Involvement of the Keap1-Nrf2-ARE pathway in the antioxidant activity of sinomenine.

Sinomenine is a pure alkaloid isolated from Sinomenium acutum. This study is aimed to investigate the critical role of the nuclear factor erythroid 2-related factor 2 (Nrf2)-kelch-like ECH-associated protein-1(Keap1)-antioxidant response element (ARE) antioxidative signaling pathway in protecting sinomenine against H2O2-induced oxidative injury. Cytotoxicity and antioxidant experiments to initially determine the protective effects of sinomenine show that sinomenine has no effect on the decreased cell viability and presents similar potency in scavenging all three free radicals. The binding affinity between sinomenine and Keap1 was determined via fluorescence polarization assay, with IC50 of 13.52 µM. Quantum chemical calculation and theoretical simulation illustrated that sinomenine located into the Nrf2-binding site of Keap1 via hydrophobic and hydrogen interactions, showing high stability and binding affinity. On the basis of the stable binding of sinomenine with Keap1, sinomenine efficiently induced nuclear translocation of Nrf2, and increased in ARE activity in a concentration-dependent manner. Quantitative polymerase chain reaction provided further evidences that sinomenine-induced protection upregulated ARE-dependent genes, such as NAD(P)H quinone oxidoreductase 1, hemeoxygenase-1, and glutamate-cysteine ligase modifier subunit. Western blot confirmed that sinomenine increased the expressions of these antioxidative enzymes. Taken together, in vitro and in silico evaluations demonstrate that sinomenine inhibits the binding of Keap1 to Nrf2, promotes the nuclear accumulation of Nrf2 and thus leads to the upregulated expressions of Nrf2-dependent antioxidative genes. Our findings also highlight the use of sinomenine for pharmacological or therapeutic regulation of the Nrf2-Keap1-ARE system, which is a novel strategy to prevent the progression of oxidative injury.

Self-Supported 3D PtPdCu Nanowires Networks for Superior Glucose Electro-Oxidation Performance.

The development of non-enzymatic and highly active electrocatalysts for glucose oxidation with excellent durability for blood glucose sensors has aroused widespread concern. In this work, we report a fast, simple, and low-cost NaBH4 reduction method for preparing ultrafine ternary PtPdCu alloy nanowires (NWs) with a 3D network nanostructure. The PtPdCu NWs catalyst presents significant efficiency for glucose oxidation-reduction (GOR), reaching an oxidative peak-specific activity of 0.69 mA/cm2, 2.6 times that of the Pt/C catalyst (0.27 mA/cm2). Further reaction mechanism investigations show that the NWs have better conductivity and smaller electron transfer resistance. Density functional theory (DFT) calculations reveal that the alloying effect of PtPdCu could effectively enhance the adsorption energy of glucose and reduce the activation energy of GOR. The obtained NWs also show excellent stability over 3600 s through a chronoamperometry test. These self-supported ultrafine PtPdCu NWs with 3D networks provide a new functional material for building blood glucose sensors and direct glucose fuel cells.

Preparation of 4-butylaniline-bonded silica gel for the solid-phase extraction of flavone glycosides.

To extract flavone glycosides efficiently, a new extraction material based on 4-butylaniline-bonded silica gel was prepared using a two-step grafting method including a ring-opening reaction and synchronous hydrolysis. Preparation of the silica-based material was easily achieved under mild conditions, and the material was characterized by Fourier transform infrared spectroscopy, elemental analysis, and scanning electron microscopy. The material was used in solid-phase extraction, and the extraction can be performed in neutral conditions without regard to ionic strength. Selectivity tests of 14 compounds on the extraction cartridge showed that the material has a high affinity to flavone glycosides in contrast to octadecyl silica, and the extraction yields for four flavone glycosides were found to be >93%. Selectivity tests further reveal that the adsorption on its surface is likely attributed to multiple interactions, including hydrophobic interactions, π-π interactions, and hydrogen bonding. To explore the applicability of 4-butylaniline-bonded silica gel, naringin and hesperidin from Simotang oral liquid were extracted, and the extraction yields were >90%, which is distinguished from <28% on octadecyl silica cartridge.

Ligand effect of PdRu on Pt-enriched surface for glucose complete electro-oxidation to carbon dioxide and abiotic direct glucose fuel cells.

The development of advanced electrocatalysts for the abiotic direct glucose fuel cells (ADGFCs) is critical in the implantable devices in living organisms. The ligand effect in the Pt shell-alloy core nanocatalysts is known to influence the electrocatalytic reaction in interfacial structure. Herein, we reported the synthesis of ternary Pt@PdRu nanoalloy aerogels with ligand effect of PdRu on Pt-enriched surface through electrochemical cycling. Pt@PdRu aerogels with optimized Pt surface electronic structure exhibited high mass activity and specific activity of Pt@PdRu about 450 mA·mgPt-1 and 1.09 mA·cm-2, which were 1.4 and 1.6 times than that of commercial Pt/C. Meanwhile, Pt@PdRu aerogels have higher electrochemical stability comparable to commercial Pt/C. In-situ FTIR spectra results proved that the glucose oxidation reaction on Pt@PdRu aerogels followed the CO-free direct pathway reaction mechanism and part of the products are CO2 by completed oxidation. Furthermore, the ADGFC with Pt@PdRu ultrathin anode catalyst layer showed a much higher power density of 6.2 mW·cm-2 than commercial Pt/C (3.8 mW·cm-2). To simulate the blood fuel cell, the Pt@PdRu integrated membrane electrode assembly was exposed to glucose solution and a steady-state open circuit of approximately 0.6 V was achieved by optimizing the glucose concentration in cell system.

Rapid prediction method of ZIF-8 immobilized Candida rugosa lipase activity by near-infrared spectroscopy.

Candida rugosa lipase (CRL, EC3.1.1.3) is one of the main enzymes synthesizing esters, and ZIF-8 was chosen as an immobilization carrier for lipase. Enzyme activity testing often requires expensive reagents as substrates, and the experiment processes are time-consuming and inconvenient. As a result, a novel approach based on near-infrared spectroscopy (NIRs) was developed for predicting CRL/ZIF-8 enzyme activity. The absorbance of the immobilized enzyme catalytic system was evaluated using UV-Vis spectroscopy to investigate the amount of CRL/ZIF-8 enzyme activity. The powdered samples' near-infrared spectra were obtained. The sample's enzyme activity data were linked with each sample's original NIR spectra to establish the NIR model. A partial least squares (PLS) model of immobilized enzyme activity was developed by coupling spectral preprocessing with a variable screening technique. The experiments were completed within 48 h to eliminate inaccuracies between the reduction in enzyme activity with increasing laying-aside time throughout the test and the NIRs modeling. The root-mean-square error of cross-validation (RMSECV), the correlation coefficient of validation set (R) value, and the ratio of prediction to deviation (RPD) value were employed as assessment model indicators. The near-infrared spectrum model was developed by merging the best 2nd derivative spectral preprocessing with the Competitive Adaptive Reweighted Sampling (CARS) variable screening method. This model's root-mean-square error of cross-validation (RMSECV) was 0.368 U/g, the correlation coefficient of calibration set (R_cv) value was 0.943, the root-mean-square error of prediction (RMSEP) set was 0.414 U/g, the correlation coefficient of validation set (R) value was 0.952, and the ratio of prediction to deviation (RPD) was 3.0. The model demonstrates that the fitting relationship between the predicted and the reference enzyme activity value of the NIRs is satisfactory. The findings revealed a strong relationship between NIRs and CRL/ZIF-8 enzyme activity. As a result, the established model could be implemented to quantify the enzyme activity of CRL/ZIF-8 quickly by including more variations of natural samples. The prediction method is simple, rapid, and adaptable to be the theoretical and practical basis for further studying other interdisciplinary research work in enzymology and spectroscopy.

Rapid prediction method of α-Glycosidase inhibitory activity of Coreopsis tinctoria extract from different habitats by near infrared spectroscopy.

α-Glucosidase is one of the main enzymes causing elevated blood glucose, and Coreopsis tinctoria extract can be used as a natural inhibitor of α-Glucosidase. Therefore, a new method was proposed for predicting the inhibitory activity on α-Glucosidase of Coreopsis tinctoria extract based on near infrared spectroscopy. The absorbance of the inhibitory system was measured by ultraviolet spectroscopy, which was used to study the inhibitory activity on a-glucosidase of Coreopsis tinctoria extract. The near infrared spectra of the solid samples were collected. By selecting spectral preprocessing and optimizing spectral bands, a rapid prediction model of the inhibitory activity was established by partial least squares regression. The root mean square error of cross-validation (RMSECV), correlation coefficient (R) value and the ratio of prediction to deviation (RPD) value were used as indicators of the evaluation model. The near infrared spectrum model was established by combining the best spectral preprocessing of the continuous wavelet transform (CWT) and the best spectral band. The root mean square error of cross-validation (RMSECV) of this model was 0.815%, the correlation coefficient (R) value was 0.942, and the ratio of prediction to deviation (RPD) was 3.0. The root mean square error of prediction (RMSEP) of the model by prediction set was 0.819%, the correlation coefficient (R) value was 0.950, and the RPD was 3.2. The model shows that the fitting relationship between the predicted inhibition value and the reference inhibition value of the near infrared spectral model is good. The results showed that there was a good correlation between near infrared spectroscopy and the inhibitory activity of Coreopsis tinctoria extract. Thus, the established model was robust and effective and could be used for rapid quantification of α-Glucosidase inhibitory activity. The prediction method is simple and rapid, and can be extended to study the inhibition of other medicinal plants.

Preparation of 4-butylaniline-bonded attapulgite for pre-concentration of bisphenol A in trace quantity.

Ring-opening reaction with synchronous hydrolysis was used to prepare 4-butylaniline-modified attapulgite (abbreviated as BA-ATP) for pre-concentration of bisphenol A (BPA) in trace quantity. The preparation was achieved under mild condition, and the material was characterized by Fourier transform infrared spectroscopy (FT-IR), elemental analysis, nuclear magnetic resonance (NMR) and scanning electron microscopy. BA-ATP was used in solid phase extraction (SPE), and SPE was performed in a neutral condition without regard to ionic strength. The results indicate that BA-ATP has high affinity to BPA with a maximum adsorption amount of 44mg g(-1), and the adsorption can be described by Langmuir isotherm model. The content of bisphenol A in water samples was analyzed by HPLC method with the pre-concentration using BA-ATP. The limit of detection (LOD) can be as low as 3.9ng mL(-1), and the average recoveries are in a range of 93-97% with relative standard deviation (RSD) of less than 2%.

[Determination of rutin, quercetin and kaempferol in Althaea rosea (L) Gavan for Uyghur medicine by high performance liquid chromatography].

Uyghur medicine is one important part of the national medicine system. Uyghur medicine modernization, namely the study of effective components with modern technologies, is the only way for the scientification, standardization, and industrialization of Uyghur medicine. Here we developed a selective extraction method for rutin, quercetin and kaempferol in Althaea rosea (L) Gavan. The three active species were determined by high performance liquid chromatography (HPLC) with HC-C18 column (250 mm x 4.6 mm, 5 µm) and the mobile phase of CH3OH-0.4% H3PO4 (50 :50, v/v). Rutin, quercetin and kaempferol were baseline separated with each other and the interference species with flow rate of 1.0 mL/min and column temperature of 30 degrees C. Under the optimal conditions, linear correlation were obtained in the mass concentration range of 12.5-150 µg/mL (r = 0.999 8) for rutin, 12.5-125 µg/mL (r = 0.999 9) for quercetin, and 12.5-125 µg/mL (r = 0.998 8) for kaempferol. The recoveries (n = 5) of rutin, quercetin and kaempferol were 100.25% ( RSD = 1.1%), 97.60% ( RSD = 0.47%) and 97.75% (RSD = 0.71%), respectively. The method can be used to determine the contents of rutin, quercetin and kaempferol in Althaea rosea (L) Gavan and provide the guidance for the analysis of the flavonoids in other Uyghur medicines.