Research Database

Author: Anna Marchese and Erika Coppo and Anatoly P. Sobolev and Daniela Rossi and Luisa Mannina and Maria Daglia

The antistaphylococcal activity as well as the metabolic profiling and polyphenols content of green tea (Camellia sinensis) before and after in vitro simulated gastric, duodenal and gastroduodenal digestion were investigated. Gastric and duodenal digested samples showed antistaphylococcal activity, whereas gastroduodenal digested samples did not show any antibacterial activity. Metabolite analysis, carried out using an explorative untargeted NMR-based approach and a RP-HPLC-PAD-ESI–MSn method, showed that green tea polyphenols are stable under gastric conditions. Duodenal digested sample maintained the antibacterial activity, even if some polyphenols are widely degraded. Epicatechin 3-gallate, under duodenal digestive conditions, is hydrolyzed to produce epicatechin, whereas epigallocatechin 3-gallate reacts with digestive enzymes and a galloyl-high molecular weight derivative is produced. Gastroduodenal digestion results in degradation of polyphenols, especially gallocatechins, considered the main responsible for the antibacterial activity. These results explain the loss of activity of gastroduodenal digested samples and why in vivo green tea has neither protective nor therapeutic effects against intestinal and systemic bacterial infections.

 

 

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Author: Yang-Hee Hong and Eun Young Jung and Dong Ouk Noh and Hyung Joo Suh

Background Green tea contains numerous polyphenols, which have health-promoting effects. The purpose of this study was to evaluate the effect of tannase-converted green tea extract (TGE) formulation on the physical stability and activities of skin-related enzymes. Methods Physical stability was evaluated by measuring the pH, precipitation, and colors at 25 ± 2°C/ambient humidity and at 40 ± 2°C/70% ± 5% relative humidity for 4 months. Activities of collagenase, elastase, and tyrosinase as skin-related enzymes were assessed on TGE formulation. Results The concentrations of epigallocatechin-3-gallate and epicatechin-3-gallate in green tea extract were greatly decreased to the extent of negligible level when treated with tannase. The formulation containing 5% tannase-converted green tea extract showed relatively stable pH, precipitation, and color features for 16 weeks. When TGE was added to the formulation, there was a significant increase in the inhibition of elastase and tyrosinase activities (p < 0.05) compared with the formulation containing 5% normal green tea extract. Conclusion The TGE could be used in cosmetics as skin antiwrinkling or depigmenting agent.

 

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Author: Mara Mirasoli and Roberto Gotti and Massimo Di Fusco and Alberto Leoni and Carolina Colliva and Aldo Roda

Electronic nose and capillary electrophoresis were applied in quality control of green tea samples subjected to long-term storage. Twelve representative green teas were considered, available as an “aged” (tea leaves stored during a long-term period of two years) and/or “not aged” (fresh products) samples. Their infusions were analyzed by an electronic nose, equipped with an array of six metal oxide semiconductor (MOS) sensors to obtain olfactive fingerprints of the volatile compounds in the infusions headspace. Upon training and chemometric analysis of acquired data (linear discriminant analysis), the electronic nose was found to be able in correctly classifying unknown samples as “aged” or “not aged”. Concomitantly, the infusion samples were analyzed by Cyclodextrin-modified Micellar Electrokinetic Chromatography (CD-MEKC) for determination of catechins. The analysis of seven most represented catechins and the methylxanthines theobromine and caffeine revealed a general loss of the polyphenols in each of the considered aged samples (up to 45%, w/w). In addition, the applied enantioselective method based on (2-hydroxypropyl)-β-cyclodextrin (HP-βCD) as chiral selector, was exploited for the estimation of (+)-Gallocatechin in the presence of (−)-Gallocatechin; the latter, as the non-native enantiomer, can be associated to the epimerisation of (−)-Epigallocatechin and was assumed as a marker occurring in case of uncorrected storage conditions of tea leaves. Interestingly, it was observed that epimerization did not significantly occur during aging. The application of CD-MEKC and electronic nose allowed for a fast characterization of green teas taking into account that the aroma is a decisive parameter for the acceptance of the product, whereas the catechins content is associated to the biological value.

 

 

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Author: Kayleigh A. Clarke and Tristan P. Dew and Rachel E.B. Watson and Mark D. Farrar and Susan Bennett and Anna Nicolaou and Lesley E. Rhodes and Gary Williamson

The simultaneous analysis of free-form and conjugated flavonoids in the same sample is difficult but necessary to properly estimate their bioavailability. A method was developed to optimise the extraction of both free and conjugated forms of catechins and metabolites in a biological sample following the consumption of green tea. A double-blind randomised controlled trial was performed in which 26 volunteers consumed daily green tea and vitamin C supplements and 24 consumed a placebo for 3 months. Urine was collected for 24 h at 4 separate time points (pre- and post-consumption) to confirm compliance to the supplementation and to distinguish between placebo and supplementation consumption. The urine was assessed for both free and conjugated metabolites of green tea using LC–MS2 analysis, after a combination extraction method, which involved an ethyl acetate extraction followed by an acetonitrile protein precipitation. The combination method resulted in a good recovery of EC-O-sulphate (91 ± 7%), EGC-O-glucuronide (94 ± 6%), EC (95 ± 6%), EGC (111 ± 5%) and ethyl gallate (74 ± 3%). A potential total of 55 catechin metabolites were investigated, and of these, 26 conjugated (with methyl, glucuronide or sulphate groups) and 3 free-form (unconjugated) compounds were identified in urine following green tea consumption. The majority of EC and EGC conjugates significantly increased post-consumption of green tea in comparison to baseline (pre-supplementation) samples. The conjugated metabolites associated with the highest peak areas were O-methyl-EC-O-sulphate and the valerolactones M6/M6′-O-sulphate. In line with previous studies, EC and EGC were only identified as conjugated derivatives, and EGCG and ECG were not found as mono-conjugated or free-forms. In summary, the method reported here provides a good recovery of catechin compounds and is appropriate for use in the assessment of flavonoid bioavailability, particularly for biological tissues that may contain endogenous deconjugating enzymes.

 

 

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Author: A.J. Pham⁎ and J.B. Williams and A.C. Tolentino and J.L. Silva and M.W. Schilling

 

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Author: A.J. Pham and J.B. Williams and S. Kin and Y.L. Xiong and M.W. Schilling

 

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Author: Prakitpunthu Tomtitchong and Jean E. Crabtree

Introduction: Epidemiological studies suggest epigallocatechin-3-gallate (EGCG), a natural product from green tea, may have a role in prevention of gastric atrophy and gastric cancer in Asian populations. Anyway, the diversity of results from in vivo studies was observed. Our group reported that EGCG inhibits H. pylori-induced upregulation of COX-2, EGF- related ligand and ADAMs transcripts, ERK phosphorylation and IL-8 activation in gastric and non-gastric epithelial cells. But we have simultaneously observed that EGCG can be a stimulator in some conditions. Recently, an EGCG specific receptor has been identified which is the 67 kDa laminin receptor (LR). We postulate that varying levels of the EGCG receptor, the 67 kDa LR, on different cell lines may modify the in vitro results determining the inhibitory effects of EGCG on cell signaling pathways. Methods: MKN28, MGEC, L5F11 and A431 epithelial cells were incubated with MLuC5 mouse monoclonal IgM before incuba- tion with TRITC-conjugated goat anti-mouse expression of the EGCG receptor. The 67 kDa laminin receptor (LR) or EGCG receptor was evident by immunofluorescence. Expression levels of EGCG receptor were compared with the different responses to EGCG among the four cell lines. Results: Strong expression of the EGCG receptor was evident on MKN28 cells but reduced levels were observed on L5F11 and A431 cells. MGEC cells show no expression of 67 kDa LR. Conclusions: Varying levels of the laminin or EGCG receptor may explain the different responses of the cell lines to EGCG and might explain variation of a role EGCG in prevention of H. pylori-induced gastric carcinogenesis.

 

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Author: S. Yamada and S. Misaka and K. Tanabe and A. Osano and K. Takeuchi and J.P. Werba and H. Watanabe

Background and purpose: Green tea has been reported to have various health benefits including cancer prevention and antiox- idative effect. Catechins, the main flavonoids in green tea, are considered to be potential components of these effects. Recently, a case report suggested that the consumption of catechin-rich green tea is associated with simvastatin intolerance. The present study aimed to evaluate the effect of catechin-rich green tea consumption on the pharmacokinetics of simvastatin lactone (SIM) and simvas- tatin acid (SVA), which are a prodrug and an active metabolite of simvastatin, respectively. Methods: In an open-label, two-way crossover study with 14 days washout, a single oral dose of 10mg SIM was administered to 12 healthy Japanese male volunteers (23–26 years old; body weight, 65.1±2.4 kg) after drinking of green tea (700mL/day, total catechinsof1080mg)orwater for2weeks. Bloodsampleswerecol- lected up to 24h after the administration. Plasma concentrations of SIM and SVA were determined using LC/MS/MS. Pharmacokinetic parameters were estimated by noncompartmental analysis. Results and discussion: Chronic consumption of catechin- rich green tea led to increases in the area under the plasma concentration-time curve (AUC0–∞) andmaximum concentration (Cmax) of SIM by 1.6- and 1.3-folds, respectively, as compared to water. No change was observed in the elimination half-life of SIM between green tea andwater, indicating that catechinsmainlymay inhibit SIMmetabolism in the intestine. In addition, green tea con- sumption significantly increased AUC0–∞ and Cmax of SVA by 1.5 and 1.6-folds, respectively, suggesting that green teamay affect not only the pharmacokinetics, but also the pharmacodynamics of SVA. Conclusion: The chronic consumption of catechin-rich green tea may cause the clinically relevant interaction with simvastatin.

 

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Author: Saeed Masoum and Mohsen Behpour and Fatemeh Azimi and Mohammad Hassan Motaghedifard

Differential pulse voltammetry technique assisted by chemometric methods such as multivariate curve resolution-alternating least squares (MCR-ALS) has been proposed as a valuable approach for (+)-catechin determination in the presence of gallic acid at the surface of multiwalled carbon nanotube paste electrode. Central composite design and response surface methodology were used to optimize the influencing parameters. To determine (+)-catechin in the presence of unexpected electroactive interference with a very high degree of overlapping, second-order electrochemical data were generated by changing the pulse height as an instrumental parameter. After potential shift correction, MCR-ALS results show that second-order calibration could be applied with great success for electroanalytical determination of highly overlapped electroactive species. The linear least-squares calibration curve based on the area under concentration profile was provided over the range of 0.10–2.69 μM for (+)-catechin, whereas detection limit was found to be 0.017 μM. Also in this study, the effect of rotational ambiguity associated with a particular MCR solution under a set of constraints was investigated.

 

 

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Author: Sofia Benyahya and Chahinez Aouf and Sylvain Caillol and Bernard Boutevin and Jean Pierre Pascault and Hélène Fulcrand

Phenolic extract from the green tea leaves was used for the production of thermoset epoxy resins. The commercial green tea extract (GTE) was functionalized by the reaction with epichlorohydrin in the presence of phase transfer catalyst. The glycidyl ether derivative of the green tea extract (GEGTE) obtained with a good yield was cured in epoxy polymer with isophorone diamine (IPD) and the resulting network was compared to catechin-IPD and diglycidyl ether of bisphenol A (DGEBA-IPD) systems. The thermal and mechanical analyses of this bio-based epoxy polymer showed its high reactivity associated with a high crosslinking density (Tg: 140–190 °C), a high thermal resistance and interesting mechanical properties.

 

 

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