Bioavailability and catabolism of green tea flavan-3-ols in humans

ObjectiveThe aim of this study was to investigate green tea flavan-3-ol catabolism and plasma pharmacokinetic and urinary excretion by high-performance liquid chromatography with tandem mass spectrometry to evaluate their absolute bioavailability by taking into account all known and some unknown catabolites deriving from their interaction with the gastrointestinal tract and its host microflora.MethodsA feeding study was carried out in 20 healthy human volunteers who ingested 400 mL of a ready-to-drink green tea containing approximately 400 μmol of flavan-3-ols. Urine and plasma were collected for 4 and 24 h, respectively, and 39 relevant catabolites were identified in these biological fluids by tandem mass spectrometry.ResultsIn biological fluids, 39 relevant flavan-3-ol catabolites were identified. In plasma, (?)-epigallocatechin-3-gallate was the only unmetabolized compound and the highest in absolute concentration compared with (?)-epigallocatechin and (?)-epicatechin conjugates. Colonic microflora-derived polyhydroxyphenyl-γ-valerolactones were by far the main urinary catabolites, averaging 10 times greater concentratin than flavan-3-ol conjugates. The calculated bioavailability was equal to 39% and it is interesting to notice the great variability in urinary excretion of colonic metabolites among participants, probably related to differences in their own colonic microflora.ConclusionThis study demonstrates that green tea catechins are more bioavailable than previously observed when colonic ring fission metabolites are taken into consideration. Regular consumption of ready-to-drink green tea containing flavan-3-ols allows a non-marginal exposure of the human body to these catabolites, somehow justifying the numerous beneficial actions described as linked to green tea intake.     

Dietary fiber and flavan-3-ols in shortbread biscuits enriched with barley flours co-products

The coarse fraction obtained by air classification of barley flour, rich in dietary fiber and flavan-3-ols, was utilized to develop functional biscuits. The flavan-3-ol content, antioxidant activity and oxidative stability of biscuits were measured during storage under retail conditions for 1 year. The replacement of 60% (w/w) refined wheat flour with barley coarse fraction increased the ash, fiber and flavan-3-ol contents significantly. Biscuit samples enriched with barley coarse fraction had a significantly higher amount of fiber compared with the control sample (six times higher). The β-glucan content in enriched samples was 15 times higher than control samples. The flavan-3-ol loss in biscuits after baking was about 67%. The initial content of flavan-3-ols increased from 0.6 to 4.3 mg/100 g in biscuits formulated with barley coarse fraction and showed improved antioxidant properties. Lipid oxidation increased during the shelf-life; the enriched biscuit showed the higher lipid oxidation status, but the level reached during the shelf-life was lower than the limit of acceptance reported for bakery products and, for this reason, does not compromise the safety.     

Isolation of green coffee chlorogenic acids using activated carbon

Chlorogenic acids, which are interesting natural antioxidants widespread in the plant kingdom, were extracted and purified from Mexican green coffee beans (Coffea arabica) using different methods. The final objective was to find an easy way to extract high-value molecules from a complex mixture, avoiding as much as possible the use of toxic solvents. Three extraction methods (hot water at 80 °C, aqueous methanol 70% (v/v), and aqueous isopropanol 60% (v/v)) were tested in combination with two isolating methods (activated carbon, different solvents). The extracted amounts of chlorogenic acids with the six treatments (4.67–5.87% dry basis) presented no significant differences. The one using hot water for extraction and of activated carbon for isolation, was the simplest and the most environmentally friendly. Thus it can be used as a previous step to obtain from green coffee a mixture rich in chlorogenic acids which can be further fractionated to purify a specific chlorogenic acid (i.e. in this work, 5-O-caffeoyl quinic acid using a silica gel column). Chlorogenic acids can be used as natural antioxidants in food or non-food products. To the best of our knowledge, activated carbon has not been used to isolate chlorogenic acids from green coffee.     

Antioxidant activity and polyphenol content of green tea flavan-3-ols and oligomeric proanthocyanidins

The antioxidant activity and total phenolics content (TPC) of freshly prepared green tea extract (GTE) as affected by time, temperature and stirring were determined using the ferric reducing antioxidant power (FRAP) and Folin–Ciocalteu assays, respectively. Acetone–water fractions of GTE containing flavan-3-ols and oligomeric proanthocyanidins were evaluated at concentrations between 25 and 500 µg/ml. Increasing the extraction time from 3 min to 10 min resulted in a significant increase in both the FRAP values and TPC. Increasing the extraction time from 10 min to 30 min was without any significant effects on both FRAP and TPC values. Moreover, the FRAP values were correlated with the TPC. GTE fractions had widely different FRAP values that were well correlated with the TPC of the fraction. It was concluded that brewing conditions such as extraction temperature, period of extraction, ratio of tea leaves to extracting water, and stirring are important factors for determining the FRAP values and TPC in GTE. These factors should be taken into consideration during preparation for nutritional benefits during usual consumption of this beverage. Elevated FRAP and TPC values corresponded to those GTE fractions with a higher amount of phenolic compounds, which have stronger antioxidant activities.     

Dietary flavan-3-ols intake and metabolic syndrome risk in Korean adults

Flavan-3-ols are a subclass of flavonoids found in a variety of foods including teas. The effects of flavan-3-ols on the risk of metabolic syndrome (MetS) have been investigated, generally focusing on tea catechins or individual flavan-3-ol rich foods, but there is little information on dietary flavan-3-ols intake and risk of MetS in population-based studies. In this cross-sectional study, we examined the association between dietary flavan-3-ols intake and the risk of MetS in Korean adults. Subjects comprised 1,827 men and 2,918 women aged 20-69 years whose data was included in the 2008 Korean National Health and Nutrition Examination Survey. This survey was conducted between January 2008 and December 2008. Total flavan-3-ols intakes were calculated from 24-hour dietary recalls using a flavonoids database. Thirty percent of the male subjects and 24% of the female subjects were reported as having MetS. In the female subjects, flavan3-ols intake was inversely associated with the risk of MetS after adjusting for potential confounders (5th vs. 1st quintile, OR = 0.64, 95% CI = 0.45-0.91, P for trend = 0.384). The main food source of flavan-3-ols was green tea followed by apples and grapes. Among MetS components, flavan3-ols intake was inversely associated with the risk of high blood pressure after adjusting for potential confounders (5th vs. 1st quintile, OR = 0.64, 95% CI = 0.45-0.90, P for trend = 0.005). No significant association between flavan-3-ols intake and risk of MetS was found in the male subjects. After stratified analysis by obesity (BMI ≥ 25 or BMI < 25), however, flavan3-ols intake was inversely related to the risk of hypertension in non-obese men. These results suggest that dietary flavan-3-ols intake may have beneficial effects on MetS risk by reducing the risk of hypertension. The effects of flavan-3-ols intake dependent on obesity need further investigation.     

Antioxidant activity and polyphenol content of green tea flavan-3-ols and oligomeric proanthocyanidins

The antioxidant activity and total phenolics content (TPC) of freshly prepared green tea extract (GTE) as affected by time, temperature and stirring were determined using the ferric reducing antioxidant power (FRAP) and Folin-Ciocalteu assays, respectively. Acetone-water fractions of GTE containing flavan-3-ols and oligomeric proanthocyanidins were evaluated at concentrations between 25 and 500 μg/ml. Increasing the extraction time from 3 min to 10 min resulted in a significant increase in both the FRAP values and TPC. Increasing the extraction time from 10 min to 30 min was without any significant effects on both FRAP and TPC values. Moreover, the FRAP values were correlated with the TPC. GTE fractions had widely different FRAP values that were well correlated with the TPC of the fraction. It was concluded that brewing conditions such as extraction temperature, period of extraction, ratio of tea leaves to extracting water, and stirring are important factors for determining the FRAP values and TPC in GTE. These factors should be taken into consideration during preparation for nutritional benefits during usual consumption of this beverage. Elevated FRAP and TPC values corresponded to those GTE fractions with a higher amount of phenolic compounds, which have stronger antioxidant activities.     

Do flavan-3-ols from green tea reach the human brain?

Abstract

Following acute ingestion of green tea by six human subjects, HPLC-MS 2 analysis revealed that flavan-3-ol methyl, glucuronide and sulfate metabolites appeared in the bloodstream but did not pass through the blood–cerebrospinal fluid barrier. These observations emphasize the discrepancies between in vitro and in vivo evidence on the neuroprotective role of these compounds. If, as has been proposed, green tea exerts neuroprotective effects, this finding indicates that the active components are not flavan-3-ols or their metabolites. Alternatively, a systemic action may be hypothesised whereby dietary flavan-3-ols up-regulate antioxidant defences and/or reduce inflammation, the benefit of which may be effective throughout the body.     

Nongallated compared with gallated flavan-3-ols in green and black tea are more bioavailable

Green tea and black tea (BT) contain gallated [(-)-epigallocatechin-3-gallate (EGCG), (-)-epicatechin-3-gallate] and nongallated [(-)-epicatechin, (-)-epigallocatechin (EGC)] tea polyphenols (PP). During BT production, PP undergo oxidation and form larger polymers such as theaflavins (THE) and thearubigins, which contribute to the health benefit of BT. This article gives an overview of the role of chemical characteristics and endogenous metabolism of tea PP and their bioavailability in humans and describes attempts to increase their bioavailability. At pH close to neutral, EGCG and EGC form homo- and heterodimers generating hydrogen peroxide. To confirm the pH instability of EGCG, EGC, and THE in cell culture medium, their antiproliferative activity was determined in the presence and absence of catalase. The antiproliferative activity in LNCaP prostate cancer cells was decreased when incubated with catalase prior to EGCG, EGC, and THE treatment. In addition, new findings demonstrated that the formation of methyl-EGC increased the stability at neutral pH compared with EGC. Approaches to increase the bioavailability of flavan-3-ols are reviewed, which include the administration of tea in combination with fruit juices, coadministration with piperine, and peracetylation of EGCG. Future intervention studies will need to focus on the bioactivity not only of green tea and BT PP but also of their metabolites and biotransformation products.     

Sensitization to green coffee beans and work-related allergic symptoms in coffee workers

Background Occupational respiratory allergy to green coffee beans (GCB) and to castor beans (CB) was studied in 112 workers in a modern coffee manufacturing plant of Trieste (Italy), where the process is completely automatic, the environmental conditions are good and where exposure to CB can be considered absent because since 1970, only new sacks have been used for coffee transportation. Methods All subjects were interviewed by a trained doctor using a questionnaire to investigate allergic symptoms and predisposing factors. Sensitization to GCB and to common allergens (pollens, molds, house dust mites) were evaluated by the skin-prick test. The serum of subjects with a positive skin-prick test to CGB or who had symptoms at work was tested for specific IgE (RAST) for GCB and CB. Lung function was evaluated by a Ponigraph spirometer. Results Sensitization to GCB was found in 25.8% of green coffee workers (31 cases), in 2.7% of roasted coffee workers (37 cases) and in 4.5% of the clerks (44 cases), p < 0.01. The evaluation of IgE specific for CB gave positive results only in 3 of 10 subjects sensitized to GCB. A total of 20% of GCB workers (6 cases) complained of work-related respiratory symptoms (asthma and/or rhinitis) compared with only one subject in the roasted coffee group and one in the control group (p < 0.01). Asthma was reported by 2/31 of the green coffee workers and by 1/44 of roasted coffee workers. Conclusions There was a significant correlation between sensitization to GCB and work related symptoms (p < 0.01), common allergic symptoms (p < 0.05) and atopy by prick test (<0.01). These results point to the need to evaluate atopic status in workers and identify the most susceptible subjects, with the aim of informing them of their at-risk status and monitoring their progress. This makes it possible to diagnose sooner those symptoms possibly indicative of a work-related disease, because even in presence of good environmental conditions and even when symptoms are mild, it is almost always the atopic subjects who are affected. Am. J. Ind. Med. 34:623–627, 1998. © 1998 Wiley-Liss, Inc.     

Urinary Concentrations of (+)-Catechin and (-)-Epicatechin as Biomarkers of Dietary Intake of Flavan-3-ols in the European Prospective Investigation into Cancer and Nutrition (EPIC) Study

This study examines the correlation of acute and habitual dietary intake of flavan-3-ol monomers, proanthocyanidins, theaflavins, and their main food sources with the urinary concentrations of (+)-catechin and (-)-epicatechin in the European Prospective Investigation into Cancer and Nutrition study (EPIC). Participants (N = 419, men and women) provided 24-h urine samples and completed a 24-h dietary recall (24-HDR) on the same day. Acute and habitual dietary data were collected using a standardized 24-HDR software and a validated dietary questionnaire, respectively. Intake of flavan-3-ols was estimated using the Phenol-Explorer database. Concentrations of (+)-catechin and (-)-epicatechin in 24-h urine were analyzed using tandem mass spectrometry after enzymatic deconjugation. Simple and partial Spearman’s correlations showed that urinary concentrations of (+)-catechin, (-)-epicatechin and their sum were more strongly correlated with acute than with habitual intake of individual and total monomers (acute r_partial = 0.13–0.54, p < 0.05; and habitual r_partial = 0.14–0.28, p < 0.01), proanthocyanidins (acute r_partial = 0.24–0.49, p < 0.001; and habitual r_partial = 0.10–0.15, p < 0.05), theaflavins (acute r_partial = 0.22–0.31, p < 0.001; and habitual r_partial = 0.20–0.26, p < 0.01), and total flavan-3-ols (acute r_partial = 0.40–0.48, p < 0.001; and habitual r_partial = 0.23–0.33, p < 0.001). Similarly, urinary concentrations of flavan-3-ols were weakly correlated with both acute (r_partial = 0.12–0.30, p < 0.05) and habitual intake (r_partial = 0.10–0.27, p < 0.05) of apple and pear, stone fruits, berries, chocolate and chocolate products, cakes and pastries, tea, herbal tea, wine, red wine, and beer and cider. Moreover, all comparable correlations were stronger for urinary (-)-epicatechin than for (+)-catechin. In conclusion, our data support the use of urinary concentrations of (+)-catechin and (-)-epicatechin, especially as short-term nutritional biomarkers of dietary catechin, epicatechin and total flavan-3-ol monomers.     

The influence of different types of preparation (espresso and brew) on coffee aroma and main bioactive constituents

Abstract

Coffee is one of the most popular hot drinks in the world; it may be prepared by several methods, but the most common forms are boiled (brew) and pressurized (espresso). Analytical studies on the substances responsible for the pleasant aroma of roasted coffee have been carried out for more than 100 years. Brew coffee and espresso coffee (EC) have a different and peculiar aroma profile, demonstrating the importance of the brewing process on the final product sensorial quality. Concerning bioactive compounds, the extraction mechanism plays a crucial role. The differences in the composition of coffee brew in chlorogenic acids and caffeine content is the result of the different procedures of coffee preparation. The aim of the present review is to detail how the brewing process affects coffee aroma and composition.     

In vitro studies on the stability in the proximal gastrointestinal tract and bioaccessibility in Caco-2 cells of chlorogenic acids from spent coffee grounds

Abstract

Spent coffee grounds are a potential commercial source of substantial amounts of chlorogenic acids (CGAs). The aim of this study was to evaluate the stability of spent coffee CGAs using in vitro simulated gastroduodenal digestion and to investigate their potential absorption using an in vitro Caco-2 model of human small intestinal epithelium. During in vitro digestion, lactones were partially degraded while caffeoylquinic and feruloylquinic acids were much more stable. Transport and metabolism studies showed that 1% of the total CGAs were absorbed and transported from the apical to the basolateral side of a Caco-2 cell monolayer after 1?h. Lactones and coumaroylquinic acids showed the rate of highest absorption. Caco-2 cells possessed low metabolic activity. In conclusion, spent coffee extracts contain large amounts of CGAs, which remained bioaccessible across the intestinal barrier, albeit to a relatively low degree.     

绿茶多酚对心理应激大鼠行为表现的影响

目的观察绿茶多酚对心理应激大鼠行为、认知行为以及学习和记忆能力的影响。方法将Wistar大鼠随机分为5组:正常对照组(CT)、应激对照组(SCT)和低、中、高剂量GTPs干预应激组(SLG、SMG和SHG)。采用束缚应激3周建立心理应激动物模型。通过旷场实验了解动物的自主探究行为改变,以水迷宫实验检验动物的认知行为,以避暗实验检测动物的学习和记忆能力。分别以放免法、化学荧光法、双抗夹心ELISA法检测血浆皮质醇水平、去甲肾上腺素和多巴胺含量以及IL-6和IL-2水平。结果各应激组动物的血浆皮质醇水平明显升高,SMG组和SHG组血浆皮质醇与CT组相比显著升高,但较SCT组明显降低。与CT组相比,SCT组动物在旷场中的潜伏期延长,其穿格数、直立次数减少;SLG组动物的表现与SCT组相近,而SMG组和SHG组动物只出现穿格数的减少,而且,SMG组和SHG组动物的潜伏期和直立次数与SCT组比较也存在显著性差异。避暗反应结果显示,各应激组动物的潜伏期均明显延长,而电击次数仅在SCT组和SLG组动物出现显著增加。水迷宫测试显示,与CT组比较,SCT组和SLG组动物完成水迷宫所需的时间和发生错误的次数均明显增加。另外,与SCT组相比,SMG组和SHG组动物完成水迷宫所需的时间和错误次数以及避暗反应电击次数均明显降低。各应激组动物在束缚应激后,其血浆IL-6和IL-2水平均明显升高;SCT组和SLG组动物血浆NE和DA水平显著降低,而SMG组和SHG组动物未见显著性变化。与SCT组相比,SMG组和SHG组动物血浆NE和DA水平明显升高,且血浆IL-6含量亦显著增加。结论心理应激引起动物应激激素分泌增加,行为学表现异常,而适量补充GTPs可改善心理应激机体的行为学表现,提高应激机体的自主活动和探究行为、认知功能以及学习、记忆能力。     

Effects of Ingesting Both Catechins and Chlorogenic Acids on Glucose,Incretin, and Insulin Sensitivity in Healthy Men: A Randomized,Double-Blinded,Placebo-Controlled Crossover Trial

Epidemiologic studies have revealed that consuming green tea or coffee reduces diabetes risk. We evaluated the effects of the combined consumption of green tea catechins and coffee chlorogenic acids (GTC+CCA) on postprandial glucose, the insulin incretin response, and insulin sensitivity. Eleven healthy men were recruited for this randomized, double-blinded, placebo-controlled crossover trial. The participants consumed a GTC+CCA-enriched beverage (620 mg GTC, 373 mg CCA, and 119 mg caffeine/day) for three weeks; the placebo beverages (PLA) contained no GTC or CCA (PLA: 0 mg GTC, 0 mg CCA, and 119 mg caffeine/day). Postprandial glucose, insulin, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) responses were measured at baseline and after treatments. GTC+CCA consumption for three weeks showed a significant treatment-by-time interaction on glucose changes after the ingestion of high-fat and high-carbohydrate meals, however, it did not affect fasting glucose levels. Insulin sensitivity was enhanced by GCT+CCA compared with PLA. GTC+CCA consumption resulted in a significant increase in postprandial GLP-1 and a decrease in GIP compared to PLA. Consuming a combination of GTC and CCA for three weeks significantly improved postprandial glycemic control, GLP-1 response, and postprandial insulin sensitivity in healthy individuals and may be effective in preventing diabetes.     

Dietary chlorogenic acid regulates gut microbiota,serum-free amino acids and colonic serotonin levels in growing pigs

Chlorogenic acid (CGA) has many biological properties, including antibacterial, antioxidant and anti‐inflammatory properties, and is one of the most abundant phenolic acids available in the human diet. The aim of this study was to investigate the effects of CGA on regulation of the gut microbiota, and on the levels of free amino acids and 5-hydroxytryptamine (5-HT, serotonin). Ninety-six healthy growing pigs were randomly assigned to two treatment groups: the Ctrl group (control group, standard feed) and the CGA group [standard feed plus 0.05% 3-caffeoylquinic acid (3-CQA)] for 60?days. The diversity of the gut microbiota was increased after CGA supplementation. Changes in these microbes were significantly associated with the serum free amino acid levels and colonic 5-HT level. Compared with the Ctrl group, the levels of serum aspartic acid, threonine, alanine, arginine, and colonic 5-HT were significantly increased (p?相似文献   

茶多酚抗动脉粥样硬化机制研究

目的　观察茶多酚在高脂饲料诱发家兔动脉粥样硬化过程中各种抗氧化和氧化指标的动态变化。方法　选取 1 5～ 2 0kg的家兔 2 4只 ,随机分为 4组 :正常对照组、动脉粥样硬化模型组、低剂量茶多酚组和高剂量茶多酚组。分别于实验前、6周末和 12周末测定血清谷胱甘肽过氧化物酶 (GSH -Px)、红细胞超氧化物歧化酶 (RBC -SOD)活性和血清丙二醛 (MDA)含量。 12周末空气栓塞处死家兔 ,迅速剥离主动脉弓 ,进行病理学检查。结果　动脉粥样硬化模型组家兔血清MDA升高 ,GSH -Px、RBC -SOD活性下降 ,主动脉弓内膜下充满泡沫细胞和粥样斑块 ;而茶多酚能降低血清中MDA含量 (P <0 0 5 ) ,诱导家兔体内GSH -Px、RBC -SOD活性增强 (P <0 0 5 ) ,在一定程度上减轻高脂饲料诱发的家兔动脉粥样硬化程度。结论　抗氧化活性可能是茶多酚预防和改善动脉粥样硬化作用的重要机制之一。