Bioavailability Of Catechins Research Articles

Systemic Absorption of Catechins after Intraruminal or Intraduodenal Application of a Green Tea Extract in Cows.

Green tea catechins have various potential health benefits in humans including anti-inflammatory, anti-oxidative and hepato-protective effects. If present in the circulation, they might have similar effects in ruminants, which are exposed to oxidative stress and fatty liver disease such as dairy cows during the periparturient phase. However, the bioavailability of a substance is a prerequisite for any post absorptive effect in vivo. This study aimed to investigate the appearance of catechins from a green tea extract (GTE) in cattle plasma after intraruminal and intraduodenal administration because absorption is of major importance regarding the bioavailability of catechins. The studies were performed in 5 rumen-fistulated non-lactating heifers and 6 duodenally fistulated lactating dairy cows, respectively, equipped with indwelling catheters placed in a jugular vein. The GTE was applied intraruminally (10 and 50 mg/kg BW, heifers) or duodenally (10, 20 and 30 mg/kg BW, dairy cows) in a cross‐over design with a 2 d washout period between different dosages. Blood samples were drawn following the GTE administration at various pre-defined time intervals. The concentration of the major GTE catechins (gallocatechin, epigallocatechin, catechin, epicatechin, epigallocatechin-gallate, epicatechin-gallate) in plasma samples were analysed by HPLC with electrochemical detection. Irrespective of the dose, almost none of the catechins originally contained in the GTE were detected in plasma samples after intraruminal application. In contrast, intraduodenal administration of GTE resulted in increased plasma concentrations of epicatechin, epigallocatechin, epigallocatechin gallate in a dose‐dependent manner. Thus, we can conclude that intraruminally or orally administered catechins are intensively metabolized by ruminal microorganisms.

Enhancement of photoprotection potential of catechin loaded nanoemulsion gel against UVA induced oxidative stress

The present study was aimed to develop a catechin (CA) loaded nanoemulsion based nano-gel for the protection of skin against ultraviolet radiation (UV) induced photo-damage and to ensure its enhanced skin permeability as well as bioavailability through transdermal route. The optimized nanoemulsion (CA-NE4) was prepared by spontaneous nano-emulsification method. It was composed of oil (ethyl oleate), Smix [surfactant (span 80) and co-surfactant (transcutol CG)] and aqueous system in an appropriate ratio of 15:62:23% w/w respectively. The CA-NE4 was characterized through assessment of droplet size, zeta potential, refractive index, transmission electron microscopy (TEM), UV, high performance thin layer chromatography (HPTLC) and Fourier transform infrared spectroscopy (FTIR) analysis. The average droplet size and zeta potential of CA-NE4 were found to be 98.6±1.01nm and −27.3±0.20mV respectively. The enhanced skin permeability was better with CA-NE4 based nano-gel (CA-NG4) [96.62%] compared to conventional gel (CA-CG) [53.01%] for a period of 24h. The enhanced % relative bioavailability (F) of CA (894.73), Cmax (93.79±6.19ngmL−1), AUC0−t∞ (2653.99±515.02nghmL−1) and Tmax (12.05±0.02h) was significantly obtained with CA-NG4 as compared to oral suspension for extended periods (72h). CA-NG4 could improve the level of cutaneous antioxidant enzymes like superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) and reduce the level of thiobarbituric acid reactive substances (TBRAS) against oxidative stress induced by UVA. Nano-gel formulation of CA showed sustained release profile and enhanced photoprotection potential due to its improved permeability as well as bioavailability (P<0.05) compared to the conventional gel. Therefore, transdermal administration of nano-gel (CA-NG4) of CA offers a better way to develop the endogenous cutaneous protection system and thus could be an effective strategy for decreasing UV-induced oxidative damage in the skin tissues.

Bioavailability of catechins from guaraná (Paullinia cupana) and its effect on antioxidant enzymes and other oxidative stress markers in healthy human subjects

We assessed the effects of guaraná (Paullinia cupana) consumption on plasma catechins, erythrocyte antioxidant enzyme activity (superoxide dismutase, catalase and glutathione peroxidase) and biomarkers of oxidative stress (ex vivo LDL oxidation, plasma total antioxidant status and ORAC, and lymphocyte single cell gel electrophoresis) in healthy overweight subjects. Twelve participants completed a 15-day run-in period followed by a 15-day intervention with a daily intake of 3 g guaraná seed powder containing 90 mg (+)-catechin and 60 mg (-)-epicatechin. Blood samples were taken on the first and last day of the intervention period, fasting and 1 h post-dose. The administration of guaraná increased plasma ORAC, while reducing ex vivo LDL oxidation (only in the first study day) and hydrogen peroxide-induced DNA damage in lymphocytes, at 1 h post-dose. Plasma catechin (0.38 ± 0.12 and 0.44 ± 0.18 nmol mL(-1)), epicatechin (0.59 ± 0.18 and 0.64 ± 0.25 nmol mL(-1)) and their methylated metabolites were observed at 1 h post-dose but were almost negligible after overnight fasting. The activities of catalase (in both study days) and glutathione peroxidase (in the last intervention day) increased at 1 h post-dose. Furthermore, the activity of both enzymes remained higher than the basal levels in overnight-fasting individuals on the last intervention day, suggesting a prolonged effect of guaraná that continues even after plasma catechin clearance. In conclusion, guaraná catechins are bioavailable and contribute to reduce the oxidative stress of clinically healthy individuals, by direct antioxidant action of the absorbed phytochemicals and up-regulation of antioxidant/detoxifying enzymes.

Capsule Formats May Hamper Green Tea Catechin Bioavailability

Capsule Formats May Hamper Green Tea Catechin Bioavailability

Improved stability of (+)-catechin and (−)-epicatechin by complexing with hydroxypropyl-β-cyclodextrin: Effect of pH, temperature and configuration

The stability and bioavailability of catechins, a kind of tea polyphenols with health benefit, could be improved by complexing with cyclodextrins. The aim of this study was to investigate the complexation of two geometrical isomers, (+)-catechin and (−)-epicatechin, with hydroxypropyl-β-cyclodextrin (HP-β-CD) in tris–HCl buffer solutions at pH 6.8–8.0 using isothermal titration calorimetry, fluorescence and proton nuclear magnetic resonance spectroscopy. Experimental results showed that these inclusion interactions are primarily enthalpy-driven processes. The complexation constant (KC) of EC+HP-β-CD complex was less than that of CA+HP-β-CD at the same temperature and pH value. Temperature and pH studies showed that the KC value decreased with the rise of temperature and pH. Stability study indicated that HP-β-CD showed a stronger protection effect on CA than that on EC. The different inclusion modes between CA and EC were discussed in terms of the discrepancy in their molecular structures.

Green Tea Formulations with Vitamin C and Xylitol on Enhanced Intestinal Transport of Green Tea Catechins

The effect of green tea formulated with vitamin C and xylitol on intestinal cell transport of gallated and nongallated catechin was studied. The transport of catechins from both apical to basolateral and basolateral to apical directions was measured. The effect of vitamin C (4, 10, 20 ppm), xylitol (11, 27.5, 55 ppm), and combinations of both on the intestinal transport rate of catechins was examined. The efflux value (Pb→a/Pa→b) of (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), (-)-epicatechin (EC), and (-)-epicatechin gallate (ECG) was 0.26, 0.22, 1.22, and 0.17, respectively, indicating that EC appeared to be less absorbed compared with other catechins. The addition of xylitol (11, 27.5, 55 ppm) and vitamin C (4, 10, 20 ppm) and in combination enhanced transport rate of nongallated catechins such as EC and EGC. For EC, vitamin C was revealed to be the most effective on intestinal transport, implying the inhibition of the efflux transport mechanism of EC. Intestinal transport of gallated catechins significantly increased from catechins formulated with vitamin C and xylitol in a dose-dependent manner compared to the catechin-only formulation. Results provide a potential strategy to enhance the delivery and bioavailability of catechins in humans by modulating green tea formulation with vitamin C and xylitol.

Influence of Gallate and Pyrogallol Moieties on the Intestinal Absorption of (−)‐Epicatechin and (−)‐Epicatechin Gallate

The cellular accumulation of individual catechins was measured as an index of intestinal absorption to clarify the interactions among catechins. The cellular accumulation of (-)-epicatechin (EC) increased in the presence of other catechins. The ability of gallate catechin such as (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin gallate (ECG) to increase the cellular accumulation of EC was greater than that of nongallate catechins. Gallic acid octyl ester (GAO) also increased the cellular accumulation of EC by 426% as compared with that in untreated cells. Conversely, the cellular accumulation of ECG was not influenced by other catechins, but it increased by 54% in the presence of GAO. Experiments using GAO derivatives indicated that the gallate moiety required the presence of a catechol group and a neighboring carbonyl group, whereas the pyrogallol moiety, without a neighboring carbonyl group, required 3 hydroxyl groups to increase the cellular accumulation of EC. Furthermore, gallate esters required long carbon chains to increase the same. The experiment using EGCG, GAO, or their derivatives indicated that the ability of gallate or pyrogallol moiety to increase the cellular accumulation of EC was restricted by their hydrophobicity. These results suggest that the co-administration of foods containing functional materials such as gallate or pyrogallol moieties, increases the intestinal absorption of catechin. The cellular accumulation of (-)-epicatechin increased by the gallate or pyrogallol moiety in catechin structure. The interaction among catechins appeared to affect intestinal absorption of catechin. The bioavailability of catechin may be improved by co-administration of functional foods.

Milk enhances intestinal absorption of green tea catechins in in vitro digestion/Caco-2 cells model

The effect of milk on the absorption of polyphenols is still controversial so far. In order to determine the impact of milk addition on green tea catechins bioaccessibility and intestinal absorption an in vitro digestion/Caco-2 cell model was applied. Green tea extract (GTE) was solubilized in distilled water at 23°C and 100°C, combined with skimmed milk (GTE+10% milk and GTE+25% milk) and subjected to simulated gastric and intestinal digestion, followed by transepithelial absorption in Caco-2 cells monolayers. In the mixture with milk, gallated catechins: ECG and EGCG showed binding to milk proteins while EC and EGC seemed to have weaker affinity. Catechins were stable during gastric incubation and very sensitive to intestinal digestion. Bioaccessibility of green tea catechins brewed at 100°C was higher than brewed at 23°C. Catechins from digested GTE with 10% and 25% milk exhibited enhanced intestinal permeability in Caco-2 model in comparison to non-digested GTE and digested GTE without milk. Apparent permeability coefficients (Papp) of EGCG and ECG in digested GTE with 25% milk were significantly higher compared to those in GTE with 10% milk, and amounted to 2.41×10−6cm/s and 1.39×10−6cm/s. The recoveries of all catechins in GTE with milk in Caco-2 cells after 2h incubation were significantly higher than that without milk. To summarize, these data suggest that milk addition may increase catechin bioavailability by enhancing their transepithelial absorption and uptake from green tea extract.

Dose response bioavailability of green tea catechins in humans

Tea is an infusion of the leaves of the Camellia sinensis plant and is the most widely consumed beverage in the world after water. Because the bioavailability of green tea catechins appears to be simpler than other polyphenols, studies on catechin bioavailability have provided precise data. However, not all is known on this topic. We investigated dose response plasma appearance of catechins after ingestion of increasing doses of commercially available infused green tea by 10 healthy volunteers.Regardless of the dose, EGC and EC were the most abundant plasmatic metabolites.Area under the curve (AUC) of EGCg and EC increased with the ingested dose of the beverage. On the other hand, the AUC of EGC and 4‐O‐Me‐EGC showed a dose response effect between the low and medium dose ingested, but saturation occurred between the medium and high doses drunk. Finally the AUC of ECg decreased with the ingested dose. The same findings were observed for Cmax. While the sum of AUC per dose showed an overall saturation effect between the medium and high dose of green tea ingested, one should be careful in interpreting the data, as the pattern of individual catechins absorption differs from one another.

Enhancement of catechin skin permeation via a newly fabricated mPEG-PCL-graft-2-hydroxycellulose membrane

Green tea extracts largely consist of anti-oxidative/anti-inflammatory catechins such as (−)-epigallocatechin gallate. Orally administered catechins are metabolized in the gastrointestinal tract and liver, subsequently incurring low bioavailability. This study attempts to improve the bioavailability of catechin by using mPEG-PCL-graft-2-hydroxycellulose (mPEG-PCL-g-HEC) porous membrane as a penetration matrix for skin delivery of catechins. The green tea-extracted catechin was obtained based on the partition difference in two phases of solvents. In vitro permeation tests using a Franz diffusion cell system indicated that the mPEG-PCL-g-HEC membrane with a loading content of the catechins of 1.5mg/cm2 significantly enhanced the permeation of the catechins up to 0.84mg/mL in the receptor of Franz cell for a period of 48h, whereas the permeated catechins through HEC membrane was only 0.04mg/mL. Moreover, a comparative experiment of the oral and transdermal administrations was conducted to measure the delivered catechins in plasma in Wistar rats. In the oral administration where free catechin was given, the catechin AUC was 34.22±1.51μgh/mL and Cmax was 22.7±1.29μg/mL, respectively. Conversely, in the transdermal administration using catechins-loaded E50C36-g-HEC membranes, the catechin AUC of 356.24±3.24μgh/mL and Cmax of 19.03±0.75μg/mL was obtained. Furthermore, a higher catechin AUC of E50C36-g-HEC membrane than that of E50-C84-g-HEC membrane presented a role of the permeation enhancer to the amphiphilic polymer grafted to the cellulosic material. Therefore, this study showed the potential use of amphiphilic polymer mPEG-PCL in controlling the delivery of catechins via skin.

Increased Plasma Concentration of Epigallocatechin in Mice after Orally Administering a Green Tea (Camellia sinensisL.) Extract Supplemented by Steamed Rice

We attempted to improve the bioavailability of green tea catechins by using food ingredients. The catechin bioavailability of a green tea extract administered to mice was significantly (p<0.05) increased by supplementing with steamed rice. This enhanced bioavailability was due to the increased concentration of plasma non-gallated catechins, especially epigallocatechin (EGC).

Chocolate Matrix Factors Modulate the Pharmacokinetic Behavior of Cocoa Flavan-3-ol Phase II Metabolites Following Oral Consumption by Sprague−Dawley Rats

The impact of carbohydrates and milk on the bioavailability of catechin (C) and epicatechin (EC) from chocolate has been previously studied. However, little data exist regarding potential modulation of the phase II metabolism by these chocolate matrix factors. The objectives of this study were to assess the impact of matrix composition on qualitative and quantitative profiles of circulating catechins and their metabolites following administration of commercially relevant chocolate confections. Sprague-Dawley rats were administered 1.5 g of a confection (reference dark, high sucrose, or milk chocolate) by intragastric gavage, and plasma samples were collected over 8 h. High-performance liquid chromatography-mass spectrometry analysis was performed to quantify C, EC, and their metabolites. The predominant metabolites were O-glucuronides (two metabolites) and O-Me-O-glucuronides (three metabolites). Plasma concentrations of metabolites were generally the highest for high sucrose treatment and lowest for milk treatment, while the reference dark treatment generally resulted in intermediate concentrations. The O-Me-(+/-)-C/EC-O-beta-glucuronide (peak 4) was significantly higher for the high sucrose treatment (2325 nM h) versus the milk treatment (1300 nM h). Additionally, C(MAX) values for (+/-)-C/EC-O-beta-glucuronide (peak 3) and two O-Me-(+/-)-C/EC-O-beta-glucuronides (peaks 4 and 6) were significantly higher for the high sucrose treatment (4012, 518, and 2518 nM, respectively) versus the milk treatment (2590, 240, and 1670 nM, respectively). Milk and sucrose appear to modulate both metabolism and plasma pharmacokinetics and, to a lesser extent, the overall bioavailability of catechins from chocolate confections.

Bioadhesive chitosan nanoparticles: Preparation and characterization

Bioadhesive chitosan nanoparticles (CS NPs) were prepared for encapsulation of catechin and evaluation of their mucoadhesive potential that leads to enhanced oral bioavailability of catechin. CS NPs and catechin loaded CS NPs were obtained by ionic gelation between the CS and sodium tripolyphosphate (TPP). Particle size distribution analysis confirmed the size ranges, 110 ± 5 nm and 130 ± 5 nm for CS NPs and catechin loaded CS NPs, respectively. TEM indicated smooth and spherical nanoparticles. FTIR and DSC showed no significant interactions between catechin and CS after encapsulation and cross-linking. Entrapment efficiency of 90% was achieved with a weight ratio of 2:1 (CS:TPP) at pH 5.5. In vitro release of catechin from CS NPs was 32% within 24 h and exhibited 40% and 32% mucoadhesivity for catechin loaded CS NPs and CS NPs, respectively, demonstrating potential for controlled release of catechin in GIT.

Bioavailability of catechins from ready-to-drink tea

Objective Because 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. Methods A 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. Results Eight 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. Conclusions The 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.

Formulation with ascorbic acid and sucrose modulates catechin bioavailability from green tea

In order to investigate the impact of common food ingredients on catechin absorption, green tea (GT) extract (50 mg) was formulated plain, with sucrose (GT+S), with ascorbic acid (GT+AA) and with sucrose and ascorbic acid (GT+S+AA). Bioavailability and bioaccessibility were assessed in Sprague Dawley rats and an in vitro digestion/Caco-2 cell model respectively. Absorption of epigallocatechin (EGC) and epigallocatechin gallate (EGCG) was significantly (P<0.05) enhanced in GT+S+AA formulations (AUC(0-6h)= 3237.0 and 181.8 pmol*h/L plasma respectively) relative to GT control (AUC(0-6h) = 1304.1 and 61.0 pmol*h/L plasma respectively). In vitro digestive recovery was higher for EGC and epicatechin (EC) (∼51-53%) relative to EGCG and epicatechin gallate (ECG) (< 20%) and was modestly enhanced in GT+S and GT+S+AA formulations. Accumulation of EGC, EGCG and ECG by Caco-2 cells was significantly (P<0.05) higher from GT+S+AA compared to other formulations while retention of catechins was enhanced in presence of ascorbic acid. These data suggest that formulation with sucrose and ascorbic acid may improve catechin bioavailability by enhancing bioaccessibility and intestinal uptake from tea.

Influence of chocolate formulation factors on in vitro bioaccessibility and bioavailability of catechins in humans

Conflicting data exist regarding the effect of carbohydrate and milk on bioavailability of catechins from chocolate. To test the effects of these ingredients, solid [reference dark (SD), high sucrose (SHS), high milk solids (SMS)] and beverage [high sucrose (LHS), artificial sweetener (LAS)] chocolate products providing physiologically relevant levels of epicatechin (EC, 30 mg/serving) were formulated. Subjects (n=6) consumed one serving of chocolate, and serum pharmacokinetics were monitored for 6 h. Subjects consumed all 5 products in a crossover design. Plasma Cmax and AUC0‐6h of EC from SMS samples were not significantly different from the reference SD chocolate, but were significantly lower than SHS as well as both beverages. Plasma Cmax of EC from the LHS beverage was also significantly higher than the reference SD chocolate. Recovery of EC through in vitro digestion (bioaccessibility) did not differ between formulations. Furthermore, EC accumulation by Caco‐2 intestinal cells exposed to in vitro digesta from each product for 1 h were not significantly different, but retention of EC over 1 h was significantly greater in cells exposed to digesta from SMS product than other solid products. These data suggest that gastric emptying and intestinal cell retention are the main mechanisms by which formulation factors may alter the pharmacokinetic properties of catechins from chocolate. Supported by Kraft Foods.Grant Funding SourceKraft Foods Global

Exposure and toxicity of green tea polyphenols in fasted and non-fasted dogs

Standardized green tea extract was evaluated for exposure and toxicity in Beagle dogs following oral dosing by capsules. The main component (−)-epigallocatechin gallate (EGCG) accounted for 56–72% of the material. A 9-month chronic study (0, 200, 500, and 1000mg/kg/day) was done in fasted dogs to take advantage of the reported improved catechin bioavailability with fasting. Extensive morbidity, mortality, and pathology of many major organs led to its early termination at 6.5 months and prevented identification of the toxicity mechanisms. A follow-up 13-week study examined the exposure to and toxicity of the extract. In general, toxicities were less severe than in the chronic study during the same interval. Dosing in a fed state resulted in considerably lower and less variable exposure than found under fasted conditions. Toxicity was less frequent and of lesser severity with lower exposure but limited sample size and large variability prevented reaching that definitive conclusion. Differences in mortality and morbidity between the preliminary terminated chronic and follow-up subchronic studies with the same dose of the same drug lot and similar exposure were not fully resolved as there may be other as yet unclear confounding factors.

Green tea formulation modulates catechin in vitro bioaccessibility and bioavailability in Sprague‐Dawley rats

To characterize the impact of green tea formulation on catechin bioavailability, 50 mg of green tea (GT) extract providing 3.8, 1.8, 1.5, and 2.5 micromoles of epicatechin (EC), epigallocatechin (EGC), epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) respectively was formulated plain (GT), with sucrose (GTS, 1.3g), and with sucrose plus ascorbic acid (GTS+AA, 10mg). Catechin digestive stability and intestinal uptake were assessed using a coupled in vitro digestion/Caco‐2 cell model. In vivo bioavailability was investigated in Sprague Dawley rats by 6h oral pharmacokinetic (PK) study. Catechin levels were measured by RPC18 HPLC. Addition of AA significantly (p&lt;0.05) increased catechin in vitro digestive recovery (20 to &gt;75%) with greatest impact on EGC (5 to &gt;90%) and EGCG (6 to &gt;61%). Caco‐2 intracellular accumulation of EGC was significantly increased to 70 pmol/mg protein by formulation with AA, compared to undetectable levels in GTS formulations. In vivo plasma PK data suggest that bioavailability of digestively labile EGCG and EGC may be enhanced by formulation with AA (AUC= 310 and 2671 nmol/mL respectively) relative to controls (AUC = 195 and 2346 nmol/L respectively). These data provide evidence that formulation factors impact both digestive recovery and may influence intestinal absorption of catechins from tea beverages in vivo. (Supported by NIH NCCAM grant P50‐AT00477)

Sorghum Extrusion Increases Bioavailability of Catechins in Weanling Pigs

Catechins and procyanidins are beneficial for human health; however, their bioavailability is low. The effect of food processing on catechin bioavailability from sources containing predominantly procyanidins has not been studied. The sumac sorghum mixture (50% whole grain+50% bran) used in this study contained catechins, procyanidins dimers, and polymers at 0.08, 0.6, and 26.4 mg/g, respectively. Extrusion decreased the polymeric procyanidins by 48% to 22 mg/g while increasing catechins (50%) and dimers (64%) to 0.12 and 1.0 mg/g, respectively. Six weanling pigs (8.9+/-1.1 kg) received a single dose by gavage of the sorghum mixture (7 g/kg0.75), the sorghum mixture extrudate, or white sorghum (50% whole grain+50% bran) in a randomized crossover design. Treatments were separated by a 7-day washout period. Blood was drawn at 0, 1, 2, and 4 h. Plasma catechin, 3'-O-methylcatechin, 4'-O-methylcatechin, epicatechin, 3'-O-methylepicatechin, and 4'-O-methylepicatechin peaked at 1 h and were 18, 43, 1, 0.7, 0.7, and 0.3 nmol/L for pigs receiving sorghum, respectively. Plasma levels in pigs receiving extruded sorghum were 66, 110, 2, 16, 8, and 11 nmol/L, respectively. Plasma levels of catechin, 3'-O-methylcatechin, and the total catechins were higher in pigs fed extruded sorghum at 1, 2, and 4 h postdose (P<or=0.05). The majority of the absorbed catechins were excreted within 4 h after feeding. Urinary excretion of total catechins was significantly higher in pigs fed extruded sorghum than in those fed nonextruded sorghum. Procyanidin dimers were not detected in plasma or urine. The levels of catechins were close to zero in plasma and urine of pigs fed white sorghum. In conclusion, extrusion improved the bioavailability of catechins in sorghum.

(+)-Catechin is more bioavailable than (−)-catechin: Relevance to the bioavailability of catechin from cocoa

Catechin is a flavonoid present in fruits, wine and cocoa products. Most foods contain the (+)-enantiomer of catechin but chocolate mainly contains ( − )-catechin, in addition to its major flavanol, ( − )-epicatechin. Previous studies have shown poor bioavailability of catechin when consumed in chocolate. We compared the absorption of ( − ) and (+)-catechin after in situ perfusion of 10, 30 or 50 μmol/l of each catechin enantiomer in the jejunum and ileum in the rat. We also assayed 23 samples of chocolate for (+) and ( − )-catechin. Samples were analyzed using HPLC with a Cyclobond I-2000 RSP chiral column. At all concentrations studied, the intestinal absorption of ( − )-catechin was lower than the intestinal absorption of (+)-catechin (p < 0.01). Plasma concentrations of ( − )-catechin were significantly reduced compared to (+)-catechin (p < 0.05). The mean concentration of ( − )-catechin in chocolate was 218 ± 126 mg/kg compared to 25 ± 15 mg/kg (+)-catechin. Our findings provide an explanation for the poor bioavailability of catechin when consumed in chocolate or other cocoa containing products.