Time filter

Source Type

Zhang L.,Henan University | Zhang L.,Key Laboratory of Natural Products and Immunology | Bai B.,Henan University | Liu X.,Henan University | And 5 more authors.
Food Chemistry | Year: 2011

The inhibitory activities of crude extracts and purified constituents from the fresh tuberous rhizomes of Chinese Yam (Dioscorea opposita Thunb.), which is commonly called Huai Shan Yao in Chinese, were evaluated against yeast α-glucosidase in order to search for the active principals for treatment of diabetes. Bioassay-guiding isolation gave four compounds: trans-N-p-coumaroyltyramine (1) (IC50 = 0.40 μM), 1,7-bis(4-hydroxyphenyl)heptane-3,5-diol (2) (IC50 = 0.38 mM), 6-hydroxy-2,4,7-trimethoxyphenanthrene (3) (IC50 = 0.77 mM) as α-glucosidase inhibitors, and cis-N-p-coumaroyltyramine (4), an isomer of compound 1, which showed no inhibitory activity against α-glucosidase. Furthermore, the separation and purification of compound 3 from Chinese Yam (Huai Shan Yao) was conducted by high-speed counter-current chromatography (HSCCC) using hexane-ethyl acetate-methanol-water (1:1:1:1, v/v/v/v). Compound 1, 2 and 4 were isolated from or detected in the Dioscoreaceae family for the first time. © 2010 Elsevier Ltd. All rights reserved.

Liu X.,Henan University | Feng H.,Henan University | Zhao R.,Henan University | Wang Y.,Henan University | And 2 more authors.
Biosensors and Bioelectronics | Year: 2012

The direct electrochemistry of horseradish peroxidase (HRP) on a novel sensing platform modified glassy carbon electrode (GCE) has been achieved. This sensing platform consists of Nafion, hydrophilic room-temperature ionic liquid (RTIL) and Au nanoparticles dotted titanate nanotubes (GNPs-TNTs). The composite of RTIL and GNPs-TNTs was immobilized on the electrode surface through the gelation of a small amount of HRP aqueous solution. The composite was characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and infrared spectroscopy (IR). UV-Vis and IR spectroscopy demonstrated that HRP in the composite could retain its native secondary structure and biochemical activity. The HRP-immobilized electrode was investigated by cyclic voltammetry and chronoamperometry. The results from both techniques showed that the direct electron transfer between the nanocomposite modified electrodes and heme in HRP could be realized. The biosensor responded to H 2O 2 in the linear range from 5×10 -6 to 1×10 -3molL -1 with a detection limit of 2.1×10 -6molL -1 (based on the S/N=3). © 2011 Elsevier B.V..

Liu X.,Henan University | Zhang J.,Henan University | Yan R.,Henan University | Zhang Q.,Henan University | Liu X.,Key Laboratory of Natural Products and Immunology
Biosensors and Bioelectronics | Year: 2014

A novel nanocomposite consisting of graphene nanoplatelets (GNPs) and titanate nanotubes (TNTs) have been synthesized successfully utilizing the hydrothermal method. The GNP-TNT composite was characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy. The voltammetric characterization of GNP-TNT composite, pure GNPs and pure TNTs modified horseradish peroxidase (HRP) biosensors were conducted to select the most suitable electrode immobilization material for enzyme biosensors. The GNPs was firstly eliminated owing to its extremely high background charging current, distinct electrochemical interference from its surface functional groups and low signal to noise ratio. Next, the direct electron transfer of HRP on electrode and the catalytic current of HRP towards H2O2 was increased around 45% and 72% respectively on GNP-TNT composite modified electrodes compared with those on pure TNTs modified electrodes. GNP-TNT composite modified HRP biosensor also exhibited superiority over pure TNTs modified HRP biosensor in the analytical performance. The precision and stability study provided additional evidence for the feasibility of using GNP-TNT composite as electrode modification material. © 2013 Elsevier B.V.

Loading Key Laboratory of Natural Products and Immunology collaborators
Loading Key Laboratory of Natural Products and Immunology collaborators