Proanthocyanidins and Flavan-3-Ols in the Prevention and Treatment of Periodontitis—Antibacterial Effects

Flavan-3-ols and their oligomeric forms called proanthocyanidins are polyphenolic compounds occurring in several foodstuffs and in many medicinal herbs. Their consumption is associated with numerous health benefits. They exhibit antioxidant, anti-inflammatory, cytoprotective, as well as antimicrobial activity. The latter property is important in the prevention and treatment of periodontal diseases. Periodontitis is a multifactorial polymicrobial infection characterized by a destructive inflammatory process affecting the periodontium. Using non-toxic and efficient natural products such as flavanol derivatives can significantly contribute to alleviating periodontitis symptoms and preventing the disease’s progress. Therefore, a comprehensive systematic review of proanthocyanidins and flavan-3-ols in the prevention and treatment of periodontitis was performed. The present paper reviews the direct antibacterial effects of these compounds against periodontic pathogens. The immunomodulatory effects, including animal and clinical studies, are included in a separate, parallel article. There is significant evidence supporting the importance of the antibacterial action exerted by proanthocyanidins from edible fruits, tea, and medicinal herbs in the inhibition of periodontitis-causing pathogens.     

Polyphenolics in grape seeds-biochemistry and functionality

Grape seeds are waste products of the winery and grape juice industry. These seeds contain lipid, protein, carbohydrates, and 5-8% polyphenols depending on the variety. Polyphenols in grape seeds are mainly flavonoids, including gallic acid, the monomeric flavan-3-ols catechin, epicatechin, gallocatechin, epigallocatechin, and epicatechin 3-O-gallate, and procyanidin dimers, trimers, and more highly polymerized procyanidins. Grape seed extract is known as a powerful antioxidant that protects the body from premature aging, disease, and decay. Grape seeds contains mainly phenols such as proanthocyanidins (oligomeric proanthocyanidins). Scientific studies have shown that the antioxidant power of proanthocyanidins is 20 times greater than vitamin E and 50 times greater than vitamin C. Extensive research suggests that grape seed extract is beneficial in many areas of health because of its antioxidant effect to bond with collagen, promoting youthful skin, cell health, elasticity, and flexibility. Other studies have shown that proanthocyanidins help to protect the body from sun damage, to improve vision, to improve flexibility in joints, arteries, and body tissues such as the heart, and to improve blood circulation by strengthening capillaries, arteries, and veins. The most abundant phenolic compounds isolated from grape seed are catechins, epicatechin, procyanidin, and some dimers and trimers.     

Updated bioavailability and 48 h excretion profile of flavan-3-ols from green tea in humans

Green tea is a popular beverage, prepared with infusion of unfermented dried leaves of Camellia sinensis, and is one of the most relevant sources of polyphenolic compounds in the human diet. This study reports green tea flavan-3-ol absorption, metabolism and complete urinary excretion up to 48?h in 20 healthy volunteers. Urinary and tea samples were analysed by high-performance liquid chromatography coupled with tandem mass spectrometry. Green tea contained monomeric flavan-3-ols and proanthocyanidins with a total polyphenol content of 728?μmol. A total of 41 metabolites were identified in urines, all present in conjugated forms. Among these, six colonic metabolites of green tea flavan-3-ols were identified for the first time after green tea consumption in humans. The average 48?h bioavailability was close to 62%, major contributors being microbial metabolites. Some volunteer showed a 100% absorption/excretion, whereas some others were unable to efficiently absorb/excrete this class of flavonoids. This suggests that colonic ring fission metabolism could be relevant in the putative bioactivity of green tea polyphenols.     

Tea flavan-3-ols as modulating factors in endoplasmic reticulum function

Regular green tea consumption has been shown to reduce the risk of cancer and diabetes mellitus. These effects are attributed to tea flavan-3-ols, especially to epigallocatechin gallate; however, the molecular targets and mechanisms of action are still subject of extensive research. The special roles of the endoplasmic reticulum (ER) in biotransformation, protein synthesis, calcium homeostasis, and glucose production make this organelle a potential target of the antitumor and antidiabetic effects of tea flavan-3-ols. The purpose of this review is to present evidence for the biologic actions of tea flavan-3-ols on specific ER targets associated with normal function and disease. Reactivation of chemical carcinogens can be reduced by tea flavan-3-ols through inhibition of glucuronide transport across the ER membrane. Catechins modulate Ca²⁺ release from the ER lumen and interfere with glycoprotein maturation, which can lead to decreased viability and increased drug sensitivity of tumor cells. Epigallocatechin gallate inhibits glucose transport across the ER membrane, which can underlie the reduction of hepatic glucose production by tea flavan-3-ols. These mechanisms likely contribute to the chemopreventive and glucose-lowering effects of tea catechins. Investigating the effects of flavan-3-ols on ER functions is a promising field of medical and biochemical research to understand disease and improve health.     

Comprehensive analysis of phenolic compounds and abscisic acid profiles of twelve native Canadian berries

Wild berries, integral parts of North American Natives’ traditional nutrition, are a rich source of phytochemicals involved in the prevention of metabolic syndrome. Although phenolic compounds are generally considered to be the functional components in fruits, the identification of specific compounds in relation to this beneficial activity remains to be uncovered. With the long-term goal of establishing the contribution of phytochemical compounds to their beneficial health effects, we investigated in a comprehensive manner the composition of twelve native Canadian berries: Saskatoon berry, alpine bearberry, chokeberry, black crowberry, honeysuckle, chokecherry, cloudberry, elderberry, lowbush blueberry, alpine blueberry, lingonberry and highbush cranberry. All harvested in the province of Quebec, these fruits were analyzed for their phenolic composition (anthocyanins, flavonols, flavan-3-ols, phenolic acids, proanthocyanidins and ellagitannins) and their content in abscisic acid derivatives (cis- and trans-ABA, abscisic acid-glucose ester, 7′-hydroxy-abscisic acid, neo-phaseic acid, phaseic acid and dihydrophaseic acid). Over 60 different phenolic compounds were identified and quantified in berries. Along with the characterization of abscisic acid, this study reports for the first time a complete characterization of proanthocyanidins in these fruits, highbush cranberry presenting the highest content of this class of compounds.     

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.     

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.     

Chemical characterisation of Malvar grape seeds (Vitis vinifera L.) by ultrafiltration and RP-HPLC-PAD-MS

A combination of fast ultrafiltration clean-up procedure and enhanced resolution RP-HPLC-PAD-MS analytical technique is proposed for the characterisation of low molecular mass extractable phytochemicals from Malvar grape seeds (Vitis vinifera L.). This methodology offers satisfactory resolution of the main procyanidin dimers and some trimers and tetramers. Thirty-nine peaks were identified. Seventeen of them contained 17 unambiguously identified compounds: 3 flavan-3-ol monomers (C, EC and ECG), 6 procyanidin dimers (B₁, B₂, B₃, B₄, B₅ and B₆), 1 procyanidin trimer (C₁), 1 procyanidin tetramer ([EC-(4α-8)-EC-(4α-8)-EC-(4α-8)-EC]), 4 hydroxybenzoic derivatives (gallic and protocatechuic acids, protocatechuic aldehyde and methyl gallate*), 1 amino acid (tryptophan)* and ellagic acid*. The remaining 22 peaks, and 1 of the first 17 contained 26 compounds which were tentatively identified as: 2 procyanidin dimers (A- and B-type), 7 trimers, 3 tetramers, 7 monogalloylated dimers, 2 monogalloylated trimers and 1 digalloylated dimer, besides 1 gallotannin, 1 dihydroflavonol* and 2 ellagitannins, some of them described for first time in V. vinifera species. Flavan-3-ols represented 62.4% of all grape seed constituents, absorbing at 280 nm, whereas the non-flavan-3-ol species accounted for more than one-third of the total extractable grape seed constituents.     

Discrimination of five Greek red grape varieties according to the anthocyanin and proanthocyanidin profiles of their skins and seeds

The knowledge of grapes phenolic content is proven to be critical for the vinification process and the improvement of wine quality. This study was undertaken to determine the phenolic composition and to employ the phenolic profile as a varietal discrimination tool in five Greek red grape varieties. Ninety grape samples from two seasons (2017 and 2018) were analyzed after extraction with organic solvents. Their proanthocyanidin profile, expressed as percentages of flavan-3-ols, was determined in both skins and seeds by employing phloroglucinolysis followed by HPLC-UV and MS detection, and anthocyanin profile was identified only in the skin extracts by HPLC-UV. Significant differences were observed in proanthocyanidin and anthocyanin profiles of skin extracts between the samples of different varieties, but not in seeds. (-)-Epicatechin was the main subunit in Mandilaria, Kotsifali, Agiorgitiko and Xinomavro grapes while (-)-epigallocatechin gallate in Mavrotragano. Malvidin-3-O-glucoside was the predominant pigment in all grape samples analyzed with the exception of Kotsifali skin extracts, where peonidin-3-O-glucoside was the most abundant anthocyanin. In addition, Mavrotragano skin extracts were the richest in delphinidin and petunidin-3-O-glucosides, while Agiorgitiko and Xinomavro contained the highest amount of malvidin-3-O-glucoside. The results underline the significance of the skin phenolic composition as a tool for the discrimination of the Greek red grape varieties.     

The absorption, metabolism and excretion of flavan-3-ols and procyanidins following the ingestion of a grape seed extract by rats

Rats were fed a grape seed extract (GSE) containing (+)-catechin, (-)-epicatechin and dimers, trimers, tetramers and polymeric procyanidins. Liver, kidney, brain and gastrointestinal (GI) tract together with plasma, urine and faeces were collected over a 24 h period and their flavan-3-ol content was analysed by HPLC with tandem mass spectrometry and diode array detection. Small amounts of the GSE flavan-3-ols moved out of the stomach and into the duodenum/jejunum, and to a greater extent the ileum 1 h after ingestion, and into the caecum after 2 h with relatively small amounts being detected in the colon after 3 h. The GI tract contained the parent GSE flavan-3-ols and procyanidins with only trace amounts of metabolites and there were no indications that proanthocyanidins were depolymerised in the GI tract releasing monomeric flavan-3-ols. Plasma contained exclusively catechin glucuronides and methylated glucuronide metabolites which were also detected in the liver and kidneys. These metabolites were also present in urine together with sulphated metabolites and low amounts of the procyanidin dimers B1, B2, B3 and B4 as well as the trimer C2 and an unknown GSE trimer. The amounts of (+)-catechin and (-)-epicatechin metabolites excreted in urine relative to the quantity of the monomers ingested were 27 and 36 %, respectively, after 24 h. This is similar to the levels of urinary excretion reported to occur by other investigators after feeding (-)-epicatechin to rats and provides further, albeit indirect, evidence that the procyanidin oligomers in the GSE were not depolymerised to monomers to any extent after ingestion. No convincing analytical data were obtained for the presence of flavan-3-ol metabolites in the brain.     

Effect of the growing area on the methylxanthines and flavan-3-ols content in cocoa beans from Ecuador

Nacional is a worldwide recognized Ecuadorian cocoa variety. However, little is known regarding its phytochemical profile and how the production area influences its nutritional quality. The contents of methylxanthines (caffeine and theobromine), total polyphenols, flavan-3-ols monomers (catechin and epicatechin) and main proanthocyanidins (procyanidins B2 and C1) in beans of Nacional cocoa were evaluated. A comprehensive sampling was carried out along Ecuador, including 85 farms from three different geographical levels (region, province, and canton). Theobromine and caffeine contents were higher in cocoas from the Amazonian region. According to the caffeine/theobromine ratio, all samples were classified as Trinitario cocoa. The flavan-3-ols amount was not clearly associated to a geographical area. However, when principal component analysis was applied, common patterns were found for some provinces. These results may be useful to further characterize the composition of cocoa beans for quality and authenticity purposes and the development of chocolate products rich in bioactives.     

Bioavailability of catechins from ready-to-drink tea

ObjectiveBecause consumption of teas may be associated with potential health benefits due to its content in polyphenols and in Western countries the consumption of tea is equally divided between the hot and the ready-to-drink (RTD) cold versions of this typical beverage, the aim of this work was to study the absorption and metabolism of flavan-3-ols in human volunteers after the ingestion of a commercial RTD tea.MethodsA feeding study was carried out in 20 healthy human volunteers and urine samples were collected for 24 h after tea ingestion. Flavan-3-ols–derived molecules were identified and quantified in urine samples by high-performance liquid chromatography with tandem mass spectrometric detection.ResultsEight relevant metabolites were identified in urine, all modified flavan-3-ols with the exception of unmetabolized gallic acid. The urinary excretion of flavan-3-ols was equal to 7.2% of the intake with tea. Gallic acid, which was abundant in the RTD tea used in this study, reached a 4.5% of the drunken amount.ConclusionsThe bioavailability values observed are in agreement with previous reports, although the dosage of polyphenols ingested in this study is remarkably lower. Moreover, the use of a group of 20 volunteers, more than the average number of subjects used for usual human acute-feeding studies involving polyphenols, provides additional credibility to the results. After drinking the RTD ice tea used in this study, the internal compartments are exposed to non-marginal doses of flavanols and flavanol metabolites up to 24 h.     

New nutrition, proteomics, and how both can enhance studies in cancer prevention and therapy

The increased application of MS technologies to nutrition and cancer prevention research has enabled unique insights into the health benefits of polyphenols. Polyphenols are phytochemicals that appear to have chemical properties that provide valuable health benefits when ingested. In particular, experiments have suggested that grape seed proanthocyanidins, oligomers of the catechin family of polyphenols, may have health benefits, possibly due to their capacity to be oxidized. Two-dimensional gel proteomics technology identified specific rat brain proteins that were differentially affected after ingestion of grape seed extract. Beneficial changes in the expression of these proteins were observed relative to changes seen in the brains of Alzheimer disease patients at autopsy and of transgenic mouse models of dementia. These findings were consistent with the hypothesis that grape seed polyphenols may have neuroprotective activity. Previous experiments showed that grape seed extract was significantly chemopreventive in a rat model of breast cancer, but this depended on the specific diet in which the grape seed was administered. Thus, phytochemicals such as polyphenols may have health benefits in mammalian tissues unrelated to classical nutritional deficiency models. This report illustrates how experimental approaches that combine proteomics technologies with a dietary intervention with specific phytochemicals in normal animals can enhance studies on cancer prevention and treatment.     

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.     

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.     

Bioavailability of polyphenon E flavan-3-ols in humans with an ileostomy

To investigate the degree of absorption of flavan-3-ols in the small intestine, human subjects with an ileostomy ingested 200 mg of Polyphenon E, a green tea extract, after which ileal fluid and urine, collected over a 24-h period, were analyzed by high-performance liquid chromatography with photodiode array and mass spectrometric detection. The data obtained indicated that although approximately 40% of flavan-3-ol intake is recovered in ileal fluid, substantial quantities are absorbed in the small intestine. Moreover, 14 urinary metabolites, comprising sulfates, glucuronide, and methylated derivatives, were identified and quantified. All were metabolites of (epi)catechin or (epi)gallocatechin, representing 47 +/- 2% and 26 +/- 9%, respectively, of the ingested parent compound. These high recoveries indicate that these flavan-3-ols absorbed in the small intestine are much more bioavailable than most dietary flavonoids. No 3-O-galloylated flavan-3-ols or their metabolites were detected in urine. The absence of urinary flavan-3-ol metabolites after ingestion of 200 mg of (-)-epigallocatechin gallate indicates that there is no removal of the 3-O-galloyl group in vivo, and hence, this does not account for the high urinary recovery of (epi)gallocatechin metabolites after ingestion of Polyphenon E. Increasing the intake of Polyphenon E, by feeding doses of 200, 500, and 1500 mg, led to increased urinary excretion of (epi)catechin metabolites but not metabolites of (epi)gallocatechin. Coingestion of 200 mg of Polyphenon E with bread, cheese, or glucose did not significantly modify the absorption, metabolism, and excretion of flavan-3-ols. It does not necessarily follow, however, that the same would occur when flavan-3-ols are ingested with more complex food matrices.     

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

Following acute ingestion of green tea by six human subjects, HPLC-MS2 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.     

Quality assessment of commercial dietary antioxidant products from Vitis vinifera L. grape seeds

Phenolic preparations from Vitis vinifera L. grape seeds are products commonly used in the formulation of dietary antioxidant supplements. In this article, we used a methodology (the oxygen radical absorbance capacity, ORAC) to evaluate the in vitro antioxidant capacity of commercial dietary grape seed products and studied the relationship of the antioxidant capacity with the phenolic composition of these products. The ORAC value of the different brands of commercial products studied (n = 16) varied from 2.71 to 26.4 micromol Trolox equivalents/mg (approximately equal to 10-fold difference). For four of these products, the batch-to-batch ORAC variation, expressed as a coefficient of variation of the mean, was 10.5% (n = 6), 13.1% (n = 3), 19.4% (n = 4), and 7.8% (n = 4). Analysis of monomeric and oligomeric flavan-3-ols by liquid chromatography-diode array detection (LC-DAD)/electrospray-mass spectrometry and procyanidins by thiolysis-LC-DAD also revealed large differences among the commercial grape seed products. Moreover, the ORAC value could be fitted to a regression model using variables from contents of individual phenolic compounds and procyanidins. The product-to-product and batch-to-batch variation in ORAC values and flavan-3-ol composition found among the commercial products studied demonstrated that they are poorly standardized, resulting in inconsistent composition and biological activity.     

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.     

Bioavailability of coffee chlorogenic acids and green tea flavan-3-ols

This paper reviews recent human studies on the bioavailability of chlorogenic acids in coffee and green tea flavan-3-ols in which the identification of metabolites, catabolites and parent compounds in plasma, urine and ileal fluid was based on mass spectrometric methodology. Both the chlorogenic acids and the flavan-3-ols are absorbed in the small intestine and appear in the circulatory system predominantly as glucuronide, sulfate and methylated metabolites. Even when absorption occurs in the small intestine, feeding studies with ileostomists reveal that substantial amounts of the parent compounds and some of their metabolites appear in ileal fluid indicating that in volunteers with a functioning colon these compounds will pass to the large intestine where they are subjected to the action of the colonic microflora. A diversity of colonic-derived catabolites are absorbed into the bloodstream and pass through the body prior to excretion in urine. There is growing evidence that these compounds, which were little investigated until recently, are produced in quantity in the colon and form a key part of the bioavailability equation of flavonoids and related compounds that occur in fruits, vegetables and beverages. Recent evidence indicates that some colon-derived phenolic acids have in vitro anti-inflammatory activity.