Antioxidant Chemistry of Green Tea Catechins. New Oxidation Products of (−)-Epigallocatechin Gallate and (−)-Epigallocatechin from Their Reactions with Peroxyl Radicals

Valcic, Susanne; Burr, Jeanne A.; Timmermann, Barbara N.; Liebler, Daniel C.

doi:10.1021/tx000080k

Cited by 150 publications

(98 citation statements)

References 42 publications

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“…Polyphenols have antioxidant, 4,5) anti-inflammatory, 6,7) hypoglycemic, hypolipidemic, 8) depression of hypertension, 9) and other biological properties. Polyphenols are divided into several groups, one of which is represented by flavonoids.…”

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confidence: 99%

Analysis of Green Tea Compounds and Their Stability in Dentifrices of Different pH Levels

Jang

Park

Ahn

et al. 2014

CHEMICAL & PHARMACEUTICAL BULLETIN

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In this study, green tea compounds (flavonoids, alkaloids, and phenolic acids) were analyzed in green tea-containing dentifrices, and their stability at different pH levels was evaluated. The compounds were separated under 0.01% phosphoric acid-acetonitrile gradient conditions and detected by photodiode array detector at 210, 280, 300, 335 nm. Column temperature was set at 20°C based on the results of screening various temperatures. Each compound showed good linearity at optimized wavelength as well as showing good precision and accuracy in dentifrices. Using this method, the stability of compounds was investigated in pH 4, 7, 8, and 10 solutions for 96 h, and in pH 7 and pH 10 solutions for 6 months. The green tea compounds were more stable at low pH levels; purine alkaloids were more stable than flavonoids. In particular, gallocatechin (GC), epigallocatechin (EGC), epigallocatechin gallate (EGCG), gallocatechin gallate (GCG), and myricetin almost disappeared in pH 10 solutions after 96 h. In dentifrices, the compounds were gradually decreased until 6 months in both pH types, while gallic acid was increased because of production of galloyl ester of other green tea compounds. Therefore, it is beneficial to adjust to as low a pH as possible when produce green teacontaining dentifrices.

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confidence: 99%

Analysis of Green Tea Compounds and Their Stability in Dentifrices of Different pH Levels

Jang

Park

Ahn

et al. 2014

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…27 Green tea catechins have been extensively investigated in the last two decades. [28][29][30][31] Also, it is probably the most consumed beverage worldwide. 32 In addition, green tea contains a significant percentage of the purine alkaloid caffeine making it particularly suitable for the examination of our resin-based separation method.…”

Section: Resultsmentioning

confidence: 99%

Application of Phase-Trafficking Methods to Natural Products Research

Araya¹,

Montenegro²,

Mitscher³

et al. 2011

J. Nat. Prod.

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A novel simultaneous phase-trafficking approach using spatially separated solid-supported reagents (SSR) for rapid separation of neutral, basic, and acidic compounds from organic plant extracts with minimum labor is reported. Acidic and basic ion exchange resins were physically separated into individual sacks ("teabags") for trapping basic and acidic compounds respectively, leaving behind in solution neutral components of the natural mixtures. Trapped compounds were then recovered from solid phase by appropriate suspension in acidic or basic solutions. The feasibility of the proposed separation protocol was demonstrated and optimized with an "artificial mixture" of model compounds. In addition, the utility of this methodology was illustrated with the successful separation of the alkaloid skytanthine from Skytanthus acutus Meyen and the main catechins and caffeine from Camellia sinensis L. (Kuntze). This novel approach offers multiple advantages over traditional extraction methods, as it is not labor intensive, makes use of only small quantities of solvents, produces fractions in adequate quantities for biological assays, and can be easily adapted to field conditions for bioprospecting activities.In 1963, R. B. Merrifield revolutionized peptide synthesis by introducing solid-phase reagents. This brilliantly simple idea allowed the use of reagents in excess and simplified purification, leading to higher yields and fast isolation. 1 Subsequent elaboration using combinatorial techniques have led to peptide compound libraries of thousands of compounds. Since then, an impressive number of inventive modifications have been introduced in a wide range of fields in academia and industrial laboratories. [2][3] Particularly, organic chemists have taken advantage of specific interactions between small organic molecules and solid-supported reagents (SSR) to achieve quick purification of desired nonpeptide products applying creative phase-switching strategies. 4 Furthermore, the isolation process using solid-phase protocols only involves simple operations of filtration and solvent removal that are suitable for automation and high throughput applications and has found particular value in combinatorial chemistry laboratories. 5 Despite the multiple advantages of SSR for isolation of small synthetic organic molecules, this method has yet to find application in resolving natural product extracts. Ion-exchange resins have long been used for purification of particular natural products (i.e. quinine 6-7 ) at a scale only occasionally used in fractionation schemes. Few examples of applications to natural products research These methods require either a substantial investment or lengthy and tedious protocols, preventing their implementation, especially in the remote regions of current bioprospecting interest. Consequently, the need for applications that can generate samples conveniently with suitable quality for initial bioassay is of great current interest. Such a method should not only increase the relative concentration of p...

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“…Many investigations have outlined the potent antioxidant proprieties of tea and GTPs (Valcic et al, 2000;Gramza and Korczak, 2005;Koutelidakis et al, 2009). As expected from the variability in polyphenol concentrations, the antioxidant capacity of green tea extracts strongly depends on the extraction processes used.…”

Section: Antioxidant Activitymentioning

confidence: 99%

Microwave‐assisted water extraction of green tea polyphenols

Nkhili

Tomao

Hajji

et al. 2009

Phytochemical Analysis

124

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ABSTRACT:Introduction -Green tea, a popular drink with benefi cial health properties, is a rich source of specifi c fl avanols (polyphenols). There is a special interest in the water extraction of green tea polyphenols since the composition of the corresponding extracts is expected to refl ect the one of green tea infusions consumed worldwide. Objective -To develop a microwave-assisted water extraction (MWE) of green tea polyphenols. Methodology -MWE of green tea polyphenols has been investigated as an alternative to water extraction under conventional heating (CWE). The experimental conditions were selected after consideration of both temperature and extraction time. Conclusion -MWE appears more effi cient than CWE at both 80 and 100°C, particularly for the extraction of fl avanols and hydroxycinnamic acids. Although MWE at 100°C typically aff ords higher yields in total phenols, MWE at 80°C appears more convenient for the extraction of the green tea-specifi c and chemically sensitive fl avanols.

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Antioxidant Chemistry of Green Tea Catechins. New Oxidation Products of (−)-Epigallocatechin Gallate and (−)-Epigallocatechin from Their Reactions with Peroxyl Radicals

Cited by 150 publications

References 42 publications

Analysis of Green Tea Compounds and Their Stability in Dentifrices of Different pH Levels

Analysis of Green Tea Compounds and Their Stability in Dentifrices of Different pH Levels

Application of Phase-Trafficking Methods to Natural Products Research

Microwave‐assisted water extraction of green tea polyphenols

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