Identification of Oxidation Products of (−)-Epigallocatechin Gallate and (−)-Epigallocatechin with H<sub>2</sub>O<sub>2</sub>

Zhu, Nanqun; Huang, Tzu‐Chi; Yu, Younong; LaVoie, Edmond J.; Yang, Chung S.; Ho, Chi‐Tang

doi:10.1021/jf991188c

Cited by 63 publications

(38 citation statements)

References 13 publications

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“…10,12 The higher the pH value of the medium, the greater was the degradation of GTEs. There has been no study on the oxidative decomposition of GTEs in tea drinks except for that of Zhu et al, 14 who isolated and identified three oxidative products when EGCG and EGC interacted with H 2 O 2 . It remains unknown what oxidative products are present in canned and bottled tea drinks.…”

Section: Discussionmentioning

confidence: 99%

Epimerisation of tea polyphenols in tea drinks

Leung

Huang

et al. 2003

J Sci Food Agric

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Manchón N., Mateo-Vivaracho L., D'Arrigo M., García-Lafuente A., Guillamón E., Villares A., Rostagno M.A. (2013): Distribution patterns of polyphenols and alkaloids in instant coffee, soft and energy drinks, and tea. Czech J. Food Sci., 31: 483-500. A previously developed method of HPLC-DAD-Fl has been used for the determination of phytochemical profiles in different types of drinks: instant coffee, soft drinks, energy drinks, and different types of tea (green, white, black, and red tea). Using data on the concentrations of 20 main phytochemicals (phenolic acids, flavan-3-ols, flavonols, flavones, and alkaloids) it was possible to identify most of the sample types. Chlorogenic and caffeic acids and caffeine are the main target compounds in instant coffee; in soft and energy drinks, only caffeine was found. Tea has a more complex phytochemical composition. Unfermented tea is mainly composed of flavan-3-ols and alkaloids, with a high caffeine concentration. Black tea is composed of alkaloids and low levels of flavan-3-ols, which are affected by oxidative reactions during the fermentation. Flavonols are present in lower concentrations in all kinds of teas. The identified phytochemical distribution patterns were used to correctly differentiate instant coffee, soft drinks, energy drinks, unfermented tea and fermented tea (within fermented tea, black tea from red tea can also be differentiated).

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Section: Discussionmentioning

confidence: 99%

Epimerisation of tea polyphenols in tea drinks

Leung

Huang

et al. 2003

J Sci Food Agric

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“…An alternative approach, using a model oxidation system, had thus been developed for the study of polyphenolic compounds. For example, oxidation in model systems has been carried out both chemically by using ferrous sulphate (Oszmianski et al 1996) or hydrogen peroxide (Zhu et al 2000) and enzymatically with polyphenoloxidase (Guyot et al 1996). But until now there are no reports on the comparative studies on the polyphenol extracts from green tea, black tea and chemical oxidation products of green tea extracts.…”

Section: Introductionmentioning

confidence: 99%

Comparative studies on the physicochemical and antioxidant properties of different tea extracts

Chen

2011

J Food Sci Technol

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Tea is one of the most popular drinks next to water. Tea polyphenol is one of the main bioactive constituents of tea with health functions. In order to find the most bioactive tea polyphynols, polyphenol extracts from green tea, black tea and chemical oxidation products of green tea extracts were comparatively studied on the physicochemical and antioxidant properties. Results showed physicochemical and antioxidant properties of polyphenol extracts changed greatly after the chemical oxidation. Hydrogen peroxide induced oxidation products (HOP) possessed the highest antioxidant ability among the four tea polyphenol extracts. Thirteen phenolic compounds and one alkaloid in HOP were identified by reversed phase high-performance liquid chromatography coupled to diode array detection and electrospray ionization mass spectrometry (RP-HPLC-DAD-ESI-MS). Hydrogen peroxide induced oxidation of tea polyphenol extracts could improve the antioxidant activity and could be used to produce antioxidants for food industry.

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“…Conversely, GTPP and EGCG induce cytotoxicity and apoptosis in many types of tumor cells Roy et al, 2003). The EGCGinduced apoptosis has been reported to be associated with oxidative stress imposed on tumor cells, especially by H 2 O 2 (Long et al, 1999;Yang et al, 2000;Zhu et al, 2000). EGCGinduced production of H 2 O 2 was recently observed under in vitro conditions with or without the presence of cells (Long et al, 1999;Hong et al, 2002).…”

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confidence: 99%

“…The ability of these compounds to scavenge reactive oxygen species (ROS) such as hydrogen peroxide (H 2 O 2 ) and superoxide radicals depends on their phenolic chemical structures (Wei et al, 1999;Zhu et al, 2000). GTPP, especially EGCG, may help to protect various cells from chemical or physical damage that leads to carcinogenesis (Wei et al, 1999;Tanaka, 2000;Katiyar and Elmets, 2001;Chen et al, 2002;Lee et al, 2003).…”

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confidence: 99%

Roles of Catalase and Hydrogen Peroxide in Green Tea Polyphenol-Induced Chemopreventive Effects

Yamamoto¹,

Lewis²,

Wataha³

et al. 2003

J Pharmacol Exp Ther

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The green tea polyphenol (Ϫ)-epigallocatechin-3-gallate (EGCG) possesses promising anticancer potential. Although in vivo studies unveiled the metabolic routes and pharmacokinetics of EGCG and showed no adverse effects, in vitro studies at high concentrations demonstrated oxidative stress. EGCG causes differential oxidative environments in tumor versus normal epithelial cells, but the roles that EGCG, hydrogen peroxide (H 2 O 2 ), and intracellular catalase play in the epithelial system are largely unknown. The current study employed enzyme activity assays, reactive oxygen species quantification, and immunoblotting to investigate whether EGCG-induced differential effects correlate with levels of key antioxidant enzymes and H 2 O 2 . It was found that normal human keratinocytes with high catalase activity are least susceptible to H 2 O 2 , whereas H 2 O 2 caused significant cytotoxicity in oral carcinoma cell lines. However, the EGCG-induced differential effects could not be duplicated by H 2 O 2 alone. The addition of exogenous catalase failed to completely prevent the EGCG-induced cytotoxicity and rescue the EGCG-induced growth arrest in the tumor cells. The antioxidant N-acetyl-L-cysteine rescued the tumor cells from H 2 O 2 -induced damage only, but not from EGCGinduced mitochondrial damage. Finally, alterations in catalase or superoxide dismutase activities were not observed upon EGCG exposure. In conclusion, although endogenous catalase may play a role in response to H 2 O 2 -induced cytotoxicity, the EGCG-induced cytotoxic effects on tumor cells mainly result from sources other than H 2 O 2 .

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Identification of Oxidation Products of (−)-Epigallocatechin Gallate and (−)-Epigallocatechin with H₂O₂

Cited by 63 publications

References 13 publications

Epimerisation of tea polyphenols in tea drinks

Epimerisation of tea polyphenols in tea drinks

Comparative studies on the physicochemical and antioxidant properties of different tea extracts

Roles of Catalase and Hydrogen Peroxide in Green Tea Polyphenol-Induced Chemopreventive Effects

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Identification of Oxidation Products of (−)-Epigallocatechin Gallate and (−)-Epigallocatechin with H2O2

Cited by 63 publications

References 13 publications

Epimerisation of tea polyphenols in tea drinks

Epimerisation of tea polyphenols in tea drinks

Comparative studies on the physicochemical and antioxidant properties of different tea extracts

Roles of Catalase and Hydrogen Peroxide in Green Tea Polyphenol-Induced Chemopreventive Effects

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Identification of Oxidation Products of (−)-Epigallocatechin Gallate and (−)-Epigallocatechin with H₂O₂