Alkylresorcinols in cereals and cereal products

Effects of alkylresorcinols on volume and structure of yeast-leavened bread

BACKGROUND

Alkylresorcinols (AR) are amphiphilic phenolic compounds found in high amounts in wheat, durum wheat and rye, with different homologue composition for each cereal. The effect of different amounts of added AR from these cereals on bread volume, height, porosity and microstructure was studied. Breads with added rye bran (with high levels of AR) or acetone-extracted rye bran (with low levels of AR) were also baked, as well as breads with finely milled forms of each of these brans.

RESULTS

Breads with high amounts of added AR, irrespective of AR homologue composition, had a lower volume, a more compact structure and an adverse microstructure compared with breads with no or low levels of added AR. AR were also shown to inhibit the activity of baker's yeast. There was no difference in bread volume and porosity between bread baked with rye bran and acetone-extracted rye bran or with brans of different particle size.

CONCLUSION

Irrespective of homologue composition, AR had a negative effect on wheat bread properties when added in high amounts as purified extracts from wheat, durum wheat and rye. Natural levels of AR in rye bran, however, did not affect the volume and porosity of yeast-leavened wheat breads.

Plasma and urinary alkylresorcinol metabolites as potential biomarkers of breast cancer risk in Finnish women: a pilot study

Alkylresorcinols (ARs) are shown to be good biomarkers of consumption of rye and whole-grain wheat products in man. The aim of this pilot study was to investigate AR metabolites as potential biomarkers of breast cancer (BC) risk in Finnish women since intake of cereal fiber and its components has been proposed to reduce this risk through an effect on the enterohepatic circulation of estrogens. This was a cross-sectional and observational pilot study. A total of 20 omnivores, 20 vegetarians, and 16 BC women (6-12 mo after operation) were investigated on 2 occasions 6 mo apart. Dietary intake (5-days record), plasma/urinary AR metabolites [3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA)] and plasma/urinary enterolactone were measured. The groups were compared using nonparametric tests. We observed that plasma DHBA (P = 0.007; P = 0.03), plasma DHPPA (P = 0.02; P = 0.01), urinary DHBA (P = 0.001; P = 0.003), urinary DHPPA (P = 0.001; P = 0.001), and cereal fiber intake (P = 0.007; P = 0.003) were significantly lower in the BC group compared to the vegetarian and omnivore groups, respectively. Based on measurements of AR metabolites in urine and in plasma, whole-grain rye and wheat cereal fiber intake is low in BC subjects. Thus, urinary and plasma AR metabolites may be used as potential biomarkers of BC risk in women. This novel approach will likely also facilitate studies of associations between rye and whole-grain wheat cereal fiber intake and other diseases. Our findings should, however, be confirmed with larger subject populations.

Can rye intake decrease risk of human breast cancer?

BACKGROUND

Rye contains more fibre and bioactive compounds than other cereals used for bread production. The fibre and compounds of the fibre complex could provide protection against breast cancer (BC).

OBJECTIVE

To review the evidence and theoretical background for a role of rye and some of its components in the prevention of BC.

DESIGN

A short review based to a great extent on the work by scientists in the Nordic countries.

RESULTS

Some of the possible mechanisms by which the fibre complex could reduce BC risk are presented. The fibre through its effect on fermentation increases esterification of bile acids reducing toxicity of the free bile acids and is involved in the production of butyrate with potential anticancer effects including BC. The fibre reduces the enterohepatic circulation of the oestrogens leading to lower plasma oestrogen concentrations. The fibre complex contains bioactive compounds such as lignans and alkylresorcinols that are antioxidative and potentially anticarcinogenic. In addition, vitamins, minerals, and phytic acid in rye may provide protection against BC.

CONCLUSION

Rye products made from wholegrain rye flour are likely to contribute to reduced BC risk.

Alkylresorcinol biosynthesis in plants: new insights from an ancient enzyme family?

Alkylresorcinols are members of an extensive family of bioactive compounds referred to as phenolic lipids, which occur primarily in plants, fungi, and bacteria. In plants, alkylresorcinols and their derivatives are thought to serve important roles as phytoanticipins and allelochemicals, although direct evidence for this is still somewhat lacking. Specialized type III polyketide synthases (referred to as 'alkylresorcinol synthases'), which catalyze the formation of 5-alkylresorcinols using fatty acyl-CoA starter units and malonyl-CoA extender units, have been characterized from several microbial species, however until very recently little has been known concerning their plant counterparts. Through the use of sorghum and rice EST and genomic data sets, significant inroads have now been made in this regard. Here we provide additional information concerning our recent report on the identification and characterization of alkylresorcinol synthases from Sorghum bicolor and Oryza sativa, as well as a brief consideration of the emergence of this intriguing subfamily of enzymes.

Effects of environment and variety on alkylresorcinols in wheat in the HEALTHGRAIN diversity screen

Alkylresorcinols (AR), phenolic lipids found in high amounts in whole grain wheat and rye, can be used as biomarkers for these cereals. The content (on a dry matter basis) and homologue composition of AR were determined in 26 wheat varieties grown in Hungary in 2005-2007, as well as in the United Kingdom, France, and Poland in 2007. There was a significant effect of year, location, and variety on both total AR and individual AR homologue content (p<0.001). A warm and dry climate generally resulted in higher AR contents, whereas high precipitation especially during plant development and grain-filling resulted in lower contents. There was a significant negative correlation between AR content and thousand-kernel weight (p<0.001), which may be explained by the warm and dry climate giving smaller kernels with higher AR content. The difference between varieties was generally consistent, with highest and lowest AR contents for the same varieties during different years and at different locations (p<0.001). Total AR content was correlated with the relative proportions of the different homologues, with a relatively lower concentration of homologues C17:0 and C19:0 and a lower C17:0/C12:0 ratio at higher overall contents. The results show that AR content is a highly heritable phytochemical component but that it is also affected by the environment.

New hypotheses for the health-protective mechanisms of whole-grain cereals: what is beyond fibre?

Epidemiological studies have clearly shown that whole-grain cereals can protect against obesity, diabetes, CVD and cancers. The specific effects of food structure (increased satiety, reduced transit time and glycaemic response), fibre (improved faecal bulking and satiety, viscosity and SCFA production, and/or reduced glycaemic response) and Mg (better glycaemic homeostasis through increased insulin secretion), together with the antioxidant and anti-carcinogenic properties of numerous bioactive compounds, especially those in the bran and germ (minerals, trace elements, vitamins, carotenoids, polyphenols and alkylresorcinols), are today well-recognised mechanisms in this protection. Recent findings, the exhaustive listing of bioactive compounds found in whole-grain wheat, their content in whole-grain, bran and germ fractions and their estimated bioavailability, have led to new hypotheses. The involvement of polyphenols in cell signalling and gene regulation, and of sulfur compounds, lignin and phytic acid should be considered in antioxidant protection. Whole-grain wheat is also a rich source of methyl donors and lipotropes (methionine, betaine, choline, inositol and folates) that may be involved in cardiovascular and/or hepatic protection, lipid metabolism and DNA methylation. Potential protective effects of bound phenolic acids within the colon, of the B-complex vitamins on the nervous system and mental health, of oligosaccharides as prebiotics, of compounds associated with skeleton health, and of other compounds such as alpha-linolenic acid, policosanol, melatonin, phytosterols and para-aminobenzoic acid also deserve to be studied in more depth. Finally, benefits of nutrigenomics to study complex physiological effects of the 'whole-grain package', and the most promising ways for improving the nutritional quality of cereal products are discussed.

Health benefits of whole grain phytochemicals

A whole grain consists of the intact, ground, cracked, or flaked caryopsis, whose principal anatomical components--the starchy endosperm, germ, and bran--are present in the same relative proportions as they exist in the intact caryopsis. Whole grain food products can be intact, consisting of the original composition of bran, germ, and endosperm, throughout the entire lifetime of the product, or reconstituted, in which one or more of the original components of a whole grain is recombined to the relative proportion naturally occurring in the grain kernel. Increased consumption of whole grains has been associated with reduced risk of major chronic diseases including cardiovascular disease, type II diabetes, and some cancers. Whole grain foods offer a wide range of phytochemicals with health benefits that are only recently becoming recognized. The unique phytochemicals in whole grains are proposed to be responsible for the health benefits of whole grain consumption. In this paper, whole grain phytochemicals and the health benefits associated with their consumption are reviewed.

Quantification of alkylresorcinols in human plasma by liquid chromatography/tandem mass spectrometry

Alkylresorcinols (AR) are of interest as biomarkers of wholegrain wheat and rye intake in epidemiological studies and are currently mainly measured by gas chromatography/mass spectrometry (GC/MS) after labour-intensive sample preparation including liquid-liquid extraction, solid-phase extraction (SPE) and chemical derivatization. This manuscript describes and validates an alternative approach based on normal-phase liquid chromatography/tandem mass spectrometry for the quantification of alkylresorcinols in human plasma. The method requires neither SPE nor chemical derivatization and has a shortened run time compared to GC/MS. Normal- and reversed-phase columns and various mobile phases were evaluated with and without previous SPE of the samples. Normal-phase chromatography allowed separation of AR from the interfering triacylglycerols, diacylglycerols and sterols and enabled detection of AR even without SPE of the samples. The described method has instrumental lower limits of detection in the 25-75 pg range, and lower limits of quantification in the 75-250 pg range. Pooled human plasma and (2)H(4)-nonadecylresorcinol (internal standard) was applied to calibrate the method in the 20-12 000 nM range. The overall method showed intra-batch precision of 8.6% and an averaged accuracy of 100.2%. Applications for diverse human plasma samples are presented and are compared with the results determined by GC/MS. Based on the presented data; this method requiring less sample preparation is suggested for further evaluation as an alternative to GC/MS for analysis of biomarkers of wholegrain wheat and rye intake in epidemiological studies.

Plasma pharmacokinetics of alkylresorcinol metabolites: new candidate biomarkers for whole-grain rye and wheat intake

BACKGROUND

Alkylresorcinols are phenolic compounds that are present almost exclusively in rye and wheat fiber. Alkylresorcinols are absorbed and thereafter metabolized to 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA), which have been detected in human urine and plasma.

OBJECTIVE

The objective was to determine the plasma pharmacokinetics of DHBA and DHPPA in human subjects to estimate whether they show potential as biomarkers for whole-grain rye and/or wheat intake.

DESIGN

Fifteen human volunteers followed a low-alkylresorcinol diet for 2 d before ingesting a single dose of high-fiber rye bread containing 100 mg alkylresorcinols [corrected]. Plasma samples were collected for 25 h, and the alkylresorcinol metabolites were quantified by HPLC with coulometric electrode array detection.

RESULTS

Maximum concentrations were reached at approximately 6 h for both metabolites, although interindividual variation was found. The half-life was significantly (P < 0.0002) longer for DHPPA (16.3 h) than for DHBA (10.1 h). No significant differences were discovered between women and men in the half-life of each metabolite, which, from a pharmacokinetic point of view, is the most important parameter. The area under the curve differed significantly between DHBA and DHPPA (P < 0.0001) and between women and men (P = 0.03 for DHBA and P = 0.01 for DHPPA). However, when corrected for body weight, the difference between sexes was no longer significant.

CONCLUSIONS

Our results suggest that DHBA and DHPPA are both good candidate biomarkers for whole-grain rye and/or wheat intake; however, DHPPA is the better indicator because of its longer half-life. This could provide a practical tool when investigating the association between diet and diseases.

Applying the FDA definition of whole grains to the evidence for cardiovascular disease health claims

The U.S. FDA defines whole grains as consisting of the intact, ground, cracked, or flaked fruit of the grains whose principal components, the starchy endosperm, germ, and bran, are present in the same relative proportions as they exist in the intact grain. We evaluated the effect of applying the FDA definition of whole grains to the strength of scientific evidence in support of claims for risk reduction of cardiovascular disease (CVD). We concluded that using the FDA definition for whole grains as a selection criterion is limiting, because the majority of existing studies often use a broader meaning to define whole grains. When considering only whole grain studies that met the FDA definition, we found insufficient scientific evidence to support a claim that whole grain intake reduces the risk of CVD. However, a whole grain and reduced risk of CVD health claim is supported when using a broader concept of whole grain to include studies that considered intake of fiber-rich bran and germ as well as whole grain. This type of analysis is complicated by diversity in nutrients and bioactive components among different types of whole grains.

Plasma alkylresorcinol metabolites as potential biomarkers of whole-grain wheat and rye cereal fibre intakes in women

It has been demonstrated that intact plasma alkylresorcinols (AR) and urinary AR metabolites could be used as biomarkers of whole-grain intake. Thereafter, we developed the method for the plasma AR metabolites, which is more convenient and requires less sample pretreatment than the analysis of intact plasma AR. The aim of the present study is to evaluate whether AR metabolites measured in plasma, in the same population, could also be considered as useful biomarkers of cereal fibre. Fifty-six women were recruited in a cross-sectional and observational study. Dietary intake (5-d record) and plasma AR metabolites (3,5-dihydroxybenzoic acid, DHBA; 3-(3,5-dihydroxyphenyl)-1-propanoic acid, DHPPA) were measured. The relationship between plasma AR metabolites and cereal fibre intake was examined using partial correlation and stepwise regression. Cereal fibre intake correlated significantly with plasma DHBA (r 0·411; P = 0·002) and DHPPA (r 0·463; P = 0·000) even after adjustment for BMI and age. Thus, plasma AR metabolites correlate with cereal fibre intake as noted with plasma intact AR and urinary AR metabolites. We observed that plasma DHPPA was the independent predictor of cereal fibre intake, explaining 18 % of the variance (adjusted r2 0·176; P = 0·002). In epidemiological screening, it might be easier to obtain and to collect plasma than urine samples. In addition, the plasma AR metabolites half-life seems longer than those of intact plasma AR, and their measurements are more convenient, and faster. Thus, sum of plasma AR metabolites and more specifically plasma DHPPA seems to be good and specific biomarkers of cereal fibre intake.

Rapid and sensitive analysis of alkylresorcinols from cereal grains and products using HPLC-Coularray-based electrochemical detection

Alkylresorcinols (AR) present in the bran fraction of wheat, rye, and barley grains are of current interest as biomarkers of wholegrain cereal intake. This paper reports the development of a rapid quantitative HPLC method allowing sensitive analysis of AR in cereals in 14 min using coularray (CA) detection. The LOD was 1 ng injected and the LOQ 2.5 ng injected, whereas the intrarun and inter-run CVs were 0.8 and 6.4%, respectively. Analytical recovery determined by spiking ranged from 98 to 107% for AR homologues C15:0-C25:0. The method was used to analyze 79 flour and cereal products, with results in the same range as previous studies using GC analysis. Analysis of wholegrain white wheat were in the same range as other wheat varieties (420-556 microg/g). Use of the CA detector allowed detection of low concentrations of AR in white wheat flour (13-51 microg/g) that had not been reliably detected using previous methods. This method allows rapid throughput analysis of cereal samples, required for validation studies on the use of AR as biomarkers of wholegrain cereal intake.

Reproducibility of plasma alkylresorcinols during a 6-week rye intervention study in men with prostate cancer

Alkylresorcinols (AR), phenolic lipids exclusively present in the outer parts of wheat and rye grains, have been proposed as concentration biomarkers of whole-grain wheat and rye intake. A key feature of a good biomarker is high reproducibility, which indicates how accurately a single sample reflects the true mean biomarker concentration caused by a certain intake. In this study, the short- to medium-term reproducibility of plasma AR was determined using samples from a crossover intervention study, where men with prostate cancer (n = 17) were fed rye whole-grain/bran or refined wheat products for 6-wk periods. AR homologs C17:0 and C21:0 differed between the treatments (P < 0.001). The reproducibility determined by the intraclass correlation coefficient (ICC) was high (intervention period 1: ICC = 0.90 [95% CI = 0.82-0.98], intervention period 2: ICC = 0.88 [95% CI = 0.78-0.98]). The results show that a single fasting plasma sample could be used to estimate the mean plasma AR concentration during a 6-wk intervention period with constant intake at a precision of +/- 20% (80% CI). This suggests that the plasma AR concentration can be used as a reliable short- to medium-term biomarker for whole-grain wheat and rye under intervention conditions where intake is kept constant.

Physical, microscopic and chemical characterisation of industrial rye and wheat brans from the Nordic countries

BACKGROUND

Epidemiological studies show inverse relationship between intake of wholegrain cereals and several chronic diseases. Components and mechanisms behind possible protective effects of wholegrain cereals are poorly understood.

OBJECTIVE

To characterise commercial rye bran preparations, compared to wheat bran, regarding structure and content of nutrients as well as a number of presumably bioactive compounds.

DESIGN

Six different rye brans from Sweden, Denmark and Finland were analysed and compared with two wheat brans regarding colour, particle size distribution, microscopic structures and chemical composition including proximal components, vitamins, minerals and bioactive compounds.

RESULTS

Rye brans were generally greener in colour and smaller in particle size than wheat brans. The rye brans varied considerably in their starch content (13.2-;28.3%), which reflected variable inclusion of the starchy endosperm. Although rye and wheat brans contained comparable levels of total dietary fibre, they differed in the relative proportions of fibre components (i.e. arabinoxylan, beta-glucan, cellulose, fructan and Klason lignin). Generally, rye brans contained less cellulose and more beta-glucan and fructan than wheat brans. Within small variations, the rye and wheat brans were comparable regarding the contents of tocopherols/tocotrienols, total folate, sterols/stanols, phenolic acids and lignans. Rye bran had less glycine betaine and more alkylresorcinols than wheat brans.

CONCLUSIONS

The observed variation in the chemical composition of industrially produced rye brans calls for the need of standardisation of this commodity, especially when used as a functional ingredient in foods.

Dose response of whole-grain biomarkers: alkylresorcinols in human plasma and their metabolites in urine in relation to intake

BACKGROUND

Alkylresorcinols (ARs), phenolic lipids almost exclusively present in the outer parts of wheat and rye grains in commonly consumed foods, have been proposed as specific dietary biomarkers of whole-grain wheat and rye intakes.

OBJECTIVE

The objective was to assess the dose response of plasma ARs and the excretion of 2 recently discovered AR metabolites in 24-h urine samples in relation to AR intake and to establish a pharmacokinetic model for predicting plasma AR concentration.

DESIGN

Sixteen subjects were given rye bran flakes containing 11, 22, or 44 mg total ARs 3 times daily during week-long intervention periods separated by 1-wk washout periods in a nonblinded randomized crossover design. Blood samples were collected at baseline, after the 1-wk run-in period, and after each treatment and washout period. Two 24-h urine samples were collected at baseline and after each treatment period.

RESULTS

Plasma AR concentrations and daily excretion of 2 urinary AR metabolites increased with increasing AR dose (P < 0.001). Recovery of urinary metabolites in 24-h samples decreased with increasing doses from approximately 90% to approximately 45% in the range tested. A one-compartment model with 2 absorption compartments with different lag times and absorption rate constants adequately predicted plasma AR concentrations at the end of each intervention period.

CONCLUSION

Both plasma AR concentrations and urinary metabolites in 24-h samples showed a dose-response relation to increased AR intake, which strongly supports the hypothesis that ARs and their metabolites may be useful as biomarkers of whole-grain wheat and rye intakes.

Gas chromatography/tandem mass spectrometry analysis of alkylresorcinols in red blood cells

Erythrocyte alkylresorcinols (5-alkyl-1,3-dihydroxybenzenes) are potential biomarkers of wholegrain wheat and rye intake. However, their high-throughput quantitative analysis by gas chromatography/mass spectrometry (GC/MS) is hindered by the time-consuming sample preparation and, more importantly, by interfering compounds that still remain after sample cleanup. In the present work we describe a gas chromatography/tandem mass spectrometry (GC/MS/MS) method for the rapid and reliable quantification of alkylresorcinols in erythrocyte samples. The performance of the GC/MS/MS method is compared with that of GC/MS. The main characteristics of the method are: lower limits of detection: 2-10 microg/L standard solution; lower limits of quantification: 6-30 microg/L standard solution; linearity coefficients: 0.9611-0.9888; linear ranges: 2-20 microg/L in erythrocytes; and intra-day precisions (n = 6): 4-13% at endogenous analyte levels in non-spiked erythrocytes. Tandem mass spectrometry showed greatly improved selectivity over single-stage mass spectrometry in the case of erythrocyte samples, eliminating all interferences detectable in single-stage MS and enabling simple peak integration for quantification. Moreover, increased selectivity resulted in GC separation speeded up by a factor of two, allowing the duplicate analysis of over 40 samples per day. This GC/MS/MS method is suggested as an improved alternative to GC/MS for the quantification of alkylresorcinols in erythrocytes for assessing wholegrain wheat and rye intake.

Phytochemical and fiber components in oat varieties in the HEALTHGRAIN Diversity Screen

The levels and compositions of a range of phytochemicals (sterols, tocols, avenanthramides, folates, phenolic acids) and dietary fiber components were determined in five oat cultivars (four husked and one naked) grown on a single site in 2005. The total levels of tocols, phenolic acids, and avenanthramides varied by over 2-fold between cultivars, but less variation occurred in total sterols and total folates. Limited variation was also observed in the dietary fiber content and composition of the four husked lines. These results indicate that it may be possible to selectively breed for lines with high contents of dietary fiber and specific groups of phytochemicals.

Phytochemical and dietary fiber components in barley varieties in the HEALTHGRAIN Diversity Screen

Ten different barley varieties grown in one location were studied for their content of tocols, folate, plant sterols, alkylresorcinols, and phenolic acids, as well as dietary fiber components (arabinoxylan and beta-glucan). The samples included hulled and hull-less barley types and types with normal, high-amylose, and waxy starch. The aim was to study the composition of raw materials, and therefore the hulls were not removed from the hulled barleys. A large variation was observed in the contents of all phytochemicals and dietary fibers. Two varieties from the INRA Clermont Ferrand barley program in France (CFL93-149 and CFL98-398) had high content of tocopherols and alkylresorcinols, whereas the variety Dicktoo was highest in dietary fiber content and phenolics. Positive correlations were found between 1000 kernel weight, alkylresorcinols, and tocols, as well as between dietary fiber content and phenolic compounds. The results demonstrate that the levels of phytochemicals in barley can likely be affected by breeding and that the contents of single phytochemicals may easily be adjusted by a right selection of a genotype.

Alkylresorcinols in wheat varieties in the HEALTHGRAIN Diversity Screen

The contents of alkylresorcinols (AR) were analyzed in 131 winter wheats, 20 spring wheats, 10 durum wheats, 5 spelt wheats, and 10 early cultivated forms of wheat (5 diploid einkorn and 5 tetraploid emmer), which are part of the HEALTHGRAIN diversity screen. AR were analyzed by gas chromatography (GC), which provides both total contents and relative homologue compositions, as well as with a Fast Blue colorimetric method that provides only total contents but which is fast and easily screens a large number of samples. There was considerable variation in the total AR content analyzed with GC: winter wheat (220-652 microg/g of dm), spring wheat (254-537 microg/g of dm), durum wheat (194-531 microg/g of dm), spelt (490-741 microg/g of dm), einkorn (545-654 microg/g of dm), and emmer wheat (531-714 microg/g of dm). The relative AR homologue composition was different for different types of wheat, with a C17:0 to C21:0 ratio of 0.1 for winter, spring, and spelt wheats, 0.04 for einkorn and emmer wheat, and 0.01 for durum wheat. The total AR content analyzed with the Fast Blue method was lower than that analyzed with GC but there was a good correlation between the two methods (R(2) = 0.76).

Grevillosides A-F: glucosides of 5-alkylresorcinol derivatives from leaves of Grevillea robusta

From a MeOH extract of leaves of Grevillea robusta, seven compounds (1-7) were isolated. One known compound (7) was identified with a benzyl glucoside, icariside F2. The structures of the six of these, named grevillosides A-F (1-6), were elucidated on detailed inspection of one- and two-dimensional NMR spectroscopic data as glucosides of 5-alkylresorcinols.

Urinary 3-(3,5-dihydroxyphenyl)-1-propanoic acid, an alkylresorcinol metabolite, is a potential biomarker of whole-grain intake in a U.S. population

5-n-Alkylresorcinols (AR) are a major group of phenolic compounds in whole-grain wheat, rye, and barley. As such, they may serve as potential biomarkers of whole-grain intake, because they are quantifiable intact in plasma and as metabolites in urine. We examined relationships between 12-h urinary excretion of AR metabolite 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA) and self-reported habitual intake of whole-grain foods measured by 3-d food record (3DFR) and FFQ. Urine samples from 100 men and women were analyzed for DHPPA using HPLC with coularray detection. DHPPA excretion ranged from 1.3 to 99.4 (mean +/- SE, 14.0 +/- 1.5) mumol/12 h. Whole-grain food intake, as determined by 3DFR and FFQ and adjusted for BMI and energy and fiber intake, was significantly associated with 12-h urinary DHPPA excretion. Based on 3DFR, whole-grain wheat + rye consumers had a 44% higher DHPPA excretion than nonconsumers [ratio of excretion (95% CI) = 1.44 (1.04, 1.97); P = 0.029]. Using whole-grain intake estimated by FFQ, a serving increase in whole-grain wheat + rye intake increased DHPPA excretion by 94% [ratio of excretion (95% CI) = 1.94 (1.35, 2.78); P = 0.001] and a serving increase in whole grains as defined more broadly in epidemiologic studies of whole-grain intake and disease risk (whole-grain wheat, rye, oats, and corn) increased DHPPA by 67% [ratio of excretion (95% CI) = 1.67 (1.28, 2.17); P < 0.0001]. This study supports the potential utility of urinary DHPPA as a biomarker of whole-grain intake in a U.S. population.

Alkylresorcinols in selected Polish rye and wheat cereals and whole-grain cereal products

The alkylresorcinol content and homologue composition in selected Polish rye and wheat cultivars and selected whole-grain cereal products were determined in this study. Cereal grains and whole-grain cereal products were extracted with acetone, whereas bread types were extracted with hot 1-propanol. The average alkylresorcinol content in tested rye (approximately 1100 mg/kg DM) and wheat (approximately 800 mg/kg DM) grains harvested in Poland was within the range previously reported in Swedish and Finnish samples. The total alkylresorcinol content in tested cereal products available on the Polish market varied from very low levels in barley grain-based foods up to 3000 mg/kg DM in wheat bran. The total alkylresorcinol content in 14 bread samples extracted with hot 1-propanol varied from approximately 100 mg/kg DM in whole bread made with honey up to approximately 650 mg/kg DM in whole-rye bread. Calculated ratios of C17:0 to C21:0 homologues, a useful parameter previously used to distinguish between rye and wheat cereals and their derived products, was about 1.2-1.4 in rye products, about 0.2 in wheat products, and varied between 0.2 and 0.6 in cereal-derived products containing a mixture of whole rye and/or wheat. The data set obtained were subsequently compared using cluster and principal component analysis, which allowed the tested cereal products to be classified into two major groups consisting of whole-rye or whole-wheat products, respectively. On the basis of that approach, mixed cereal products containing rye and wheat bran or whole rye and wheat flour were grouped between those two well-defined clusters. Our work not only provides a detailed examination of alkylresorcinols in selected Polish rye and wheat cultivars and selected whole-grain cereal products, but also demonstrates that this type of analysis accompanied by the use of proper statistical algorithms offers an objective way to evaluate the quality of whole-grain rye and/or wheat and their derived products.

Alkylresorcinols as biomarkers of whole-grain wheat and rye intake: plasma concentration and intake estimated from dietary records

BACKGROUND

Alkylresorcinols (ARs), phenolic lipids exclusively present in the outer parts of wheat and rye grains, have been proposed as specific dietary biomarkers of whole-grain wheat and rye intake.

OBJECTIVE

The objective was to validate plasma ARs as a biomarker of whole-grain wheat and rye intakes by studying the correlation between their plasma concentration and intake calculated from food records.

DESIGN

In a randomized crossover study, 22 women and 8 men were given a defined amount of either whole-grain or refined-cereal-grain products to be included in their habitual diets for two 6-wk periods. Blood samples were collected and food intakes were recorded before and after each intervention period.

RESULTS

Plasma AR concentrations were significantly higher after the whole-grain diet period than after the refined-grain period (P < 0.0001) and were well correlated with average daily AR intake estimated by self-reported weighed food records (Spearman's r = 0.58, P < 0.001).

CONCLUSION

Plasma AR concentrations are correlated with intake assessed by food records, which suggests that ARs are selective nutritional biomarkers for the intake of whole-grain wheat and rye.

Very long chain alkylresorcinols accumulate in the intracuticular wax of rye (Secale cereale L.) leaves near the tissue surface

Alkylresorcinols (ARs) are bioactive compounds occurring in many members of the Poaceae, likely at or near the surface of various organs. Here, we investigated AR localization within the cuticular wax layers of rye (Secale cereale) leaves. The total wax mixture from both sides of the leaves was found to contain primary alcohols (71%), alkyl esters (11%), aldehydes (5%), and small amounts (<3%) of alkanes, steroids, secondary alcohols, fatty acids and unknowns. A homologous series of ARs (3%) was identified by GC-MS and comparison with a synthetic standard of nonadecylresorcinol. The alkyl side chains of the wax ARs contained odd numbers of carbons ranging from C19 to C27, with a prevalence of C21, C23 and C25. Waxes from both sides of the leaf, analyzed separately in a second experiment, comprised the same compound classes in similar relative amounts and with similar homolog patterns. Finally, the epicuticular and intracuticular wax layers were sampled separately from the abaxial side of the leaf. While ARs accounted for 2% of the intracuticular wax, they were not detectable in the epicuticular wax. The intracuticular wax was also slightly enriched in steroids, whereas the epicuticular layer contained more primary alcohols. All other wax constituents were distributed evenly between both wax layers.

Profiling of Alk(en)ylresorcinols in cereals by HPLC-DAD-APcI-MSn

5-Alk(en)ylresorcinols in rye, wheat, spelt, and barley have been characterized by high-performance liquid chromatography coupled to atmospheric pressure chemical ionization multistage mass spectrometry (HPLC-APcI-MS(n)) for the first time. Among the 29 compounds analysed, several major and minor C(15), C(17), C(19), C(21), C(23), and C(25)-substituted resorcinols with saturated, monoenoic, dienoic, and/or oxygenated side-chains were characterized by their specific fragmentation patterns in collision-induced dissociation experiments. Additionally, a C(27:0) homologue, which has probably been overlooked in previous studies based on HPLC alone, was detected in all cereals analysed. Furthermore, we provide tentative evidence for the occurrence of alkylresorcinols with triolefinic side-chains, which have, to our knowledge, so far not been reported in any cereal species.

Inhibitory effect of some natural and semisynthetic phenolic lipids upon acetylcholinesterase activity

The effect of phenolic lipids isolated from rye grains and cashew nut shell liquid (CNSL) from Anacardium occidentale and their semisynthetic derivatives on erythrocyte ghost's acetylcholinesterase activity was studied. It has been shown that all tested compounds decreased the enzymatic activity of acetylcholinesterase. This effect depends on the type of studied compounds. Three of them completely inhibit acetylcholinesterase activity at the micromolar concentration.