmonics is boosted by localized plasmons at the nanogap. These two plasmonic modes simultaneously affect the excitation and emission processes, realizing the strong and broad enhancement of second harmonic generation. Our results provide a new basis for the physical understanding and fine manipulation of nonlinear optical phenomena enhanced in plasmonic nanocavities.

9.
ACS Nano ; 16(7): 10589-10599, 2022 Jul 26.
Artículo en Inglés | MEDLINE | ID: mdl-35758937

RESUMEN

General synthesis of a highly oriented metallic heterodimer array based on a selective electrodeposition technique onto a metal nanoparticle-embedded carbon film is proposed, which enables the preparation of heterodimers with a wide variety of metal combinations. This method requires no surfactant, capping agent, organic solvent, or heat treatment. As a representative metal combination, a nickel (Ni)/palladium (Pd) heterodimer array was prepared by selective electrodeposition of Ni nanoparticles (Ni NPs) on top of partially exposed Pd NPs embedded in carbon film electrodes fabricated by a cosputtering technique. Such a selective electrodeposition becomes possible by utilizing the difference in electrodeposition overpotentials between carbon and Pd NP surfaces. X-ray photoelectron spectroscopy revealed a charge transfer from Ni NPs to Pd NPs, implying that the catalytic and optical properties can be expected to be controllable. The formed heterodimer array structure was mechanically stable against ultrasonication in ethanol for over 1 h because most parts of the Pd NPs were tightly embedded in the carbon film. After conversion from Ni to nickel hydroxide (Ni(OH)2), the electrode showed high electrocatalytic activity toward glucose oxidation, with a higher turnover rate and lower overpotential compared to Ni(OH)2 electrodeposited on pure carbon film electrodes.

10.
Infect Prev Pract ; 4(3): 100221, 2022 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-35677593

RESUMEN

Introduction: Although outbreaks of parainfluenza virus type 3 (PIV-3) have been reported in children, to our knowledge none have been reported in a nursery school. As the symptoms of PIV-3 infection are similar to those of COVID-19 infection, accurate diagnosis of PIV-3 and other respiratory viruses is important during the COVID-19 pandemic. Aims: We experienced an outbreak of upper respiratory symptoms at a nursery school in Miyagi Prefecture, Japan, from 29/5/2021 to 13/6/2021 and aimed to determine the causative organism(s). Methods: A multiplex polymerase chain reaction (PCR) assay which enabled rapid detection of a variety of causative microorganisms of respiratory tract infections was used to analyse 13 nasopharyngeal swabs collected during the outbreak. Infection Prevention and control measures were implemented to prevent further spread of infection. Results: All 13 samples were positive for PIV-3 infection. 2 of the 13 samples were also positive for rhinovirus/enterovirus and 1 sample was also positive rhinovirus/enterovirus and coronavirus NL 63. No samples were positive for SARS-CoV-2. Discussion: Children in school settings are especially vulnerable to respiratory viral infections, including COVID-19. Children under two years are unable to wear masks reliably, and the COVID-19 vaccine was approved only for older children. Multiplex PCR assays can be used for the rapid diagnosis of respiratory infections. Conclusion: We identified an outbreak of PIV-3 in a nursery school during the COVID-19 pandemic. The investigation of the outbreak highlighted that it was important not to overlook other respiratory infections including PIV-3 during the COVID-19 pandemic. The multiplex PCR assay provided rapid and accurate diagnosis of the causative organisms in the outbreak and helped to direct appropriate interventions to control the outbreak.

11.
JAMA Netw Open ; 5(6): e2216393, 2022 06 01.
Artículo en Inglés | MEDLINE | ID: mdl-35687335

RESUMEN

Importance: An adequate system for triaging patients with head trauma in prehospital settings and choosing optimal medical institutions is essential for improving the prognosis of these patients. To our knowledge, there has been no established way to stratify these patients based on their head trauma severity that can be used by ambulance crews at an injury site. Objectives: To develop a prehospital triage system to stratify patients with head trauma according to trauma severity by using several machine learning techniques and to evaluate the predictive accuracy of these techniques. Design, Setting, and Participants: This single-center retrospective cohort study was conducted by reviewing the electronic medical records of consecutive patients who were transported to Tokyo Medical and Dental University Hospital in Japan from April 1, 2018, to March 31, 2021. Patients younger than 16 years with cardiopulmonary arrest on arrival or with a significant amount of missing data were excluded. Main Outcomes and Measures: Machine learning-based prediction models to detect the presence of traumatic intracranial hemorrhage were constructed. The predictive accuracy of the models was evaluated with the area under the receiver operating curve (ROC-AUC), area under the precision recall curve (PR-AUC), sensitivity, specificity, and other representative statistics. Results: A total of 2123 patients (1527 male patients [71.9%]; mean [SD] age, 57.6 [19.8] years) with head trauma were enrolled in this study. Traumatic intracranial hemorrhage was detected in 258 patients (12.2%). Among several machine learning algorithms, extreme gradient boosting (XGBoost) achieved the mean (SD) highest ROC-AUC (0.78 [0.02]) and PR-AUC (0.46 [0.01]) in cross-validation studies. In the testing set, the ROC-AUC was 0.80, the sensitivity was 74.0% (95% CI, 59.7%-85.4%), and the specificity was 74.9% (95% CI, 70.2%-79.3%). The prediction model using the National Institute for Health and Care Excellence (NICE) guidelines, which was calculated after consultation with physicians, had a sensitivity of 72.0% (95% CI, 57.5%-83.8%) and a specificity of 73.3% (95% CI, 68.7%-77.7%). The McNemar test revealed no statistically significant differences between the XGBoost algorithm and the NICE guidelines for sensitivity or specificity (P = .80 and P = .55, respectively). Conclusions and Relevance: In this cohort study, the prediction model achieved a comparatively accurate performance in detecting traumatic intracranial hemorrhage using only the simple pretransportation information from the patient. Further validation with a prospective multicenter data set is needed.


Asunto(s)
Traumatismos Craneocerebrales , Hemorragia Intracraneal Traumática , Algoritmos , Estudios de Cohortes , Traumatismos Craneocerebrales/complicaciones , Traumatismos Craneocerebrales/diagnóstico , Humanos , Aprendizaje Automático , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Estudios Retrospectivos , Triaje/métodos
12.
Anal Sci ; 37(2): 377-380, 2021 Feb 10.
Artículo en Inglés | MEDLINE | ID: mdl-32921650

RESUMEN

This study reports on the electrochemical analysis of coffee extractions at different roasting levels by using a carbon nanotube (CNT) electrode. The roasting levels, ranging from 1 (low) to 6 (high), were determined according to the roasting time after fixing the roasting temperature. Level 1 roasting resulted in light roasted beans and level 6 in dark roasted ones. Based on the roasting level, the concentration of chlorogenic acids, including 3-caffeoylquinic (3CQ), 4-caffeoylquinic (4CQ), and 5-caffeoylquinic (5CQ) acid, can be determined. Cyclic voltammetry (CV) experiments revealed that the reduction current at +0.27 V was proportional to the concentration of chlorogenic acids. High-performance liquid chromatography (HPLC) revealed an inverse correlation between the roasting level and chlorogenic acid amount. The total amounts of chlorogenic acids in coffee extractions determined by HPLC were in agreement with those obtained by CV using the CNT electrode at roasting levels 1 - 5. At level 6, the amount of chlorogenic acids determined by the current peak was larger than that detected by HPLC. As a result, the chlorogenic acid amount was overestimated in the CV experiment at +0.27 V, indicating that electrochemically active materials were generated at level 6. The CV profile showed that the reduction peak at +0.10 V increased with an increase in roasting level. Thus, the peak intensity at +0.10 V can be used to evaluate the roasting level even if the concentration or dilution conditions are provided.


Asunto(s)
Café/química , Técnicas Electroquímicas , Nanotubos de Carbono/química , Extractos Vegetales/análisis , Electrodos
13.
Anal Sci ; 37(1): 37-47, 2021 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-33071269

RESUMEN

Carbon materials have been widely used for electrochemical analysis and include carbon nanotubes, graphene, and boron-doped diamond electrodes in addition to conventional carbon electrodes, such as those made of glassy carbon and graphite. Of the carbon-based electrodes, carbon film has advantages because it can be fabricated reproducibly and micro- or nanofabricated into electrodes with a wide range of shapes and sizes. Here, we report two categories of hybrid-type carbon film electrodes for mainly electroanalytical applications. The first category consists of carbon films doped or surface terminated with other atoms such as nitrogen, oxygen and fluorine, which can control surface hydrophilicity and lipophilicity or electrocatalytic performance, and are used to detect various electroactive biochemicals. The second category comprises metal nanoparticles embedded in carbon film electrodes fabricated by co-sputtering, which exhibits high electrocatalytic activity for environmental and biological samples including toxic heavy metal ions and clinical sugar markers, which are difficult to detect at pure carbon-based electrodes.


Asunto(s)
Carbono/química , Electroquímica/instrumentación , Electrodos , Propiedades de Superficie
14.
RSC Adv ; 11(22): 13311-13315, 2021 Apr 07.
Artículo en Inglés | MEDLINE | ID: mdl-35423851

RESUMEN

The supporting effect of a N-doped carbon film induced superior crystallinity in electrodeposited Ni@Ni(OH)2 core-shell nanoparticles. This improvement resulted in a much higher regeneration rate of catalytic sites (NiOOH), leading to higher oxidation currents of sugars. Also, the overpotential of the maltopentaose (G5) oxidation reaction decreased significantly, probably due to the effect of the electrostatic interaction between NPs and G5.

15.
J Phys Chem Lett ; 11(4): 1349-1356, 2020 Feb 20.
Artículo en Inglés | MEDLINE | ID: mdl-32017569

RESUMEN

The coupling between an electronic system and an environmental bath plays a decisive role in the excited state dynamics of artificial/natural molecular condensed phases. Although it is generally difficult to control the coupling between the system and the thermal bath in condensed matter, a strong light-matter coupling can control system-bath coupling properties using the polaron decoupling effect, in which a coherent interaction between excitons and photons reduces the reorganization energy. Here we demonstrate that this polaron decoupling strongly reduces the fluctuations in electronic energy in tetraphenyldibenzoperiflanthene thin films embedded in an optical microcavity. Using two-dimensional electronic spectroscopy, the frequency-fluctuation correlation function of the lower polariton state was revealed, showing that the dynamic inhomogeneity due to bath coupling inside the microcavity almost vanishes completely. This was attributed to a significant delocalization of the lower polariton state over 105 molecules in the cavity, reducing the effective coupling strength of the bath modes.

16.
Anal Sci ; 36(9): 1113-1118, 2020 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-32378522

RESUMEN

Herein, an electrochemical method is presented for the detection of curcumin in food using a carbon nanotube (CNT)-carboxymethylcellulose (CMC) electrode. The CNT-CMC electrode exhibited ideal characteristics for curcumin detection, namely, a high response current and adequate peak separation toward curcumin oxidation. Cyclic voltammetry revealed two oxidation peaks. In the first scan, only the irreversible peak (Peak I) was observed at a higher potential. In the second scan, the reversible redox peak pairs (Peaks II and II') appeared at lower potentials, and the potential of Peak I was decreased. Peak I corresponded to oxidation of the hydroxyl groups of the benzene ring to the catechol group via a phenoxy radical, while Peaks II and II' indicated the redox loop system of the generated catechol group. The current at Peak II was used to quantify the concentration of curcumin in the linear range of 1 - 48 µM and detection limit of 0.084 µM. The concentrations of curcumin determined by the CNT-CMC electrode in real food samples were consistent with those determined by high-performance liquid chromatography.


Asunto(s)
Carboximetilcelulosa de Sodio/química , Curcumina/análisis , Electroquímica/instrumentación , Análisis de los Alimentos/instrumentación , Nanotubos de Carbono/química , Electrodos , Oxidación-Reducción
17.
Food Chem ; 300: 125189, 2019 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-31325754

RESUMEN

Since the intake of quercetin glucosides has healthy benefits, the analysis of quercetin glucosides in food is useful. The electrochemical determination of individual quercetin glucosides (quercetin-3-glucoside (Q3G), quercetin-4'-glucoside (Q4'G), and quercetin-3,4'-diglucoside (Q34'G)) in food is carried out. For the detection of quercetin glucosides, a long-length carbon nanotube electrode offers attractive properties such as well-defined current peaks, high sensitivity, and high reproducibility. Cyclic voltammetry (CV) demonstrates distinct and specific peak currents: the oxidation peaks at +0.37, +0.45, and +0.78 V are assigned to the catechol group in the B-ring of Q3G, the 3-hydroxy group in the C-ring of Q4'G, and the resorcinol group in the A-ring of both Q4'G and Q34'G, respectively. Currents, which are determined by CV, of individual quercetin glucosides at the peak potential are proportional to the concentrations of onion, apple peel, and tartary buckwheat, which show good agreement with those obtained by high-performance liquid chromatography.


Asunto(s)
Técnicas Electroquímicas/instrumentación , Electrodos , Análisis de los Alimentos/métodos , Glucósidos/análisis , Quercetina/análisis , Técnicas Electroquímicas/métodos , Fagopyrum/química , Análisis de los Alimentos/instrumentación , Malus/química , Nanotubos de Carbono , Cebollas/química , Oxidación-Reducción , Quercetina/análogos & derivados , Quercetina/química , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
18.
Anal Sci ; 35(5): 529-534, 2019 May 10.
Artículo en Inglés | MEDLINE | ID: mdl-30606903

RESUMEN

An electrochemical analysis of polyphenols (theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3'-gallate (TF2B), theaflavin-3,3'-digallate (TF3), and epigallocatechingallate (EGCG)) in a black tea infusion is demonstrated. The characterization of each polyphenol in a solution containing only a single type of polyphenol for a redox reaction at the CNT electrode with cyclic voltammetry (CV) was conducted. The oxidation peak at around +0.30 V for TF1 is assigned to catechol group in a benzotropolone ring. The oxidation peak at around +0.35 V for TF2A, TF2B, and TF3 is assigned to both of the catechol groups in the benzotropolone ring and the pyrogallol group in the gallate ring. The oxidation peak at around +0.35 V for EGCG is assigned to a pyrogallol group in the gallate ring. Current changes of those individual polyphenols at the peak potential are proportional to their concentrations (linear range 0.28 - 94 µM; detection limit 0.11 µM). The CV curve for real black tea, which is mainly composed of a mixture of the mentioned five compounds, is produced by the sum of those. The current change of the mixture solution of polyphenols is also proportional to the mass concentration of the total polyphenols and the sensitivity defined as the slope of current vs. concentration plot is independent of the ratio of the individual polyphenols. This indicates that the peak current at around +0.35 V can quantify the total amount of polyphenols in a black tea. Additionally, the shape of the CV curve can roughly estimate the ratio of [catechins]/[theaflavins]. The values for real samples determined from CVs show good agreement with that obtained by high-performance liquid chromatography.


Asunto(s)
Técnicas Electroquímicas , Nanotubos de Carbono/química , Polifenoles/análisis , Té/química , Electrodos , Conformación Molecular
19.
J Agric Food Chem ; 67(3): 943-954, 2019 Jan 23.
Artículo en Inglés | MEDLINE | ID: mdl-30598043

RESUMEN

We demonstrate the electrochemical quantification of individual catechins (epicatechin, EC; epigallocatechin, EGC; epicatechingallate, ECG; and epigallocatechingallate, EGCG) in a green tea infusion without a separation process nor any adsorption complication. In the detection of catechins, long-length carbon nanotube (CNT)-carboxymethylcellulose (CMC) thin-film electrodes have attractive properties, such as well-defined current peaks, high reproducibility from sample to sample, high repeatability, and low background current. Cyclic voltammograms (CVs) for real green tea, which is mainly composed of a mixture of the four catechins, are produced by the sum of those catechins. A set of three specific peaks in the CVs of the real green tea samples, as catechin-mixture solutions, was used for quantification of the individual catechins. The CVs of the real samples are similar to the CVs of intentionally prepared mixture solutions with the catechin-component ratios determined by high-performance liquid chromatography (HPLC). The values for the real samples determined from the CVs show good agreement with those obtained by HPLC. The novelty of the work is the demonstration of the usefulness of the CNT-CMC electrode and the separationless quantification of individual catechins in green tea for the first time.


Asunto(s)
Camellia sinensis/química , Catequina/química , Catequina/aislamiento & purificación , Técnicas Electroquímicas/métodos , Nanotubos de Carbono/química , Extractos Vegetales/química , Extractos Vegetales/aislamiento & purificación , Té/química , Adsorción , Carboximetilcelulosa de Sodio/química , Cromatografía Líquida de Alta Presión , Técnicas Electroquímicas/instrumentación , Electrodos
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