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Mechanism of action of (-)-epigallocatechin-3-gallate:auto-oxidation-dependent activation of extracellular signal-regulated kinase 1/2 in Jurkat cells

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Chinese Journal of Natural Medicines 2014年第9期12卷 654-662页

作者： SONG Shuang HUANG Ye-Wei TIAN Yang WANG Xuan-Jun SHENG Jun College of Life Sciences Jilin University Key Laboratory of Puer Tea Science Ministry of Education Kunming Yunnan Agriculture University

AIM:(-)-Epigallocatechin-3-gallate(EGCG), a major compound of tea polyphenols, exhibited antitumor activity in previous studies. In these studies, EGCG usually inhibits EGFR, and impairs the ERK1/2 phosphorylation in tumor cells. The aim was to clarify the mechanism of ERK1/2 activation induced by EGCG. METHODS: Jurkat and 293 T cells were treated with EGCG in different culture conditions. Western Blotting(WB) was employed to analyze ERK1/2 and MEK phosphorylation. Cetuximab and FR180204 were used to inhibit cell signaling. The stability of EGCG was assessed by HPLC. The concentration of hydrogen peroxide generated by the auto-oxidation of EGCG was determined by photocolorimetric analysis. RESULTS: Activation of ERK1/2 was observed to be both time- and dose-dependent. Stimulation of cell signaling was dependent on MEK activity, but independent of EGFR activity. Unexpectedly, EGCG was depleted within one hour of incubation under traditional culture conditions. auto-oxidation of EGCG generated a high level of hydrogen peroxide in the medium. Addition of catalase and SOD to the acidic medium inhibited the oxidation of EGCG. However, this particular condition also prevented the phosphorylation of ERK1/2. The generation of ROS by hydrogen peroxide may also induce ERK1/2 activation in Jurkat cells. CONCLUSION: ERK1/2 phosphorylation was caused by auto-oxidation of EGCG. Traditional culture conditions were determined to be inappropriate for EGCG research.

关键词： (-)-Epigallocatechin-3-gallate(EGCG) ERK1/2 Hydrogen peroxide auto-oxidation Phosphorylation

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On the Usage of the Faraday Effect as an Authentication Technique for Vegetable Oils

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Journal of Modern Physics 2013年第2期4卷 230-235页

作者： M. I. Abu-Taha M. A. Halasa M. M. Abu-Samreh Physics Department College of Science and Technology Al-Quds University Jerusalem Palestine

In this study we report on the measurements of the Verdet constant for olive and other vegetable oils. Study of samples stored for different periods at different storage conditions showed that each olive oil sample has a Verdet constant value depending on: production year, history of the sample (i.e. storage conditions) and geographical region. Photo and auto oxidations are found to have reverse effects on the value of the measured Verdet constant, on the one hand, photo-oxidation tends to decrease the Verdet constant, but on the other hand auto-oxidation tends to increase it. It is known that oils stored in room light had significantly lower tocopherol, carotenoid, and chlorophyll contents than did the same oils kept in the dark. For other vegetable oil samples, each vegetable oil was found to have a distinct Verdet constant value. Thus it is possible to differentiate vegetable oils making use of their respective Verdet constants. Preliminary results indicated the possibility to detect olive oil adulteration using the Faraday Effect, i.e. the effect could be suggested as a food authentication technique if calibration curves and standard Verdet constants values could be prepared for comparison with those of samples under investigation.

关键词： Olive Oil Oil Content Oil Adulteration Photo-oxidation auto-oxidation Magneto-Optics Food Authentication

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