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Alan Crozier - One of the best experts on this subject based on the ideXlab platform.
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distribution and biosynthesis of Flavan 3 ols in camellia sinensis seedlings and expression of genes encoding biosynthetic enzymes
Phytochemistry, 2010Co-Authors: Hiroshi Ashihara, William Mullen, Weiwei Deng, Alan CrozierAbstract:Abstract The distribution of phenolic compounds in young and developing leaves, stems, main and lateral roots and cotyledons of 8-week-old tea (Camellia sinensis) seedlings was investigated using HPLC-MS2. Fourteen compounds, Flavan-3-ols, chlorogenic acids, and kaempferol-O-glycosides, were identified on the basis of their retention time, absorbance spectrum, and MS fragmentation pattern. The major phenolics were (−)-epigallocatechin-3-O-gallate and (−)-epicatechin-3-O-gallate, located principally in the green parts of the seedlings. Considerable amounts of radioactivity from [ring-14C]phenylalanine were incorporated in (−)-epicatechin, (−)-epigallocatechin, (−)-epicatechin-3-O-gallate and (−)-epigallocatechin-3-O-gallate, by tissues of young and developing leaves and stems. Expression of genes encoding enzymes involved in Flavan-3-ol biosynthesis, CHS, CHI, F3H, F3′5′H, DFR, ANS, ANR and LAR was investigated. Transcripts of all genes, except LAR, were more abundant in leaves and stems than in roots and cotyledons. No significant difference was found in the amount of transcript of LAR. These findings indicate that in tea seedlings Flavan-3-ols are produced by a naringenin-chalcone → naringenin → dihydrokaempferol pathway. Dihydrokaempferol is a branch point in the synthesis of (−)-epigallocatechin-3-O-gallate and other Flavan-3-ols which can be formed by routes beginning with either a flavonoid 3′-hydroxylase mediated conversion of the flavonol to dihydroquercetin or a flavonoid 3′,5′-hydroxylase-catalysed conversion to dihydromyricetin with subsequent steps involving sequential reactions catalysed by dihydroFlavanol 4-reductase, anthocyanidin synthase, anthocyanidin reductase and Flavan-3-ol gallate synthase.
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absorption metabolism and excretion of green tea Flavan 3 ols in humans with an ileostomy
Molecular Nutrition & Food Research, 2010Co-Authors: Angelique Stalmach, Michael E J Lean, William Mullen, Heike Steiling, Gary Williamson, Alan CrozierAbstract:Green tea containing 634 micromol of Flavan-3-ols was ingested by human subjects with an ileostomy. Ileal fluid, plasma, and urine collected 0-24 h after ingestion were analysed by HPLC-MS. The ileal fluid contained 70% of the ingested Flavan-3-ols in the form of parent compounds (33%) and 23 metabolites (37%). The main metabolites effluxed back into the lumen of the small intestine were O-linked sulphates and methyl-sulphates of (epi)catechin and (epi)gallocatechin. Thus, in subjects with a functioning colon substantial quantities of Flavan-3-ols would pass from the small to the large intestine. Plasma contained 16 metabolites, principally methylated, sulphated, and glucuronidated conjugates of (epi)catechin and (epi)gallocatechin, exhibiting 101-256 nM peak plasma concentration and the time to reach peak plasma concentration ranging from 0.8 to 2.2 h. Plasma pharmacokinetic profiles were similar to those obtained with healthy subjects, indicating that Flavan-3-ol absorption occurs in the small intestine. Ileostomists had earlier plasma time to reach peak plasma concentration values than subjects with an intact colon, indicating the absence of an ileal brake. Urine contained 18 metabolites of (epi)catechin and (epi)gallocatechin in amounts corresponding to 6.8+/-0.6% of total Flavan-3-ol intake. However, excretion of (epi)catechin metabolites was equivalent to 27% of the ingested (-)-epicatechin and (+)-catechin.
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green tea Flavan 3 ols colonic degradation and urinary excretion of catabolites by humans
Journal of Agricultural and Food Chemistry, 2010Co-Authors: Suri Roowi, Michael E J Lean, Christine A Edwards, William Mullen, Angelique Stalmach, Alan CrozierAbstract:Following the ingestion of green tea, substantial quantities of Flavan-3-ols pass from the small to the large intestine (Stalmach et al. Mol. Nutr. Food Res. 2009, 53, S44-S53; Mol. Nutr. Food Res. 2009, doi: 10.1002/mnfr.200900194). To investigate the fate of the Flavan-3-ols entering the large intestine, where they are subjected to the action of the colonic microflora, (-)-epicatechin, (-)-epigallocatechin, and (-)-epigallocatechin-3-O-gallate were incubated in vitro with fecal slurries and the production of phenolic acid catabolites was determined by GC-MS. In addition, urinary excretion of phenolic catabolites was investigated over a 24 h period after ingestion of either green tea or water by healthy volunteers with a functioning colon. The green tea was also fed to ileostomists, and 0-24 h urinary excretion of phenolic acid catabolites was monitored. Pathways are proposed for the degradation of green tea Flavan-3-ols in the colon and further catabolism of phenolic compounds passing into the circulatory system from the large intestine, prior to urinary excretion in quantities corresponding to ca. 40% of intake compared with ca. 8% absorption of Flavan-3-ol methyl, glucuronide, and sulfate metabolites in the small intestine. The data obtained point to the importance of the colonic microflora in the overall bioavailability and potential bioactivity of dietary flavonoids.
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Milk decreases urinary excretion but not plasma pharmacokinetics of cocoa Flavan-3-ol metabolites in humans
The American Journal of Clinical Nutrition, 2009Co-Authors: William Mullen, Jennifer L Donovan, Michael E J Lean, Gina Borges, Mauro Serafini, Christine A Edwards, Alan CrozierAbstract:Background: Cocoa drinks containing Flavan-3-ols are associated with many health benefits, and conflicting evidence exists as to whether milk adversely affects the bioavailability of Flavan-3-ols. Objective: The objective was to determine the effect of milk on the bioavailability of cocoa Flavan-3-ol metabolites. Design: Nine human volunteers followed a low-flavonoid diet for 2 d before drinking 250 mL of a cocoa beverage, made with water or milk, that contained 45 mu mol (-)-epicatechin and (-)-catechin. Plasma and urine samples were collected for 24 h, and Flavan-3-ol metabolites were analyzed by HPLC with photodiode array and mass spectrometric detection. Results: Milk affected neither gastric emptying nor the transit time through the small intestine. Two Flavan-3-ol metabolites were detected in plasma and 4 in urine. Milk had only minor effects on the plasma pharmacokinetics of an (epi) catechin-O-sulfate and had no effect on an O-methyl-(epi) catechin-O-sulfate. However, milk significantly lowered the excretion of 4 urinary Flavan-3-ol metabolites from 18.3% to 10.5% of the ingested dose (P=0.016). Studies that showed protective effects of cocoa and those that showed no effect of milk on bioavailability used products that have a much higher Flavan 3-ol content than does the commercial cocoa used in the present study. Conclusions: Most studies of the protective effects of cocoa have used drinks with a very high Flavan-3-ol content. Whether similar protective effects are associated with the consumption of many commercial chocolate and cocoa products containing substantially lower amounts of Flavan-3-ols, especially when absorption at lower doses is obstructed by milk, remains to be determined.
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Bioavailability of Polyphenon E Flavan-3-ols in Humans with an Ileostomy
The Journal of nutrition, 2008Co-Authors: Cyril Auger, William Mullen, Alan CrozierAbstract: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.
William Mullen - One of the best experts on this subject based on the ideXlab platform.
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distribution and biosynthesis of Flavan 3 ols in camellia sinensis seedlings and expression of genes encoding biosynthetic enzymes
Phytochemistry, 2010Co-Authors: Hiroshi Ashihara, William Mullen, Weiwei Deng, Alan CrozierAbstract:Abstract The distribution of phenolic compounds in young and developing leaves, stems, main and lateral roots and cotyledons of 8-week-old tea (Camellia sinensis) seedlings was investigated using HPLC-MS2. Fourteen compounds, Flavan-3-ols, chlorogenic acids, and kaempferol-O-glycosides, were identified on the basis of their retention time, absorbance spectrum, and MS fragmentation pattern. The major phenolics were (−)-epigallocatechin-3-O-gallate and (−)-epicatechin-3-O-gallate, located principally in the green parts of the seedlings. Considerable amounts of radioactivity from [ring-14C]phenylalanine were incorporated in (−)-epicatechin, (−)-epigallocatechin, (−)-epicatechin-3-O-gallate and (−)-epigallocatechin-3-O-gallate, by tissues of young and developing leaves and stems. Expression of genes encoding enzymes involved in Flavan-3-ol biosynthesis, CHS, CHI, F3H, F3′5′H, DFR, ANS, ANR and LAR was investigated. Transcripts of all genes, except LAR, were more abundant in leaves and stems than in roots and cotyledons. No significant difference was found in the amount of transcript of LAR. These findings indicate that in tea seedlings Flavan-3-ols are produced by a naringenin-chalcone → naringenin → dihydrokaempferol pathway. Dihydrokaempferol is a branch point in the synthesis of (−)-epigallocatechin-3-O-gallate and other Flavan-3-ols which can be formed by routes beginning with either a flavonoid 3′-hydroxylase mediated conversion of the flavonol to dihydroquercetin or a flavonoid 3′,5′-hydroxylase-catalysed conversion to dihydromyricetin with subsequent steps involving sequential reactions catalysed by dihydroFlavanol 4-reductase, anthocyanidin synthase, anthocyanidin reductase and Flavan-3-ol gallate synthase.
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absorption metabolism and excretion of green tea Flavan 3 ols in humans with an ileostomy
Molecular Nutrition & Food Research, 2010Co-Authors: Angelique Stalmach, Michael E J Lean, William Mullen, Heike Steiling, Gary Williamson, Alan CrozierAbstract:Green tea containing 634 micromol of Flavan-3-ols was ingested by human subjects with an ileostomy. Ileal fluid, plasma, and urine collected 0-24 h after ingestion were analysed by HPLC-MS. The ileal fluid contained 70% of the ingested Flavan-3-ols in the form of parent compounds (33%) and 23 metabolites (37%). The main metabolites effluxed back into the lumen of the small intestine were O-linked sulphates and methyl-sulphates of (epi)catechin and (epi)gallocatechin. Thus, in subjects with a functioning colon substantial quantities of Flavan-3-ols would pass from the small to the large intestine. Plasma contained 16 metabolites, principally methylated, sulphated, and glucuronidated conjugates of (epi)catechin and (epi)gallocatechin, exhibiting 101-256 nM peak plasma concentration and the time to reach peak plasma concentration ranging from 0.8 to 2.2 h. Plasma pharmacokinetic profiles were similar to those obtained with healthy subjects, indicating that Flavan-3-ol absorption occurs in the small intestine. Ileostomists had earlier plasma time to reach peak plasma concentration values than subjects with an intact colon, indicating the absence of an ileal brake. Urine contained 18 metabolites of (epi)catechin and (epi)gallocatechin in amounts corresponding to 6.8+/-0.6% of total Flavan-3-ol intake. However, excretion of (epi)catechin metabolites was equivalent to 27% of the ingested (-)-epicatechin and (+)-catechin.
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green tea Flavan 3 ols colonic degradation and urinary excretion of catabolites by humans
Journal of Agricultural and Food Chemistry, 2010Co-Authors: Suri Roowi, Michael E J Lean, Christine A Edwards, William Mullen, Angelique Stalmach, Alan CrozierAbstract:Following the ingestion of green tea, substantial quantities of Flavan-3-ols pass from the small to the large intestine (Stalmach et al. Mol. Nutr. Food Res. 2009, 53, S44-S53; Mol. Nutr. Food Res. 2009, doi: 10.1002/mnfr.200900194). To investigate the fate of the Flavan-3-ols entering the large intestine, where they are subjected to the action of the colonic microflora, (-)-epicatechin, (-)-epigallocatechin, and (-)-epigallocatechin-3-O-gallate were incubated in vitro with fecal slurries and the production of phenolic acid catabolites was determined by GC-MS. In addition, urinary excretion of phenolic catabolites was investigated over a 24 h period after ingestion of either green tea or water by healthy volunteers with a functioning colon. The green tea was also fed to ileostomists, and 0-24 h urinary excretion of phenolic acid catabolites was monitored. Pathways are proposed for the degradation of green tea Flavan-3-ols in the colon and further catabolism of phenolic compounds passing into the circulatory system from the large intestine, prior to urinary excretion in quantities corresponding to ca. 40% of intake compared with ca. 8% absorption of Flavan-3-ol methyl, glucuronide, and sulfate metabolites in the small intestine. The data obtained point to the importance of the colonic microflora in the overall bioavailability and potential bioactivity of dietary flavonoids.
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Milk decreases urinary excretion but not plasma pharmacokinetics of cocoa Flavan-3-ol metabolites in humans
The American Journal of Clinical Nutrition, 2009Co-Authors: William Mullen, Jennifer L Donovan, Michael E J Lean, Gina Borges, Mauro Serafini, Christine A Edwards, Alan CrozierAbstract:Background: Cocoa drinks containing Flavan-3-ols are associated with many health benefits, and conflicting evidence exists as to whether milk adversely affects the bioavailability of Flavan-3-ols. Objective: The objective was to determine the effect of milk on the bioavailability of cocoa Flavan-3-ol metabolites. Design: Nine human volunteers followed a low-flavonoid diet for 2 d before drinking 250 mL of a cocoa beverage, made with water or milk, that contained 45 mu mol (-)-epicatechin and (-)-catechin. Plasma and urine samples were collected for 24 h, and Flavan-3-ol metabolites were analyzed by HPLC with photodiode array and mass spectrometric detection. Results: Milk affected neither gastric emptying nor the transit time through the small intestine. Two Flavan-3-ol metabolites were detected in plasma and 4 in urine. Milk had only minor effects on the plasma pharmacokinetics of an (epi) catechin-O-sulfate and had no effect on an O-methyl-(epi) catechin-O-sulfate. However, milk significantly lowered the excretion of 4 urinary Flavan-3-ol metabolites from 18.3% to 10.5% of the ingested dose (P=0.016). Studies that showed protective effects of cocoa and those that showed no effect of milk on bioavailability used products that have a much higher Flavan 3-ol content than does the commercial cocoa used in the present study. Conclusions: Most studies of the protective effects of cocoa have used drinks with a very high Flavan-3-ol content. Whether similar protective effects are associated with the consumption of many commercial chocolate and cocoa products containing substantially lower amounts of Flavan-3-ols, especially when absorption at lower doses is obstructed by milk, remains to be determined.
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Bioavailability of Polyphenon E Flavan-3-ols in Humans with an Ileostomy
The Journal of nutrition, 2008Co-Authors: Cyril Auger, William Mullen, Alan CrozierAbstract: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.
Robert Luben - One of the best experts on this subject based on the ideXlab platform.
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Biomarker-estimated Flavan-3-ol intake is associated with lower blood pressure in cross-sectional analysis in EPIC Norfolk.
Scientific reports, 2020Co-Authors: Javier I. Ottaviani, Angela A. Mulligan, Marleen A. H. Lentjes, Robert Luben, Abigail Britten, Debora Lucarelli, Reedmond Fong, Nicola Gray, Philip B. Grace, Deborah H. MawsonAbstract:Flavan‐3‐ols are a group of bioactive compounds that have been shown to improve vascular function in intervention studies. They are therefore of great interest for the development of dietary recommendation for the prevention of cardio‐vascular diseases. However, there are currently no reliable data from observational studies, as the high variability in the Flavan‐3‐ol content of food makes it difficult to estimate actual intake without nutritional biomarkers. In this study, we investigated cross‐sectional associations between biomarker‐estimated Flavan‐3‐ol intake and blood pressure and other CVD risk markers, as well as longitudinal associations with CVD risk in 25,618 participants of the European Prospective Investigation into Cancer (EPIC) Norfolk cohort. High Flavan‐ 3‐ol intake, achievable as part of an habitual diet, was associated with a significantly lower systolic blood pressure (− 1.9 (− 2.7; − 1.1) mmHg in men and − 2.5 (− 3.3; − 1.8) mmHg in women; lowest vs highest decile of biomarker), comparable to adherence to a Mediterranean Diet or moderate salt reduction. Subgroup analyses showed that hypertensive participants had stronger inverse association between Flavan‐3‐ol biomarker and systolic blood pressure when compared to normotensive participants. Flavanol intake could therefore have a role in the maintenance of cardiovascular health on a population scale.
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Evaluation at scale of microbiome-derived metabolites as biomarker of Flavan-3-ol intake in epidemiological studies.
Scientific reports, 2018Co-Authors: Javier I. Ottaviani, Robert Luben, Abigail Britten, Debora Lucarelli, Philip B. Grace, Deborah H. Mawson, Redmond Fong, Jennifer Kimball, Jodi L. Ensunsa, Amy TymAbstract:The accurate assessment of dietary intake is crucial to investigate the effect of diet on health. Currently used methods, relying on self-reporting and food composition data, are known to have limitations and might not be suitable to estimate the intake of many bioactive food components. An alternative are nutritional biomarkers, which can allow an unbiased assessment of intake. They require a careful evaluation of their suitability, including: (a) the availability of a precise, accurate and robust analytical method, (b) their specificity (c) a consistent relationship with actual intake. We have evaluated human metabolites of a microbiome-derived Flavan-3-ol catabolite, 5-(3′,4′-dihydroxyphenyl)-[gamma]-valerolactone (gVL), as biomarker of Flavan-3-ol intake in large epidemiological studies. Flavan-3-ols are widely consumed plant bioactives, which have received considerable interest due to their potential ability to reduce CVD risk. The availability of authentic standards allowed the development of a validated high-throughput method suitable for large-scale studies. In dietary intervention studies, we could show that gVL metabolites are specific for Flavan-3-ols present in tea, fruits, wine and cocoa-derived products, with a strong correlation between intake and biomarker (Spearman’s r = 0.90). This biomarker will allow for the first time to estimate Flavan-3-ol intake and further investigation of associations between intake and disease risk.
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Associations between Flavan-3-ol intake and CVD risk in the Norfolk cohort of the European Prospective Investigation into Cancer (EPIC-Norfolk)
Free radical biology & medicine, 2015Co-Authors: Anna Vogiatzoglou, Angela A. Mulligan, Amit Bhaniani, Marleen A. H. Lentjes, Alison Mctaggart, Robert Luben, Christian Heiss, Malte Kelm, Marc W. Merx, Jeremy P. E. SpencerAbstract:Dietary intervention studies suggest that Flavan-3-ol intake can improve vascular function and reduce the risk of cardiovascular diseases (CVD). However, results from prospective studies failed to show a consistent beneficial effect. Associations between Flavan-3-ol intake and CVD risk in the Norfolk arm of the European Prospective Investigation into Cancer and Nutrition (EPIC-Norfolk) were investigated. Data were available from 24,885 (11,252 men; 13,633 women) participants, recruited between 1993 and 1997 into the EPIC-Norfolk study. Flavan-3-ol intake was assessed using 7-day food diaries and the FLAVIOLA Flavanol Food Composition database. Missing data for plasma cholesterol and vitamin C were imputed using multiple imputation. Associations between Flavan-3-ol intake and blood pressure at baseline were determined using linear regression models. Associations with CVD risk were estimated using Cox regression analyses. Median intake of total Flavan-3-ols was 1034 mg/d (range: 0–8531 mg/d) for men and 970 mg/d (0–6695 mg/d) for women, median intake of Flavan-3-ol monomers was 233 mg/d (0–3248 mg/d) for men and 217 (0–2712 mg/d) for women. There were no consistent associations between Flavan-3-ol monomer intake and baseline systolic and diastolic blood pressure (BP). After 286,147 person-years of follow-up, there were 8463 cardiovascular events and 1987 CVD related deaths; no consistent association between Flavan-3-ol intake and CVD risk (HR 0.93, 95% CI: 0.87; 1.00; Q1 vs Q5) or mortality was observed (HR 0.93, 95% CI: 0.84; 1.04). Flavan-3-ol intake in EPIC-Norfolk is not sufficient to achieve a statistically significant reduction in CVD risk.
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assessment of the dietary intake of total Flavan 3 ols monomeric Flavan 3 ols proanthocyanidins and theaflavins in the european union
British Journal of Nutrition, 2014Co-Authors: Anna Vogiatzoglou, Angela A. Mulligan, Marleen A. H. Lentjes, Robert Luben, Christian Heiss, Malte Kelm, Marc W. Merx, Jeremy P. E. Spencer, Hagen Schroeter, Gunter G C KuhnleAbstract:Dietary interventions with Flavan-3-ols have shown beneficial effects on vascular function. The translation of these findings into the context of the health of the general public requires detailed information on habitual dietary intake. However, only limited data are currently available for European populations. Therefore, in the present study, we assessed the habitual intake of Flavan-3-ol monomers, proanthocyanidins (PA) and theaflavins in the European Union (EU) and determined their main food sources using the EFSA (European Food Safety Authority) Comprehensive European Food Consumption Database. Data for adults aged 18–64 years were available from fourteen European countries, and intake was determined using the FLAVIOLA Flavanol Food Composition Database, developed for the present study and based on the latest US Department of Agriculture and Phenol-Explorer databases. The mean habitual intake of Flavan-3-ol monomers, theaflavins and PA ranged from 181 mg/d (Czech Republic) to 793 mg/d (Ireland). The highest intakes of Flavan-3-ol monomers and theaflavins were observed in Ireland (191/505 mg/d) and the lowest intakes in Spain (24/9 mg/d). In contrast, the daily intake of PA was highest in Spain (175 mg/d) and lowest in The Netherlands (96 mg/d). Main sources were tea (62 %), pome fruits (11 %), berries (3 %) and cocoa products (3 %). Tea was the major single contributor to monomer intake (75 %), followed by pome fruits (6 %). Pome fruits were also the main source of PA (28 %). The present study provides important data on the population-based intake of Flavanols in the EU and demonstrates that dietary intake amounts for Flavan-3-ol monomers, PA and theaflavins vary significantly across European countries. The average habitual intake of Flavan-3-ols is considerably below the amounts used in most dietary intervention studies.
Almuth Hammerbacher - One of the best experts on this subject based on the ideXlab platform.
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accumulation of catechin and proanthocyanidins in black poplar stems after infection by plectosphaerella populi hormonal regulation biosynthesis and antifungal activity
Frontiers in Plant Science, 2019Co-Authors: Chhana Ullah, Sybille B Unsicker, Michael Reichelt, Jonathan Gershenzon, Almuth HammerbacherAbstract:Flavan-3-ols including the monomeric catechin and the polymeric proanthocyanidins (PAs) are abundant phenolic metabolites in poplar (Populus spp.) previously described to protect leaves against pathogen infection. However, it is not known whether stems are also defended in this way. Here we investigated Flavan-3-ol accumulation, activity and the regulation of formation in black poplar (P. nigra) stems after infection by a newly described fungal stem pathogen, Plectosphaerella populi, which forms canker-like lesions in stems. We showed that Flavan-3-ol contents increased in P. populi infected black poplar stems over the course of infection compared to non-infected controls. Transcripts of leucoanthocyanidin reductase (LAR) and anthocyanidin reductase (ANR) genes involved in the last steps of Flavan-3-ol biosynthesis were also up-regulated upon fungal infection indicating de novo biosynthesis. Amending culture medium with catechin and PAs reduced the mycelial growth of P. populi, suggesting that these metabolites act as anti-pathogen defenses in poplar in vivo. Among the hormones, salicylic acid (SA) was higher in P. populi infected tissues compared to the non-infected controls over the course of infection studied, while jasmonic acid (JA) and JA-isoleucine (JA-Ile) levels were higher than controls only at the early stages of infection. Interestingly, cytokinins (CKs) were also up-regulated in P. populi-infected stems. Poplar saplings treated with CK showed decreased levels of Flavan-3-ols and SA in stems suggesting a negative association between CK and Flavan-3-ol accumulation. Taken together, the sustained up-regulation of SA in correlation with catechin and proanthocyanidin accumulation suggests that this is the dominant hormone inducing the formation of antifungal Flavan-3-ols during P. populi infection of poplar stems.
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salicylic acid activates poplar defense against the biotrophic rust fungus melampsora larici populina via increased biosynthesis of catechin and proanthocyanidins
New Phytologist, 2019Co-Authors: Chhana Ullah, Sybille B Unsicker, Michael Reichelt, Jonathan Gershenzon, Chungjui Tsai, Liangjiao Xue, Almuth HammerbacherAbstract:Poplar trees synthesize Flavan-3-ols (catechin and proanthocyanidins) as a defense against foliar rust fungi, but the regulation of this defense response is poorly understood. Here, we investigated the role of hormones in regulating Flavan-3-ol accumulation in poplar during rust infection. We profiled levels of defense hormones, signaling genes, and Flavan-3-ol metabolites in black poplar leaves at different stages of rust infection. Hormone levels were manipulated by external sprays, genetic engineering, and drought to reveal their role in rust fungal defenses. Levels of salicylic acid (SA), jasmonic acid, and abscisic acid increased in rust-infected leaves and activated downstream signaling, with SA levels correlating closely with those of Flavan-3-ols. Pretreatment with the SA analog benzothiadiazole increased Flavan-3-ol accumulation by activating the MYB-bHLH-WD40 complex and reduced rust proliferation. Furthermore, transgenic poplar lines overproducing SA exhibited higher amounts of Flavan-3-ols constitutively via the same transcriptional activation mechanism. These findings suggest a strong association among SA, Flavan-3-ol biosynthesis, and rust resistance in poplars. Abscisic acid also promoted poplar defense against rust infection, but likely through stomatal immunity independent of Flavan-3-ols. Jasmonic acid did not confer any apparent defense responses to the fungal pathogen. We conclude that SA activates Flavan-3-ol biosynthesis in poplar against rust infection.
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Flavan 3 ols are an effective chemical defense against rust infection
Plant Physiology, 2017Co-Authors: Chhana Ullah, Sybille B Unsicker, Jonathan Gershenzon, Almuth Hammerbacher, Axel Schmidt, Christin Fellenberg, Peter C ConstabelAbstract:Phenolic secondary metabolites are often thought to protect plants against attack by microbes, but their role in defense against pathogen infection in woody plants has not been investigated comprehensively. We studied the biosynthesis, occurrence, and antifungal activity of Flavan-3-ols in black poplar (Populus nigra), which include both monomers, such as catechin, and oligomers, known as proanthocyanidins (PAs). We identified and biochemically characterized three leucoanthocyanidin reductases and two anthocyanidin reductases from P. nigra involved in catalyzing the last steps of Flavan-3-ol biosynthesis, leading to the formation of catechin [2,3-trans-(+)-Flavan-3-ol] and epicatechin [2,3-cis-(-)-Flavan-3-ol], respectively. Poplar trees that were inoculated with the biotrophic rust fungus (Melampsora larici-populina) accumulated higher amounts of catechin and PAs than uninfected trees. The de novo-synthesized catechin and PAs in the rust-infected poplar leaves accumulated significantly at the site of fungal infection in the lower epidermis. In planta concentrations of these compounds strongly inhibited rust spore germination and reduced hyphal growth. Poplar genotypes with constitutively higher levels of catechin and PAs as well as hybrid aspen (Populus tremula × Populus alba) overexpressing the MYB134 transcription factor were more resistant to rust infection. Silencing PnMYB134, on the other hand, decreased Flavan-3-ol biosynthesis and increased susceptibility to rust infection. Taken together, our data indicate that catechin and PAs are effective antifungal defenses in poplar against foliar rust infection.
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Flavan 3 ols in norway spruce biosynthesis accumulation and function in response to attack by the bark beetle associated fungus ceratocystis polonica
Plant Physiology, 2014Co-Authors: Almuth Hammerbacher, Thilo C. Fischer, Jonathan Gershenzon, Christian Paetz, Louwrance P Wright, Joerg Bohlmann, Andrew J Davis, Trevor M Fenning, Axel SchmidtAbstract:Proanthocyanidins (PAs) are common polyphenolic polymers of plants found in foliage, fruit, bark, roots, rhizomes, and seed coats that consist of Flavan-3-ol units such as 2,3-trans-(+)-catechin and 2,3-cis-(–)-epicatechin. Although the biosynthesis of Flavan-3-ols has been studied in angiosperms, little is known about their biosynthesis and ecological roles in gymnosperms. In this study, the genes encoding leucoanthocyanidin reductase, a branch point enzyme involved in the biosynthesis of 2,3-trans-(+)-Flavan-3-ols, were identified and functionally characterized in Norway spruce (Picea abies), the most widespread and economically important conifer in Europe. In addition, the accumulation of Flavan-3-ols and PAs was investigated in Norway spruce saplings after wounding or inoculation with the fungal pathogen Ceratocystis polonica, which is vectored by bark beetles (Ips typographus) and is usually present during fatal beetle attacks. Monomeric and dimeric Flavan-3-ols were analyzed by reverse-phase high-pressure liquid chromatography, while the size and subunit composition of larger PAs were characterized using a novel acid hydrolysis method and normal phase chromatography. Only Flavan-3-ol monomers with 2,3-trans stereochemistry were detected in spruce bark; dimeric and larger PAs contained Flavan-3-ols with both 2,3-trans and 2,3-cis stereochemistry. Levels of monomers as well as PAs with a higher degree of polymerization increased dramatically in spruce bark after infection by C. polonica. In accordance with their role in the biosynthesis of 2,3-trans-(+)-Flavan-3-ols, transcript abundance of Norway spruce LEUCOANTHOCYANIDIN REDUCTASE genes also increased significantly during fungal infection. Bioassays with C. polonica revealed that the levels of 2,3-trans-(+)-catechin and PAs that are produced in the tree in response to fungal infection inhibit C. polonica growth and can therefore be considered chemical defense compounds.
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the effect of milk proteins on the bioaccessibility of green tea Flavan 3 ols
Food Research International, 2014Co-Authors: Sydney Moser, Mohammad Chegeni, Owen G Jones, Andrea M Liceaga, Mario G FerruzziAbstract:Abstract While the impact of interactions between Flavan-3-ol and protein on food quality has been reported, the ability of these interactions to modify Flavan-3-ol bioavailability remains unclear. The objectives of this study were to characterize the influence of milk proteins and mineral components of the milk matrix on in vitro bioaccessibility of green tea Flavan-3-ols and to assess the relative impact of protein digestibility in the GI tract on protein-Flavan-3-ol binding. Protein solutions containing sodium-caseinate (S-CSN, 35.6 mg/mL), α-lactalbumin (α-LA, 1 mg/mL), β-lactoglobulin (β-LG, 3.5 mg/mL), or non-fat dry milk (NFDM) were prepared in Jenness Koops (JK) buffer containing milk salts and formulated at 10–40% (v/v) into green tea beverages containing 0.6 mg/mL total Flavan-3-ols. Samples were subjected to a three-stage in vitro digestion to assess Flavan-3-ol digestive release and stability (bioaccessibility). Milk protein, most notably S-CSN, significantly decreased (p
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influence of formulation and processing on absorption and metabolism of Flavan 3 ols from tea and cocoa
Annual Review of Food Science and Technology - (new in 2010), 2011Co-Authors: Andrew P Neilson, Mario G FerruzziAbstract:Flavan-3-ols are a major subclass of the class of plant phytochemicals known as flavonoids. Flavan-3-ols are commonly found in fruit, vegetable, and botanical products, including tea, cocoa, grapes, and apples. Both monomeric catechins and polymeric procyanidins are common in the diet, along with several derivatives produced by degradation of these species during processing. Both epidemiological and biological evidence suggests a health-protective role for dietary Flavan-3-ols, leading to increased interest in the bioavailability of these compounds from foods. Flavan-3-ol bioavailability depends on numerous factors, including digestive release, absorption, metabolism, and elimination. In addition to these in vivo factors, the complexity of whole-food systems (physical form, Flavan-3-ol form and dose, macronutrient and micronutrient profile, processing, etc.) influences the absorption efficiency and circulating profile of Flavan-3-ols. An understanding of how food matrices may influence Flavan-3-ol absorption will provide a framework to design and develop functional products that positively affect Flavan-3-ol absorption and, by extension, potential bioactivity.