QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Adam, A. Articles by Rémésy, C. Search for Related Content PubMed PubMed Citation Articles by Adam, A. Articles by Rémésy, C.

---

Nutrient Metabolism

The Bioavailability of Ferulic Acid Is Governed Primarily by the Food Matrix Rather than Its Metabolism in Intestine and Liver in Rats¹

Institut Technique des Céréales et des Fourrages (ITCF), Laboratoire Qualité des Céréales, 75013 Paris, France and ^* Laboratoire Maladies Métaboliques et Micronutriments, Centre de Recherches en Nutrition Humaine Auvergne, I.N.R.A. Clermond-Ferrand/Theix, F-63122 St-Genès-Champanelle, France

²To whom correspondence should be addressed. E-mail: aadam{at}clermont.inra.fr.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
The physiologic importance of ferulic acid (FA), and notably its antioxidant properties, depends upon its availability for absorption and subsequent interaction with target tissues. Because FA is widely present in cereals, the aim of the present study was to investigate its intestinal and hepatic metabolism in rats by in situ intestinal perfusion model (from 10 to 50 nmol/min), and its bioavailability in supplemented diets (from 10 to 250 µmol/d) or in a complex cereal matrix, i.e., whole flours from Valoris (Triticum aestivum) or Duriac (T. durum) cultivars and bran or white flour from the Valoris cultivar. In perfused rat intestine, net FA absorption was proportional to the perfused dose (R² = 0.997); once absorbed, FA was completely recovered as conjugated forms in plasma and bile secretion (representing 5–7% of the perfused dose). In rats fed FA-enriched semipurified diets, FA absorption was quite efficient because 50% of the ingested dose was recovered in urine. This extensive elimination by kidneys limited FA accumulation in plasma (typically 1 µmol/L in rats fed 50 µmol FA/d). In contrast, in rats fed cereal diets providing 56–81 µmol FA/d, urine excretion was 90–95% lower than in rats fed FA-enriched semipurified diets, and plasma concentrations were 0.2–0.3 µmol/L. Thus, the cereal matrix appears to severely limit FA bioavailability. This inherently low bioavailability of FA in cereals likely reflects FA association with the fiber fraction through cross-linking with arabinoxylans and lignins.

KEY WORDS: • ferulic acid • bioavailability • absorption • cereals • rats

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Prospective studies have found that the habitual intake of whole-grain foods is associated with reduced coronary heart disease, total cancer mortality (1 ,2 ), incidence of diabetes (3 ) and coronary heart disease mortality (4 –7 ). More specifically, intake of dietary fiber, especially from grain sources, has also been linked to reduced risk of coronary heart disease (8 ) and diabetes (3 ). Whole-grain foods contain a variety of biologically active constituents such as vitamin B, vitamin E, selenium, zinc, copper, magnesium and phytochemicals such as phenolic compounds, which may contribute synergistically to the health effects of plant foods (9 ). Hydroxycinnamic acid derivatives such as p-coumaric and ferulic acid are present in cereal cell walls; ferulic acid (FA)³ is the most common phenolic acid in monocotyledonous cell walls (10 ). In wheat, this acid is ester-linked to position O-5 of the arabinosyl side chains of cell wall arabinoxylans, and occurs in high concentrations in the aleurone, pericarp and embryo cells walls, but only in trace amounts in the starchy endosperm of ripe kernels (11 ). The trans-isomer predominates and accounts for 90% of the total phenolic acids in common flour (12 ). There was a very high genetic variability in the ferulic acid contents of the durum wheat varieties studied. The concentrations ranged from 0.7 to 2.4 mg/g dry matter, and the levels were higher than those reported for common wheat, which varies from 0.5 to 1 mg/g dry matter (13 ). Thus, regular consumption of whole cereals, for example whole bread, may result in ingestion of large amounts of ferulic acid.

Ferulic acid has a high antioxidant potential due to its resonance-stabilized phenoxy radical structure. It is an effective scavenger of free radicals and it has been approved in certain countries as a food additive to prevent lipid peroxidation (14 ). In vitro, it also protects LDL from metmyoglobin-induced oxidative damage (15 ). A large proportion of ferulate dimers are present in a range of plant materials, notably in wheat bran (5–8-BendiFA, 8-O-4-diFA and 5–5-diFA). In vitro, the antioxidant properties of two chemically synthesized ferulate dimers, 5–5-diFA and 5–8-BendiFA, have been documented (16 ). In the aqueous phase, both dimers were less effective antioxidants than ferulic acid, although they were more efficient at inhibiting lipid peroxidation. Moreover, FA as a free acid had less suppressive effect on LDL oxidation than ferulic acid sugar esters (feruloyl arabinose) (17 ).

The physiologic importance of FA, and notably its antioxidant property, depends upon its availability for absorption and subsequent interaction with target tissues. Therefore, it is important to estimate the bioavailability of this compound to appreciate more fully its real physiologic effect. Very few studies have been undertaken concerning the uptake of FA from the diet. Choudhury et al. (18 ) showed in rats that 10% of the FA ingested was recovered in urine 24 h after the beginning of gavage, and this urinary excretion was on the same order as that of humans who had consumed tomatoes (19 ).

Because FA is widely present in cereals, the aim of the present study was to investigate in rats first its intestinal and hepatic metabolism by an in situ intestinal perfusion model (from 10 to 50 nmol/min), and then its bioavailability in supplemented diets (from 10 to 250 µmol/d) compared with those in a complex cereal matrix.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Chemicals.

Ferulic acid was purchased from Extrasynthese (Genay, France). ß-Glucuronidase/sulfatase from Helix pomatia were purchased from Sigma (L’Isle D’Abeau, Chesnes, France). Mineral (AIN 93M) and vitamin (AIN 76A) mixes incorporated into the diets for the intestinal perfusion experiment were purchased from ICN (Orcay, France).

Whole wheat flour and milled fractions.

Valoris was provided by ITCF (Institut Technique des Céréales et des Fourrages, Paris, France). The milled fractions were obtained after the processing of 8 kg of whole grain wheat in a Bühler mill: 22% bran + remilling, 78% white flour (0.55 g/100 g of ash). The whole wheat flour diet (Valoris) was reconstituted with 54.7% white flour and 15.3% bran + remilling. The white flour diet (White Fv) comprised 54.7% white flour. The wheat bran diet (Bv) was made up of 15.3% bran + remilling. Duriac was provided by INRA Montpellier (Institut National de la Recherche Agronomique). The milling process was performed and the milled fractions were blended to produce the whole wheat flour.

Animals and diets.

Wistar rats (IFFA-CREDO, l’Arbresle, France), weighing 150 g, were housed, two per cage, in temperature-controlled rooms (22°C), with a dark period from 800 to 2000 h and access to food from 800 to 1600 h. For the intestinal perfusion experiment, rats were fed a standard semipurified diet [73% wheat starch, 15% casein, 3.5% mineral mixture (AIN 93M formula), 1% vitamin mixture (AIN 76A formula), 5% corn oil] for 2 wk. The rats were maintained and handled according to the recommendations of the Institut National de la Recherche Agronomique Ethics Committee, in accordance with decree no. 87–848.

To study the bioavailability of FA in cereals and in FA-supplemented diets, rats were fed one of the experimental semipurified diets distributed as a moistened powder for 21 d (Table 1 ). The composition of the purified diets was the same as that of the control diet but enriched in ferulic acid at different concentrations, so that rats consumed 10, 50 and 250 µmol/d ferulic acid (FA 10, FA 50 and FA 250 diets, respectively). The body weight of rats was recorded twice per week during the experimental period. During the last 7 d of the experimental period, rats were transferred to metabolic cages and food intake and fecal excretion were recorded over the last 4 d of the experiment.

For the intestinal perfusion, rats were anesthetized with sodium pentobarbital (40 mg/kg body) 18 h after the beginning of the meal and maintained alive during the perfusion period. In all experiments, a cannulation of the biliary duct was performed to test the enterohepatic cycling of ferulic acid. After cannulation of the biliary duct, a perfusion of jejunal + ileal segment of intestine (from 5 cm distal from the flexura duodenojejununalis to the valvula ileocoecalis) was prepared by installing cannulae at each extremity. This segment was continuously perfused in situ with a buffer containing KH₂PO₄ (5 mmol/L), K₂HPO₄ (2.5 mmol/L), NaHCO₃ (5 mmol/L), NaCl (50 mmol/L), KCl (40mmol/L), potassium tricitrate (10 mmol/L), CaCl₂ (2mmol/L), MgCl₂ (2 mmol/L), pH 6.7, glucose (8 mmol/L) and taurocholic acid (1 mmol/L) at a flow rate of 1 mL/min, at 37°C and supplemented with 10, 20 and 50 µmol/L ferulic acid. Aliquots of effluent were collected directly at the exit of the ileum into plastic tubes (1.5 mL) during the last 5 min of perfusion. All volumes were recorded and concentrations were corrected for intestinal absorption of water. Bile was collected throughout the perfusion step. At the end of the experiment, blood samples were withdrawn from the abdominal aorta into heparinized tubes. Plasma, bile and perfusate samples were acidified with 10 mmol/L acetic acid and then stored at -20°C.

To study the bioavailability of ferulic acid in cereals, rats were killed at the end of the dark period, when cecal fermentations are still very active. They were first anesthetized with sodium pentobarbital (40 mg/kg body) and maintained at 37°C. An abdominal incision was made and blood was withdrawn from the abdominal aorta (5 mL) into heparinized tubes. After centrifugation at 10,000 x g for 5 min, the plasma was collected, acidified with acetic acid (10 mmol/L) and stored at -20°C for FA analysis. After blood sampling, the cecum with its contents was removed and weighed and two samples of cecal contents were transferred to microfuge tubes and immediately frozen at -20°C.

Sample treatment.

Bile, plasma, urine and perfusate samples were acidified (to pH 4.9) with 0.1 volume of 0.58 mol/L acetic acid. The samples were treated for 30 min at 37°C in the absence (unconjugated forms) or in the presence (total forms) of 5 x 10⁶ units/L ß-glucuronidase and 2.5 x 10⁵ units/L sulfatase. The reactions were stopped by the addition of 2.85 volumes of methanol/HCl (200 mmol/L) and the resulting mixtures were centrifuged for 4 min at 14,000 x g. After this extraction step, 20 µL of supernatant was injected and analyzed by HPLC.

Cereals and fecal samples (200 mg) were saponified for 2 h in the dark with 10 mL of 2 mol/L NaOH at 35°C (with agitation, in the presence of N₂). 3,4,5 Trimethoxy-trans-cinnamic acid was then added as an internal standard and the solutions were adjusted to pH 2.0 with 4 mol/L HCl. The phenolic acids were extracted once with ethyl acetate (5 mL) under agitation and 5 min centrifugation at 3800 x g. The ether phases were collected in amber test tubes and evaporated completely in the presence of N₂. The dry extracts were dissolved in 2 mL of methanol. A quantity of the supernatant (20 µL) was injected and analyzed by HPLC.

Chromatographic conditions.

The HPLC system used consisted of an autosampler (Kontron, 360), a UV Detector (set at 320 nm) and a Software system for data recording and processing. The system was fitted with a 5-µm C-18 Hypersil BDS analytical column (150 x 4.6 mm; Life Sciences International, Cergy, France). The mobile phase consisted of 50 mmol/L CH₃COONa (pH 4) (solvent A) and acetonitrile (solvent B). The chromatographic conditions were as follows (flow rate 1 mL/min): 0–3 min: solvent A 85%/solvent B 15%; 3–33 min: solvent A 85%/solvent B 15% solvent A 65%/solvent B 35%; 33–34 min: solvent A 40%/solvent B 60%; 34–36 min: solvent A 40%/solvent B 60%; 36–37 min: return to initial mobile phase conditions, then equilibration for 3 min.

The plasma samples obtained during the study of ferulic acid bioavailability in cereals and supplemented diets were analyzed using a multielectrode coulometric detection (4-electrodes CoulArray, Eurosep, France) with potentials set at 150, 270, 370 and 450 mV.

Statistics.

Values are means ± SEM, and the differences between values were determined by the Kruskal-Wallis test (nonparametric ANOVA), and Dunn’s Multiple Comparisons Test was used to separate means.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Intestinal and hepatic metabolism of ferulic acid.

Three different concentrations of FA, ranging from 10 to 50 µmol/L, were perfused through the small intestine in situ, and the absorption of this compound was directly proportional to the amount perfused (Fig. 1 ; Table 2 ). The percentage absorbed, corresponding to the net absorption, did not differ at any of the concentrations (56.1 ± 2.3% of the perfused dose). Moreover, the concentration of ferulic acid recovered in the effluent was not affected by the enzymatic treatment, suggesting that this compound was present only as its native form at the end of the perfusion step.

View larger version (15K): [in this window] [in a new window]   FIGURE 1 Absorption of ferulic acid (FA) in the small intestine of rats after in situ perfusion of three concentrations of this compound for 30 min. Values are means ± SEM, n = 5.

At the end of the perfusion period, in nonhydrolyzed plasma, no trace of unconjugated FA was found, indicating that the circulating forms of this compound were glucurono- and/or sulfoconjugates. However, these FA metabolites were not detected in nonhydrolyzed samples, probably because their response to UV detection was too low under the present chromatographic conditions. The concentration of FA in hydrolyzed plasma depended on the perfused dose and increased as a function of the perfused dose (Table 2) .

A fraction of the ferulic acid perfused dose was not recovered in the effluent and in the bile at the end of the perfusion step. This unrecovered part could correspond to the conjugated ferulic acid distributed in different organs; as a consequence, it could have a potential biological effect. By calculating the difference between these total outputs from the perfused intestine (nonabsorbed FA and biliary secretion) and the perfused dose in the intestine, we estimated the proportion of conjugated forms available for peripheral tissues (Fig. 2 ; Table 2 ). This percentage of conjugated forms available for peripheral tissues represented 45–53% of the perfused dose.

View larger version (51K): [in this window] [in a new window]   FIGURE 2 Recapitulative schematic of the fate of ferulic acid (FA) at the splanchnic level. The diagram shows the FA percentage at the splanchnic level after perfusion of the jejuno-ileal segment by FA. Under these conditions, 56.1% of perfused FA enters the enterocytes by an as yet unidentified mechanism. In these cells, FA is readily conjugated and the resulting metabolites can leave the intestinal cells only toward the serosal side because no conjugated forms of FA are detected in the intestinal lumen. Under such conditions, 56.1% of perfused FA, corresponding to the net absorption, is recovered in the plasma of the mesenteric vein as conjugated derivatives. A part of these conjugates enters into the hepatocytes and is secreted in the bile (6%). Under these conditions, 49.9% of the perfused dose is distributed in the peripheral tissues and may have biological effects.

The level of FA in feces was negligible whatever the dose of FA ingested (Table 3 ). This result suggests that this compound was either highly absorbed by the gastrointestinal tract and/or extensively catabolized by the microflora present in the cecum.

FA urinary excretion was proportional to the ingested dose (R² = 0.995) (Table 3) . This observation supports the view that this compound was quite highly absorbed. Moreover, because the plasma concentrations were relatively low or even undetectable 18 h after the beginning of the meal, it is likely that absorbed FA was readily eliminated in urine.

Bioavailability of FA in cereals.

The presence of whole cereals or cereal fractions in the diet did not affect daily food intake or weight gain (Table 4 ). Rats fed cereal diets had significantly greater fecal excretions than controls (P < 0.001) or rats fed FA enriched diets, except rats fed White Fv. All rats fed cereal diets had enlarged ceca compared with controls. However, only rats fed Bv + resistant starch (RS) had significantly heavier ceca than controls. In the same way, these rats and rats fed White Fv had greater short-chain fatty acid fermentation in the cecum than controls and Bv-fed rats.

In the Valoris cultivar, compared with whole wheat flour, 90% of FA was found in the bran (Table 5 ). In rats fed whole wheat Valoris and bran (Bv diet), the fecal excretion of FA was high and the urinary excretion was low. The percentage of FA recovered in urine, in relation to the ingested dose, was not different between Valoris- and Bv-fed groups (Table 5) . The addition of RS to the Bv diet did not contribute to an increase in the fecal excretion of FA. The ingested FA in rats fed white Fv was significantly lower than in rats fed Valoris or Bv diets, which explains the low fecal and urinary excretion in rats fed White Fv (Table 5) . However, the urinary excretion in relation to the ingested dose was significantly higher (Table 5) .

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

Some biological effects have been described in the literature. It has been shown that FA has strong anti-inflammatory properties (20 ), inhibits chemically induced carcinogenesis in rats and inhibits tumor promotion in mouse skin (21 ,22 ). Oxidation of LDL is important in the pathogenesis of atherosclerosis, and recent studies have reported that FA plays a role as an antioxidant, inhibiting lipid peroxidation (23 ) and LDL oxidation (17 ), and scavenging oxygen radicals (14 ). Thus, FA could be useful in the prevention of cardiovascular diseases and cancers. Nevertheless, its biological properties depend on its bioavailability, notably in a complex matrix such as cereals. Because such foods certainly influence polyphenol bioavailability, it is necessary to assess its actual bioavailability in experimental diets supplemented with FA.

An in situ model of intestinal perfusion was used to determine whether the intestinal or hepatic metabolism of FA were limiting steps for its bioavailability. The effect of FA dose on absorption was investigated by perfusion at three different concentrations. FA absorption was directly proportional to the perfused concentration. This suggests that FA could be absorbed by passive diffusion or by a facilitated transport which appears not to be saturated even at a luminal concentration of 50 µmol/L. A comparative study showed that cinnamate uptake is a linear function of substrate concentrations between 25 and 500 µmol/L (24 ). This result is consistent with our findings that FA absorption is directly proportional to the perfused concentration (10–50 µmol/L). However, at higher cinnamate concentrations (0.5–5 mmol/L), absorption of this compound could be described by a Michaëlis-Menten type equation with a saturable transport component, and in particular, by a Na⁺/dependent carrier-mediated transport process (24 ). These authors observed a competition between cinnamate and FA for absorption and concluded that compounds structurally related to FA are absorbed across the brush border membrane of rat jejunum by the same transporter. The absorption of FA seems to depend on a Na⁺/dependent carrier-mediated transport process that was not saturated at 50 µmol/L; however, further experiments are required to firmly identify the transporter involved (24 ).

In the perfused isolated intestine, Spencer et al. (25 ) showed that FA was present on the serosal side as glucuronidated FA, suggesting that this compound could be metabolized by intestinal conjugation enzymes. This conjugation process seems to be common to most polyphenols (26 –29 ), and flavonoids in particular. Using the same intestinal model, 67% of quercetin aglycone was shown to be absorbed and conjugated by the intestine, and 15% of quercetin conjugates secreted toward the serosal side (28 ). Under these conditions, the majority of absorbed quercetin was then reexcreted as conjugates into the intestinal lumen (28 ). Intestinal secretion of conjugated metabolites may constitute an important step for control of polyphenol availability, but our results suggest that this efflux of FA conjugated forms does not occur. Under these conditions, all of the absorbed FA was secreted toward the serosal side (Fig. 2) . This could be due to the nature of the conjugates synthesized in the enterocytes, which could influence the channeling of the conjugates, i.e., secreted toward either the serosal side or the mucosal side.

In bile and in aorta plasma, only FA could be detected after enzymatic hydrolysis, suggesting that this compound was present only as the conjugated form. Nevertheless, it is conceivable that FA was also present as the unconjugated form in these biological fluids, but at concentrations below the limit of detection (0.5 µmol/L).

Whatever the flux of absorbed FA, 6% of the perfused dose was recovered in bile (Fig. 2) . This suggests that the biliary secretion was proportional to the perfused dose and not saturated. Under these conditions, the fraction available for the tissues was 50%, whatever the dose absorbed (Fig. 2) . This value is quite substantial because, for example, only 9% of perfused quercetin was found available for these tissues (28 ). The fractional availability of FA is relatively important, suggesting that the intestinal and hepatic metabolism of this compound is not a limiting step for its bioavailability.

The bioavailability of FA was studied in rats fed a diet supplemented with FA for 3 wk to achieve a daily intake of 10, 50 or 320 µmol FA/d. The control diet contained 0.003% FA, present in the purified wheat starch (Table 3) . In plasma, FA was present only as conjugated forms. This result is in accordance with Azuma et al. (30 ), showing that phenolic acids, such as caffeic and chlorogenic acids are present in plasma as glucuronided and/or sulfated forms, with only a minor part of these compounds identified as the unconjugated form. We did not detect unconjugated FA, possibly because they were present in concentrations below of the detection limit. However, Azuma et al. (30 ) used a procedure (gavage) delivering a large amount of compound in a short time, leading to a direct diffusion of the compound administered through the intestinal wall; this could explain the presence of unconjugated caffeic acid in plasma.

In the present work (postabsorptive conditions), the plasma concentrations of FA were very low in rats fed FA diets. Azuma et al. (30 ) showed that the T_max of caffeic acid was 2 h and rapidly returned to undetectable values within 6 h after gavage. This observation suggests that the enterohepatic cycle did not allow the plasma concentrations of this compound to remain high. This agrees with the result obtained by in situ intestinal perfusion of FA because only 6.2 ± 0.9% of the perfused dose was secreted into the bile (Fig. 2) .

The urinary excretion of FA was between 38 and 51% of the ingested dose. When rats were fed 15 µmol FA/d, the plasma concentration of this compound was not detectable 18 h after the beginning of the meal, suggesting that absorbed FA was completely eliminated in urine. These results are consistent with those found in in situ intestinal perfusion because 50% of the perfused dose was available for peripheral tissues and thus for urinary excretion. This substantial recovery is noteworthy compared with that found by Choudhury et al. (18 ), showing that only 10.5% of FA ingested was present in urine 24 h after the beginning of the meal. Despite the substantial urinary recovery of FA, a part of the ingested dose of this compound was not recovered because a weak fraction was detected in the feces. This unrecovered fraction could be due to the degradation of FA by the microflora. Decarboxylation of phenolic acids occurs readily when they ware incubated anaerobically with extracts of cecum or colon contents or feces (31 ).

When FA was ingested in whole cereal (1.2 mg/g) or bran (4.6 mg/g), the recovery of ferulic acid in urine was quite limited. This suggests that its absorption is much lower than when FA is present in the diet as a free acid. In fact, the presence of ester-linked monomeric and dimeric phenolics leads to reduced biodegradability of the cell wall polysaccharide, and limits the release of ferulic acid. Diferulates have a dramatic effect on both the rate and extent of polysaccharide degradation. Cross-linking through diferulates may inhibit the binding of endoxylanases, thus limiting the extent of arabinoxylan degradation and consequently the release of esterified ferulic acid (32 ). Furthermore, cross-linking may prevent localized areas from swelling, excluding key enzymes for dietary fiber degradation (33 ). The form of the acid and its location in the plant affect its fate after ingestion by mammals. Covalently bound phenolic acids are released only after extensive microbial attack and thus at sites of maximum microbial activity in the colon (34 ). Degradative enzymes with molecular weights > 20 kDa would be totally excluded from most of the pores in the wheat samples and even a 20- to 30-kDa enzyme would have difficulty diffusing across the small numbers of pores with radii of 2.5–4 nm (35 ). As a result, these enzymes with a Stokes radius of >20 kDa are unable to diffuse into the hydrated wall surface. All of these observations may explain why FA present in whole wheat or bran is highly recovered in feces and poorly recovered in urine.

The percentage of FA recovered in urine in relation to the ingested dose was significantly higher in rats fed white Fv than in rats fed Bv. The bran fraction presents a well-defined pore structure compared with the endosperm fraction. The latter, which is made up chiefly of starch, presents a much more diffuse pattern and little evidence of structure, thus yielding a more easily degradable substance (35 ). Moreover, approximately one third of unlignified endosperm arabinoxylans are soluble in water in contrast to the acid arabinoxylan from pericarp, which is mainly insoluble. This explains why nonstarch polysaccharides in primary cell walls from endosperm are more extensively broken down than fiber in secondary lignified cell walls from the pericarp (cf. Table 4 ). Therefore, FA linked to arabinoxylan in the endosperm is more easily released after enzymatic and microbial degradation.

The rate of release of esterified FA from a complex matrix in the digestive tract appears dependent on the nature of the fibers to which it is linked, but also on its concentration in the matrix. Therefore, the greater the concentration of ferulic acid in the matrix, the more probable the dimer formation, which implies a modification of the physical and chemical properties of the fiber. However, when administered in meals as a free acid, FA is easily absorbed and its intestinal and hepatic metabolism do not limit its bioavailability.

In plasma, FA was present only as conjugated forms; under these conditions, the biological effects of its metabolites require investigation. In humans, little is known about the biological protective effects of FA metabolites. It has been shown that FA in the glucuronidated form conserves its ability to protect LDL oxidation in an in vitro system (17 ). These protective effects could occur only during the postprandial period because FA conjugates were rapidly eliminated in urine after a meal. Human studies should be pursued to evaluate the bioavailability of FA and its biological effects after ingestion of a cereal matrix, which is a common food.

	FOOTNOTES

 
¹ Supported by A.N.R.T. (Association Nationale pour la Recherche et Technique), I.N.R.A. (Institut National de la Recherche Agronomique), Univers Céréales and I.T.C.F. (Institut Technique des Céréales et des Fourrages).

³ Abbreviations used: Bv, bran Valoris diet; FA, ferulic acid; RS, resistant starch; Valoris, whole wheat flour diet; White Fv, white flour Valoris diet.

Manuscript received 11 February 2002. Initial review completed 10 March 2002. Revision accepted 8 April 2002.

	LITERATURE CITED

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 

1. Jacobs, D. R., Jr., Marquart, L., Slavin, J. & Kushi, L. H. (1998) Whole-grain intake and cancer: an expanded review and meta-analysis. Nutr. Cancer 30:85-96.[Medline]

2. Jacobs, D. R., Pereira, M. A., Meyer, K. A. & Kushi, L. H. (2000) Fiber from whole grains, but not refined grains, is inversely associated with all-cause mortality in older women: the Iowa women’s health study. J. Am. Coll. Nutr. 19:326S-330S.[Abstract/Free Full Text]

3. Meyer, K. A., Kushi, L. H., Jacobs, D. R., Jr., Slavin, J., Sellers, T. A. & Folsom, A. R. (2000) Carbohydrates, dietary fiber, and incident type 2 diabetes in older women. Am. J. Clin. Nutr. 71:921-930.[Abstract/Free Full Text]

4. Pietinen, P., Rimm, E. B., Korhonen, P., Hartman, A. M., Willett, W. C., Albanes, D. & Virtamo, J. (1996) Intake of dietary fiber and risk of coronary heart disease in a cohort of Finnish men. The Alpha-Tocopherol Beta-Carotene Cancer Prevention Study. Circulation 94:2720-2727.[Abstract/Free Full Text]

5. Fraser, G. E., Sabate, J., Beeson, W. L. & Strahan, T. M. (1992) A possible protective effect of nut consumption on risk of coronary heart disease. The Adventist Health Study. Arch. Intern. Med. 152:1416-1424.[Abstract]

6. Liu, S., Stampfer, M. J., Hu, F. B., Giovannucci, E., Rimm, E., Manson, J. E., Hennekens, C. H. & Willett, W. C. (1999) Whole-grain consumption and risk of coronary heart disease: results from the Nurses’ Health Study. Am. J. Clin. Nutr. 70:412-419.[Abstract/Free Full Text]

7. Anderson, J. W., Hanna, T. J., Peng, X. & Kryscio, R. J. (2000) Whole grain foods and heart disease risk. J. Am. Coll. Nutr. 19:291S-299S.[Abstract/Free Full Text]

8. Wolk, A., Manson, J. E., Stampfer, M. J., Colditz, G. A., Hu, F. B., Speizer, F. E., Hennekens, C. H. & Willett, W. C. (1999) Long-term intake of dietary fiber and decreased risk of coronary heart disease among women. J. Am. Med. Assoc. 281:1998-2004.[Abstract/Free Full Text]

9. Slavin, J. L., Jacobs, D., Marquart, L. & Wiemer, K. (2001) The role of whole grains in disease prevention. J. Am. Diet. Assoc. 101:780-785.[Medline]

10. Smith, M. M. & Hartley, R. D. (1983) Occurrence and nature of ferulic acid substitution of cell wall polysaccharides in gramineous plants. Carbohydr. Res. 118:65-80.

11. Fulcher, R. G. (1983) Fluorescence microscopy of cereals. New Frontiers in Food Microstructure 1983:167-175 American Association of Cereal Chemists Ottawa, Canada. .

12. Sosulski, F., Krygier, K. & Hogge, L. (1982) Free esterified and extractable-bond phenolics acids. III. Composition of phenolic acids in cereal and potato flours. J. Agric. Food Chem. 30:337-340.

13. Lempereur, I., Rouau, X. & Abecassis, J. (1997) Genetic and agronomic variation in arabinoxylan and ferulic acid contents of durum wheat (Triticum durum L.) grain and its milling fractions. J. Cereal Sci. 25:103-110.

14. Graf, E. (1992) Antioxidant potential of ferulic acid. Free Radic. Biol. Med. 13:435-448.[Medline]

15. Castelluccio, C., Bolwell, G. P., Gerrish, C. & Rice-Evans, C. (1996) Differential distribution of ferulic acid to the major plasma constituents in relation to its potential as an antioxidant. Biochem. J. 316:691-694.

16. Garcia-Conesa, M. T., Plumb, G. W., Kroon, P. A. & Wallace, G. (1997) Antioxidant properties of ferulic acid dimers. Redox Rep 3:239-244.

17. Ohta, T., Nakano, T., Egashira, Y. & Sanada, H. (1997) Antioxidant activity of ferulic acid beta-glucuronide in the LDL oxidation system. Biosci. Biotechnol. Biochem. 61:1942-1943.[Medline]

18. Choudhury, R., Srai, S. K., Debnam, E. & Rice-Evans, C. A. (1999) Urinary excretion of hydroxycinnamates and flavonoids after oral and intravenous administration. Free Radic. Biol. Med. 27:278-286.[Medline]

19. Bourne, L. C. & Rice-Evans, C. (1998) Bioavailability of ferulic acid. Biochem. Biophys. Res. Commun. 253:222-227.[Medline]

20. Chawla, A. S., Singh, M., Murthy, M. S., Gupta, M. P. & Singh, H. (1987) Anti-inflammatory action of ferulic acid and its esters in carrageenan-induced rat paw edema model. Indian J. Exp. Biol. 25:187-189.[Medline]

21. Imaida, K., Hirose, M., Yamaguchi, S., Takahashi, S. & Ito, N. (1990) Effects of naturally occurring antioxidants on combined 1,2-dimethylhydrazine- and 1-methyl-1-nitrosourea-initiated carcinogenesis in F344 male rats. Cancer Lett 55:53-59.[Medline]

22. Huang, M. T., Smart, R. C., Wong, C. Q. & Conney, A. H. (1988) Inhibitory effect of curcumin, chlorogenic acid, caffeic acid, and ferulic acid on tumor promotion in mouse skin by 12-O-tetradecanoylphorbol-13-acetate. Cancer Res 48:5941-5946.[Abstract/Free Full Text]

23. Uchida, M., Nakajin, S., Toyoshima, S. & Shinoda, M. (1996) Antioxidative effect of sesamol and related compounds on lipid peroxidation. Biol. Pharm. Bull. 19:623-626.[Medline]

24. Wolffram, S., Weber, T., Grenacher, B. & Scharrer, E. (1995) A Na(+)-dependent mechanism is involved in mucosal uptake of cinnamic acid across the jejunal brush border in rats. J. Nutr. 125:1300-1308.

25. Spencer, J. P., Chowrimootoo, G., Choudhury, R., Debnam, E. S., Srai, S. K. & Rice-Evans, C. (1999) The small intestine can both absorb and glucuronidate luminal flavonoids. FEBS Lett 458:224-230.[Medline]

26. Walle, U. K., Galijatovic, A. & Walle, T. (1999) Transport of the flavonoid chrysin and its conjugated metabolites by the human intestinal cell line Caco-2. Biochem. Pharmacol. 58:431-438.[Medline]

27. Donovan, J. L., Crespy, V., Manach, C., Morand, C., Besson, C., Scalbert, A. & Rémésy, C. (2001) Catechin is metabolized by both the small intestine and liver of rats. J. Nutr. 131:1753-1757.[Abstract/Free Full Text]

28. Crespy, V., Morand, C., Manach, C., Besson, C., Demigné, C. & Rémésy, C. (1999) Part of quercetin absorbed in the small intestine is conjugated and further secreted in the intestinal lumen. Am. J. Physiol. 277:G120-G126.[Abstract/Free Full Text]

29. Andlauer, W., Kolb, J., Stehle, P. & Furst, P. (2000) Absorption and metabolism of genistein in isolated rat small intestine. J. Nutr. 130:843-846.[Abstract/Free Full Text]

30. Azuma, K., Ippoushi, K., Nakayama, M., Ito, H., Higashio, H. & Terao, J. (2000) Absorption of chlorogenic acid and caffeic acid in rats after oral administration. J. Agric. Food Chem. 48:5496-5500.[Medline]

31. Scheline, R. R. (1966) The decarboxylation of some phenolic acids by the rat. Acta Pharmacol. Toxicol. (Copenh). 24:275-285.[Medline]

32. Grabber, J. H., Hatfield, R. D. & Ralph, J. (1998) Diferulate cross-links impede the enzymatic degradation of non-lignified maize walls. J. Sci. Food Agric. 77:193-200.

33. Bunzel, M., Ralph, J., Marita, J., Hatfield, R. & Steinhart, H. (2001) Diferulates as structural components in soluble and insoluble cereal dietary fibre. J. Sci. Food Agric. 81:653-660.

34. Chesson, A., Provan, G., Russell, W., Scobbie, L., Richardson, A. & Stewart, C. (1999) Hydroxycinnamic acids in the digestive tract of livestock and humans. J. Sci. Food Agric. 79:373-378.

35. Chesson, A., Gardner, P. & Wood, T. (1997) Cell wall porosity and available surface area of wheat straw and wheat grain fractions. J. Sci. Food Agric. 75:289-295.

This article has been cited by other articles:

				A. Fardet, R. Llorach, A. Orsoni, J.-F. Martin, E. Pujos-Guillot, C. Lapierre, and A. Scalbert Metabolomics Provide New Insight on the Metabolism of Dietary Phytochemicals in Rats J. Nutr., July 1, 2008; 138(7): 1282 - 1287. [Abstract] [Full Text] [PDF]

				L. Poquet, M. N. Clifford, and G. Williamson Transport and Metabolism of Ferulic Acid through the Colonic Epithelium Drug Metab. Dispos., January 1, 2008; 36(1): 190 - 197. [Abstract] [Full Text] [PDF]

				A. Fardet, C. Canlet, G. Gottardi, B. Lyan, R. Llorach, C. Remesy, A. Mazur, A. Paris, and A. Scalbert Whole-Grain and Refined Wheat Flours Show Distinct Metabolic Profiles in Rats as Assessed by a 1H NMR-Based Metabonomic Approach J. Nutr., April 1, 2007; 137(4): 923 - 929. [Abstract] [Full Text] [PDF]

				C. Manach, G. Williamson, C. Morand, A. Scalbert, and C. Remesy Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies Am. J. Clinical Nutrition, January 1, 2005; 81(1): 230S - 242S. [Abstract] [Full Text] [PDF]

				Z. Zhao, Y. Egashira, and H. Sanada Ferulic Acid Is Quickly Absorbed from Rat Stomach as the Free Form and Then Conjugated Mainly in Liver J. Nutr., November 1, 2004; 134(11): 3083 - 3088. [Abstract] [Full Text] [PDF]

				C. Manach, A. Scalbert, C. Morand, C. Remesy, and L. Jimenez Polyphenols: food sources and bioavailability Am. J. Clinical Nutrition, May 1, 2004; 79(5): 727 - 747. [Abstract] [Full Text] [PDF]

				M.-P. Gonthier, M.-A. Verny, C. Besson, C. Remesy, and A. Scalbert Chlorogenic Acid Bioavailability Largely Depends on Its Metabolism by the Gut Microflora in Rats J. Nutr., June 1, 2003; 133(6): 1853 - 1859. [Abstract] [Full Text] [PDF]

				Z. Zhao, Y. Egashira, and H. Sanada Ferulic Acid Sugar Esters Are Recovered in Rat Plasma and Urine Mainly as the Sulfoglucuronide of Ferulic Acid J. Nutr., May 1, 2003; 133(5): 1355 - 1361. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Adam, A. Articles by Rémésy, C. Search for Related Content PubMed PubMed Citation Articles by Adam, A. Articles by Rémésy, C.