Digestion and absorption of ferulic acid sugar esters in rat gastrointestinal tract

We estimated the absorption site and absorptivity of ferulic acid (FA) and its sugar esters, namely 5-O-feruloyl-l-arabinofuranose (FAA) and feruloyl-arabinoxylan (FAXn), in rats on the basis of their recovery in intestinal content and feces by comparing the values with those of a nonabsorbable marker, poly R-478. The results indicated that free FA was absorbed almost completely before reaching cecum. About 40% of dietary FAA was absorbed in rat foregut and 57% disappeared in the cecum. In contrast, about 67% of the FA moiety in FAXn was released and then disappeared predominantly in the hindgut. These results suggested that the existing form of FA in diets affects its absorptivity, its absorption site, and its ensuing fate in the gastrointestinal tract. Those ingested FAs esterified with saccharides; especially, polysaccharides have to transit the hindgut where FA might be released and then absorbed and/or degraded by microflora in lumen. Such microbial degradation may be an important factor affecting the bioavailability of dietary FA.     

Uptake and metabolism of hydroxycinnamic acids (chlorogenic, caffeic, and ferulic acids) by HepG2 cells as a model of the human liver

Hydroxycinnamic acids are antioxidant polyphenols common in the human diet, although their potential health benefits depend on their bioavailability. To study the hepatic uptake and metabolism, human hepatoma HepG2 cells were incubated for 2 and 18 h with caffeic, ferulic, and chlorogenic acids. Moderate uptake of caffeic and ferulic acids was observed versus a low absorption of chlorogenic acid, where esterification of the caffeic acid moiety markedly reduced its absorption. Methylation was the preferential pathway for caffeic acid metabolism, along with glucuronidation and sulfation, while ferulic acid generated glucuronides as the only metabolites. Ferulic acid appeared to be more slowly taken up and metabolized by HepG2 cells than caffeic acid, with 73% and 64% of the free, nonmetabolized molecules detected in the culture medium after 18 h, respectively. In conclusion, hydroxycinnamic acids can be metabolized by the liver as suggested by the results obtained using HepG2 cells as a hepatic model system.     

Tetramethylated dimeric procyanidins are detected in rat plasma and liver early after oral administration of synthetic oligomeric procyanidins

Procyanidins (PC) are of great interest in nutrition because they account for a major fraction of the total flavonoids ingested in Western diets and have health benefits in humans. However, it remains unknown which species of PC, namely, monomers, oligomers, or aromatic acid derivatives of gut microflora, are responsible for their beneficial effects in vivo. The high molecular complexity of PC extracts and PC-rich foods is a major problem in absorption studies. To circumvent this difficulty, we have synthesized oligomeric PC consisting of (-)-epicatechin units linked by ethyl bridges. The synthetic PC (SPC) only contains dimers, trimers, tetramers, and nanomers. After oral gavage of this SPC (200 mg/kg body weight) to male Wistar rats, tetramethylated dimeric PC (TDPC) were detected in plasma and liver. TDPC were detected in plasma as soon as 1 h after intake, reaching maximum concentrations (14 mg/L) 2 h after gavage. At this time, liver contained as much as 15 mug of TDPC per gram of tissue. In conclusion, orally administered dimeric PC are rapidly absorbed and internally methylated in rats. To our knowledge, this is the first time that methylated dimeric PC have been detected in plasma and liver. We consider that plasma and liver concentrations of TDPC are sufficient to exert a hormone-like effect and, therefore, that PC dimers are good candidates as agents of the biological activities of PC extracts and PC-rich foods.     

Intestinal distribution and excretion of sesaminol and its tetrahydrofuranoid metabolites in rats

Sesame seeds (Sesamum indicum L.) are unique because of potent and various physiological activities imparted by their bioactive lignans. This investigation studied the intestinal distribution and excretion of sesaminol in Sprague-Dawley (SD) rats. To investigate the distribution of sesaminol (per oral 220 mg/kg), the changes in concentration of sesaminol and its metabolites were determined in the intestines and plasma within the 24 h period after tube feeding of sesaminol to SD rats. Results show that the epimerization of sesaminol appeared to be catalyzed by acid in the simulated gastric fluids. The major sesaminol epimer was characterized as 2-episesaminol using 2D-NMR. These findings indicate that sesame sesaminol and its epimer are poorly absorbed prior to reaching the rectum and that substantial amounts pass from the small to the large intestine, where they are metabolized by the colonic microflora to tetrahydrofuranoid metabolites. Sesaminol in plasma was largely present as phase II conjugates, and the seven metabolites were detected as the 2-episesaminol, sesaminol-6-catechol, methylated sesaminol-catechol, R,R-hydroxymethylsesaminol-tetrahydrofuran, S,R-hydroxymethylsesaminol-tetrahydrofuran, enterolactone, and enterodiol. Excretions of sesaminol in urine and feces within the 24 h period were equivalent to 0.02 and 9.33% of the amount ingested, respectively.     

Antioxidant and antiulcerative properties of phenolics from Chinese quince, quince, and apple fruits

To evaluate the health benefits of Chinese quince and quince phenolics, their antioxidant properties and antiulcerative activity were investigated in comparison with apple phenolics as a reference. The strength of antioxidant activity and DPPH radical scavenging activity of these fruit phenolics varied according to different in vitro evaluation systems, whereas the antioxidative property of rat blood increased in all rats orally administered phenolics. Ferulic acid and isoferulic acid were detected as major metabolites in rats given apple phenolics, quince phenolics, and 5-caffeoylquinic acid standard. (-)-Epicatechin and its 3'-O-methyl ether could be detected in rats administered apple phenolics and (-)-epicatechin standard. In the ethanol-induced gastric ulcer, pre-administration of Chinese quince and quince phenolics suppressed the occurrence of gastric lesions in rats, whereas apple phenolics seemed to promote ulceration. The trend of myeloperoxidase activity was similar to that of the ulcer index. The results showed that Chinese quince and quince phenolics might have health benefits by acting both in blood vessels and on the gastrointestinal tract.     

Intestinal absorption of p-coumaric and gallic acids in rats after oral administration

Ferulic acid (FA) and p-coumaric acid (CA) are absorbed by the monocarboxylic acid transporter (MCT) in Caco-2 cells, although gallic acid (GA) is not. Therefore, the MCT is selective for certain phenolic acids. Absorption of orally administered CA and GA in rats was studied to obtain serum pharmacokinetic profiles and to investigate their intestinal absorption characteristics in vivo. Rats were administered 100 micromol/kg body weight of CA and GA, and blood was collected from the portal vein and abdominal artery after administration. CA, GA, and their metabolites were quantified with a highly selective and sensitive coulometric detection method using high-performance liquid chromatography-electrochemical detection. Ingested CA was rapidly absorbed in the gastrointestinal tract in an intact form. The serum concentration of intact CA in the portal vein peaked 10 min after dosing (C(max) was 165.7 micromol/L). In contrast, GA was slowly absorbed, with a t(max) for intact GA of 60 min and a C(max) of 0.71 micromol/L. The area under the curve for intact CA and GA was calculated from the serum concentration profile in the portal vein to be 2991.3 and 42.6 micromol min L(-)(1), respectively. The relative bioavailability of CA against GA was about 70. This is the first demonstration that absorption efficiency of CA is much higher than that of GA in vivo. The absorption characteristics of CA are clearly different from those of GA. These findings are in good agreement with the results obtained in vitro using a Caco-2 cell system.     

Effect of processing methods on the calcium, phosphorus, and phytic acid contents and nutritive utilization of chickpea (Cicer arietinum L.).

The effect of chickpea (Cicer arietinum L.) processing methods on the nutritive utilization of calcium and phosphorus and on phytic acid, a seed component that affects mineral utilization, was studied. Chemical and biological methods were used for nutritional determinations in growing rats. The digestive utilization of calcium from raw chickpea was adequate for growing rats; however, processing resulted in a slight decrease. The metabolic utilization of chickpea calcium was low because of the low rates of net absorption. This was reflected in the decreased calcium levels in longissimus dorsi muscle in the absence of mobilization of calcium from the femur. Soaking in acid solution followed by cooking decreased phytic acid content, suggesting that processing made part of the phytic acid phosphorus available. The absorbed phosphorus was greater than the nonphytic phosphorus supplied by the diet. The digestive utilization of phosphorus was similar in processed and raw chickpeas, despite the loss of soluble anion as a result of processing. These results may indicate the contribution of phosphorus in the form of inositol hexaphosphate-phosphorus.     

Microbial metabolites of ingested caffeic acid are absorbed by the monocarboxylic acid transporter (MCT) in intestinal Caco-2 cell monolayers

It was previously reported that m-coumaric acid, m-hydroxyphenylpropionic acid (mHPP), and 3,4-dihydroxyphenylpropionic acid (DHPP) are major metabolites of ingested caffeic acid formed by gut microflora and would be transported by the monocarboxylic acid transporter (MCT). We have directly measured their absorption characteristics in Caco-2 cells using a coulometric detection method involving HPLC-ECD. The proton-coupled directional transport of m-coumaric acid, mHPP, and DHPP was observed, and the transport was inhibited by an MCT substrate. The permeation of m-coumaric acid and mHPP was concentration-dependent and saturable: The Michaelis constant for m-coumaric acid and mHPP was 32.5 and 12.9 mM, respectively, and the maximum velocity for m-coumaric acid and mHPP was 204.3 and 91.2 nmol (min)(-1) (mg protein)(-1), respectively. By contrast, the permeation of DHPP was nonsaturable even at 30 mM and was inversely correlated with the paracellular permeability of Caco-2 cells. Our results demonstrate that these compounds are absorbed by the MCT, although DHPP is mainly permeated across Caco-2 cells via the paracellular pathway. MCT-mediated absorption of phenolic compounds per se and their colonic metabolites would exert significant impact on human health.     

Anthocyanin metabolism in rats and their distribution to digestive area, kidney, and brain

Anthocyanins are present in human diet due to their wide occurrence in fruits and beverages. They possess antioxidant activities and could be involved in several health effects. The aim of this study was to investigate anthocyanin metabolism and distribution in the digestive area organs (stomach, jejunum and liver) and kidney, as well as a target tissue (brain) in rats fed with a blackberry (Rubus fruticosus L.) anthocyanin-enriched diet for 15 days. Identification and quantification of anthocyanin metabolites was carried out by HPLC-ESI-MS-MS and HPLC-DAD, respectively. The stomach exhibited only native blackberry anthocyanins (cyanidin 3-O-glucoside and cyanidin 3-O-pentose), while in other organs (jejunum, liver, and kidney) native and methylated anthocyanins as well as conjugated anthocyanidins (cyanidin and peonidin monoglucuronides) were identified. Proportions of anthocyanin derivatives differed according to the organ considered, with the liver presenting the highest proportion of methylated forms. Jejunum and plasma also contained aglycone forms. In the brain, total anthocyanin content (blackberry anthocyanins and peonidin 3-O-glucoside) reached 0.25 +/- 0.05 nmol/g of tissue (n = 6). The urinary excretion of total anthocyanins was low (0.19 +/- 0.02% of the ingested amount). Thus, organs of the digestive area indicated a metabolic pathway of anthocyanins with enzymatic conversions (methylation and/or glucurono-conjugation). Moreover, following consumption of an anthocyanin-rich diet, anthocyanins enter the brain.     

Identification and antioxidant activity of flavonoid metabolites in plasma and urine of eriocitrin-treated rats

Eriocitrin, a flavonoid glycoside present in lemon fruit, is metabolized in vivo to a series of eriodictyol, methylated eriodictyol, 3,4-dihydroxyhydrocinnamic acid, and their conjugates. Plasma antioxidant activity increased following oral administration of aqueous eriocitrin solutions to rats. Eriocitrin metabolites were found in plasma and renal excreted urine through HPLC and LC-MS analyses. Eriocitrin was not detected in plasma and urine, but eriodictyol, homoeriodictyol, and hesperetin in their conjugated forms were detected in plasma of 4.0 h following administration of eriocitrin. In urine for 24 h, both nonconjugates and conjugates of these metabolites were detected. 3,4-Dihydroxyhydrocinnamic acid, which is metabolized from eriodictyol by intestinal bacteria, was detected in slight amounts with each form in 4.0-h plasma and 24-h urine. Eriocitrin was suggested to be metabolized by intestinal bacteria, and then eriodictyol and 3,4-dihydroxyhydrocinnamic of its metabolite were absorbed. Following administration of eriocitrin, plasma exhibited an elevated resistance effect to lipid peroxidation. Eriocitrin metabolites functioning as antioxidant agents are discussed.     

Toxicity and antioxidant activity in vitro and in vivo of two Fucus vesiculosus extracts

The consumption of seaweeds has increased in recent years. However, their adverse and beneficial effects have scarcely been studied. Two extracts from the brown seaweed Fucus vesiculosus containing 28.8% polyphenols or 18% polyphenols plus 0.0012% fucoxanthin have been obtained and studied to determine their toxicity in mice and rats and also their antioxidant activity. Both extracts were shown to lack any relevant toxic effects in an acute toxicity test following a 4 week daily treatment in rats. The extracts exhibited antioxidant activity in noncellular systems and in activated RAW 264.7 macrophages, as well as in ex vivo assays in plasma and erythrocytes, after the 4 week treatment in rats. Our ex vivo results indicated that compounds from extract 2 may be more easily absorbed and that the antioxidants in their parent or metabolized form are more active. These findings support the view that the daily consumption of F. vesiculosus extract 2 (Healsea) would have potential benefits to humans.     

Absorption of chlorogenic acid and caffeic acid in rats after oral administration

Absorption of orally administered chlorogenic acid (5-caffeoylquinic acid) and caffeic acid in rats was studied to obtain plasma pharmacokinetic profiles of their metabolites. Rats were administered 700 micromol/kg body weight of chlorogenic or caffeic acid, and blood was collected from the tail for 6 h after administration. Ingested caffeic acid was absorbed from the alimentary tract and was present in the rat blood circulation in the form of various metabolites. On the other hand, only traces of metabolites, supposedly caffeic and ferulic acids conjugates, were detected in rat plasma for 6 h after chlorogenic acid administration. Chlorogenic acid and small amounts of caffeic acid were found in the small intestine for 6 h after chlorogenic acid administration. These results suggest that chlorogenic acid is not well absorbed from the digestive tract, unlike caffeic acid, and subject to almost no structural changes to the easily absorbed forms.     

Orally administered crocetin and crocins are absorbed into blood plasma as crocetin and its glucuronide conjugates in mice

A series of crocetin glycosides (crocins) are the main pigment of the stigmas of saffron (Crocussativus L.) and the fruits of gardenia (Gardenia jasminoides Ellis). Although numerous studies have demonstrated that crocetin and crocins have a variety of biological functions, the metabolism of dietary crocetin and crocins remains unknown. In the present study, we investigated the intestinal absorption of orally administered crocetin and crocins in mice. Orally administered crocetin was rapidly absorbed into the blood circulation and was present in plasma as an intact free form and as glucuronide conjugates (crocetin-monoglucuronide and -diglucuronide). Crocetin and its glucuronide conjugates were also found in crocins-administered mouse plasma, whereas intact crocins (glycoside forms) were not detected. These results indicate that orally administered crocins are hydrolyzed to crocetin before or during intestinal absorption, and absorbed crocetin is partly metabolized to mono- and diglucuronide conjugates.     

Metal bioavailability and risk assessment from edible brown alga Laminaria japonica, using biomimetic digestion and absorption system and determination by ICP-MS

A new biomimetic digestion and absorption system, including in vitro bionic digestion and biomimetic membrane extraction, was used for the first time for the pretreatment of edible Laminaria japonica . After bionic digestion, 11 species of trace metals (V, Cr, Mn, Fe, Ni, Cu, Zn, Se, As, Cd, and Pb) in the resulting chyme were transformed into their final coordinated complexes and then absorbed by the biomembrane. Similar to the biomembrane between gastrointestinal tract and blood vessels, monolayer liposome was used for the first time as a biomembrane model. Affinity-monolayer liposome metals (AMLMs) were separated, determined by ICP-MS, and then used for the metal bioavailability assessment as the bioassimilated part. The action of gastrointestinal acidity and components (including digestive enzymes) was assessed on the basis of the concentration of AMLMs; the safe dosage and tolerable upper intake level of L. japonica for adults were proposed as 33.3 and 230.8 g/day, respectively.     

Pharmacokinetic study of caffeic and rosmarinic acids in rats after oral administration

p-Coumaric and ferulic acid are actively taken up by monocarboxylic acid transporter (MCT), whereas gallic acid, caffeic acid (CA), and rosmarinic acid (RA) are absorbed by paracellular diffusion in human intestinal Caco-2 cells, although CA has low affinity for MCT. We previously demonstrated that p-coumaric acid has a much higher absorption efficiency than gallic acid in rats, owing to the MCT-mediated absorption of p-coumaric acid in vivo (J. Agric. Food Chem. 2004, 52, 2527-2532). Here, absorption of orally administered CA and RA in rats has been studied to investigate their intestinal absorption characteristics and pharmacokinetics in vivo and to compare the results with those of p-coumaric and gallic acids obtained under identical conditions. Rats were given 100 micromol/kg body weight of CA and RA, and blood was collected from the portal vein and abdominal artery after administration. CA, RA, and their metabolites were quantified by a coulometric detection method using HPLC-ECD. The serum concentration of intact CA and RA in the portal vein peaked at 10 min after administration, with a C(max) of 11.24 micromol/L for CA and 1.36 micromol/L for RA. The area under the curve (AUC) for intact CA and RA in the portal vein was calculated from the serum concentration-time profile to be 585.0 and 60.4 micromol min L-1, respectively. The absorption efficiency of CA was about 9.7-fold higher than that of RA. Overall, the absorption efficiency of these compounds in vivo increases in the order: gallic acid = RA < CA < p-coumaric acid, which is in good agreement with results obtained in Caco-2 cells in vitro.     

Urinary and biliary metabolic patterns of chlorothalonil in germ-free and conventional rats.

The metabolic fate of chlorothalonil, a broad spectrum fungicide that is known to be metabolized via glutathione conjugation, was examined through the analysis of urine and bile metabolites. The role of digestive microflora in the metabolism of chlorothalonil was assessed by comparing the metabolic patterns in germ-free and conventional rats. Low urinary and biliary excretion of radioactivity was observed in both conventional and germ-free rats. However, the urinary excretion of radioactivity was higher in conventional than in germ-free rats. Radio-HPLC analysis of urine and bile showed a complex metabolic profile in both conventional and germ-free rats. Methylthio metabolites of chlorothalonil were determined in ethyl acetate extracts of urine and bile of conventional and germ-free rats. These metabolites were excreted in a higher amount in the urine of conventional rats than in the urine of germ-free rats. This study shows the complexity of chlorothalonil metabolism and the role of the digestive microflora in chlorothalonil metabolism.     

Hydrolysis of Chicoric and Caftaric Acids with Esterases and Lactobacillus johnsonii in Vitro and in a Gastrointestinal Model

Chicoric acid (ChA) and caftaric acid (CafA) were identified as bioactive components of chicory and have been ascribed a number of health benefits. This study investigated the hydrolysis of ChA and CafA with enzymes and a probiotic bacterium Lactobacillus johnsonii (La1). Esterase from Aspergillus japonicus (24 U/mg) hydrolyzed 100% of ChA (5 mM) and CafA (5 mM) after 3 h, at pH 7.0 and 37 °C. Under the same reaction conditions, 100% hydrolysis of ChA and CafA was achieved with a spray-dried preparation of La1. The addition of La1 (100 mg/mL, 3.3 E9 cfu/g) to CafA solution in a gastrointestinal model (GI model) resulted in 65% hydrolysis of CafA. This model simulates the physicochemical conditions of the human gastrointestinal tract. No hydrolysis of CafA was observed after passage through the GI model in the absence of La1. The results of this study support the hypothesis that ChA and CafA are degraded by gut microflora before absorption and metabolization.     

果胶对脂类和类胡萝卜素消化利用影响研究进展

果胶已经被证实可以影响脂类的消化,脂溶性的类胡萝卜素在消化阶段需要被脂滴包裹才能进入小肠形成胶束,因此果胶对类胡萝卜素的消化利用也会存在潜在影响。该文综述了近年来果胶对脂类和类胡萝卜素消化利用影响研究进展,主要分为果胶对消化液黏度的影响、对消化酶的影响、与钙离子的相互作用、与胆盐的结合作用以及对脂滴的包裹作用这5个方面。该文为后续分析如何提高果蔬中类胡萝卜素生物利用度提供理论依据。     

Ingested delphinidin-3-rutinoside is primarily excreted to urine as the intact form and to bile as the methylated form in rats

Many reports have described the bioavailability of anthocyanins; however, most of these reports investigated only the amount of anthocyanins excreted in urine. In the present study, we calculated the pharmacokinetic bioavailability of anthocyanins in rats by measuring the plasma concentration of delphinidin-3-rutinoside that had been administered orally or intravenously. Delphinidin-3-rutinoside was primarily absorbed in the blood and excreted into urine as unmetabolized forms with a T(max) of 26.3 min and a C(max) of 0.285 +/- 0.071 micromol/L. We detected small amounts of the metabolite 4'-O-methyl-delphinidin-3-rutinoside in the plasma, but we detected neither anthocyanidin (aglycone) nor glucuro- or sulfoconjugates. For the 8 h period after intake, delphinidin-3-rutinoside and 4'-O-methyl-delphinidin-3-rutinoside were excreted to urine at 795 +/- 375 and 12.3 +/- 2.91 nmol, respectively. Relative to intravenous injection, oral administration of delphinidin-3-rutinoside resulted in complete bioavailability (0.49 +/- 0.06%). Analysis of delphinidin-3-rutinoside plasma concentrations in bile cannulated rats revealed that, for the 8-h period after intake, the intact delphinidin-3-rutinoside excretion ratio in bile was 11% of the excretion ratio of 4'-O-methyl-delphinidin-3-rutinoside, 1.91 +/- 0.35 nmol versus 17.4 +/- 8.67 nmol, respectively. Setting the bile duct cannulation in a Bollman-type cage, however, significantly increased the bioavailability of orally administered delphinidin-3-rutinoside (18.14 +/- 6.24%). This effect appears to stem immobilization stress by reducing gastrointestinal motility. The cumulative excretion of delphinidin-3-rutinoside and 4'-O-methyl-delphinidin-3-rutinoside in urine and bile was 2.67 +/- 1.24% (w/w) of the dose ingested. Studies report that several metabolites are formed after oral ingestion of anthocyanins. Examples include glucuronyl from cyanidin-3-glucoside and both glucuronyl and sulfate conjugates from pelargonidin-3-glucoside. Our results indicate that delphinidin-3-rutinoside might be metabolized differently from cyanidin-3-glucoside and pelargonidin-3-glucoside.     

Transepithelial transport of chlorogenic acid, caffeic acid, and their colonic metabolites in intestinal caco-2 cell monolayers

Both chlorogenic and caffeic acids exhibited nonsaturable transport in Caco-2 cells, whereas caffeic acid also showed proton-coupled polarized absorption. Thus, the absorption efficiency of caffeic acid was greater than that of chlorogenic acid. Polarized transport of caffeic acid was inhibited by substrates of MCT such as benzoic and acetic acids. Almost all of the apically loaded chlorogenic and caffeic acid was retained on the apical side, and the transepithelial flux was inversely correlated with the paracellular permeability of Caco-2 cells. These results indicate that transport was mainly via paracellular diffusion, although caffeic acid was absorbed to a lesser extent by the monocarboxylic acid transporter (MCT). Furthermore, m-coumaric acid and 3-(m-hydroxyphenyl)propionic acid, the main metabolites of chlorogenic and caffeic acid by colonic microflora, competitively inhibited the transport of fluorescein, a known substrate of MCT. This suggests that their absorption could also be mediated by MCT. These findings have exemplified the physiological importance of MCT-mediated absorption in both phenolic acids per se and their colonic metabolites.