Screening 5-lipoxygenase inhibitors from selected traditional Chinese medicines and isolation of the active compounds from Polygoni Cuspidati Rhizoma by an on-line bioactivity evaluation system.

To identify natural products as new prototypes for 5-lipoxygenase (5-LOX), 12 traditional Chinese medicines (TCMs) were selected for screening their 5-LOX inhibition activities. The results showed that the methanol extracts of all selected TCMs (n = 12) possessed inhibitory activities against 5-LOX at 200 µg/mL, of which six extracts of the TCMs showed significant inhibitory effects with IC50 values in the range from 33.2 ± 1.4 µg/mL to 153.5 ± 1.7 µg/mL, and the extract of Polygoni Cuspidati Rhizoma (RPC) was the most active sample. An on-line ultra-performance liquid chromatography-photodiode array-MSn -5-LOX-fluorescence detector (UPLC-PDA-MSn -5-LOX-FLD) method was applied to further identify the potential 5-LOX inhibitory constituents in RPC extracts, which resulted in the identification of seven components with 5-LOX-binding activities. Finally, four compounds (polydatin, resveratrol, emodin-8-O-glucoside, and emodin) were successfully purified from RPC extracts. The 5-LOX inhibition action was assayed in vitro, and the results showed that these compounds possessed potent inhibitory effects against 5-LOX with IC50 values of 15.3 ± 2.1, 4.5 ± 1.2, 23.8 ± 0.4, and 11.8 ± 1.5 µg/mL, respectively. This was the first study to reveal the 5-LOX inhibitory constituents of RPC, and the present investigation might provide a valuable approach for the rapid discovery of natural inhibitors from TCMs.

Highly sensitive and selective determination of p-nitrophenol at an interpenetrating networks structure of self-assembled rod-like lanthanum hydroxide-oxidized multi-walled carbon nanotubes nanocomposite.

In this study, a novel electrochemical sensor based on self-assembled rod-like lanthanum hydroxide-oxidized multi-walled carbon nanotubes (La(OH)3-OxMWCNTs) nanocomposite was developed for sensitive determination of p-nitrophenol (p-NP). The La(OH)3-OxMWCNTs nanocomposite with an interpenetrating networks structure was characterized by field emission electron microscope (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, Raman spectra and X-ray photoelectron spectroscopy (XPS). The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were performed to study the electrochemical behaviors of La(OH)3-OxMWCNTs modified glassy carbon electrode (La(OH)3-OxMWCNTs/GCE). The La(OH)3-OxMWCNTs/GCE was used for sensitive determination of p-NP by CV and linear sweep voltammetry (LSV). Under the optimum conditions, the peak currents of LSV versus the concentrations of p-NP in the range 1.0-30.0 µmol L-1 showed a good linear relationship (R2=0.9971), and the limit of detection (LOD) was calculated to be 0.27 µmol L-1 (signal-to-noise ratio of 3, S/N=3). The recoveries of p-NP in real samples of industrial wastewater and Xiangjiang water at La(OH)3-OxMWCNTs/GCE were in the range of 95.62-110.75% with relative standard deviation (RSD) in the range of 1.65-3.85%. The intra-day and inter-day precisions were estimated to be less than 2.76% (n= 5), indicating that La(OH)3-OxMWCNTs/GCE possessed highly stability. In addition, La(OH)3-OxMWCNTs/GCE sensor showed good anti-interference ability for determination of p-NP in aqueous mixtures containing high concentrations of inorganic and organic interferents, and a decrease of oxidation peak currents by less than 3.57% relative to the initial levels indicated it possessed excellent selectivity. Therefore, La(OH)3-OxMWCNTs/GCE could be used as a fast, selective and sensitive electrochemical sensor platform for the selective determination and quantification of aqueous p-NP.

PtNPs-GNPs-MWCNTs-ß-CD nanocomposite modified glassy carbon electrode for sensitive electrochemical detection of folic acid.

A novel electrochemical sensor, platinum nanoparticles/graphene nanoplatelets/multi-walled carbon nanotubes/ß-cyclodextrin composite (PtNPs-GNPs-MWCNTs-ß-CD) modified carbon glass electrode (GCE), was fabricated and used for the sensitive detection of folic acid (FA). The PtNPs-GNPs-MWCNTs-ß-CD nanocomposite was easily prepared with an ultrasound-assisted assembly method, and it was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behavior of FA at PtNPs-GNPs-MWCNTs-ß-CD/GCE was investigated in detail. Some key experimental parameters such as pH, amount of PtNPs-GNPs-MWCNTs-ß-CD composite, and scan rate were optimized. A good linear relationship (R2 = 0.9942) between peak current of cyclic voltammetry (CV) and FA concentration in the range 0.02-0.50 mmol L-1 was observed at PtNPs-GNPs-MWCNTs-ß-CD/GCE. The detection limit was 0.48 µmol L-1 (signal-to-noise ratio = 3). A recovery of 97.55-102.96% was obtained for the determination of FA in FA pills (containing 0.4 mg FA per pill) at PtNPs-GNPs-MWCNTs-ß-CD/GCE, indicating that the modified electrode possessed relatively high sensitivity and stability for the determination of FA in real samples.

Highly-sensitive and selective determination of bisphenol A in milk samples based on self-assembled graphene nanoplatelets-multiwalled carbon nanotube-chitosan nanostructure.

Graphene nanoplatelets (GNPs), multiwalled carbon nanotube (MWCNTs) and chitosan (CS) were self-assembled by a facile one-step hydrothermal reaction to obtain novel MWCNTs-CS enfolded GNPs (GNPs-MWCNTs-CS) composite. Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), UV-visible (UV-vis) absorption spectroscopy and zeta potential analysis were employed to characterize the morphology, surface composition, interaction, surface charge and stability of the GNPs-MWCNTs-CS composite. The electrochemical behaviors of GNPs-MWCNTs-CS composite modified glassy carbon electrode (GNPs-MWCNTs-CS/GCE) were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The GNPs-MWCNTs-CS/GCE was used for fast and high sensitive determination of bisphenol A (BPA) by differential pulse voltammetry (DPV). Under the optimum conditions, the calibration curve obtained is linear for the current versus the BPA concentration in the range 0.1-100 µM with a detection limit of 0.05 nM (signal-to-noise ratio of 3, S/N = 3). The between-sensor reproducibility was 1.29% (n = 6) for 0.04 mM BPA. The proposed GNPs-MWCNTs-CS/GCE based sensor showed high resistance to interference, good repeatability and excellent reproducibility. Trace BPA in milk samples could also be reliably determined.

A novel electrochemical sensor based on self-assembled platinum nanochains - Multi-walled carbon nanotubes-graphene nanoparticles composite for simultaneous determination of dopamine and ascorbic acid.

In this study, platinum nanochains (PtNCs), multi-walled carbon nanotubes (MWCNTs) and graphene nanoparticles (GNPs) were assembled together to form a novel nanocomposite by a facile ultrasonic-assisted blending process. The PtNCs-MWCNTs-GNPs nanocomposite was characterized by high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The nanocomposite was used for the modification of glass carbon electrode (GCE) and simultaneous determination of dopamine (DA) and ascorbic acid (AA) by differential pulse voltammetry (DPV) and cycle voltammetry (CV). Under the optimum conditions, the calibration curves obtained are linear for the currents versus DA and AA concentrations over the range 2.00-50.0 µM and 100-1200 µM, respectively. And the detection limits for DA and AA are 0.500 µM and 10.0 µM, respectively. The detection and quantitative analysis of DA and AA in human serum and vitamin C tablets on PtNCs-MWCNTs-GNPs/GCE gave the recoveries of 104-110% and 101-108% with relative standard deviations (RSD) of 4.36-7.48% and 0.620-2.90%, respectively. The proposed PtNCs-MWCNTs-GNPs composite could provide a new platform for the routine analysis of DA and AA in terms of its good anti-interference ability, excellent reproducibility and repeatability, and feasibility of use.