Alkylresorcinols in Swedish cereal food products

Human Intervention Study: Alkylresorcinol Metabolites as Potential Biomarkers for Grain Intake and the Occurrence of Alkylresorcinols in Commonly Consumed Foods in the German Retail Sector

Grains are one of the primary nutrients and are associated with many health benefits. To reflect the intake of grain-based products, two promising potential biomarkers are alkylresorcinol (AR) metabolites 3,5-dihydroxybenzoic acid (3,5-DHBA) and 3-(3,5-dihydroxyphenyl)-propanoic acid (3,5-DHPPA). The aim of this study was to validate the occurrence of AR in food samples and investigate the suitability of their metabolites as potential biomarkers in human intervention studies. In the first step, the AR content in different grain products from the German retail sector was analyzed by GC-MS. ARs were found in higher concentrations in whole grain products and in moderate contents in refined grains and quinoa. Based on these results, human intervention studies were performed in the next step, and the AR metabolites 3,5-DHBA and 3,5-DHPPA were analyzed by LC-MS/MS in urine samples. The intake of only whole grain products leads to an increasing level of both potential biomarkers, while a refined grain diet shows decreasing levels of the AR metabolites. The excretion of 3,5-DHBA after a whole grain-rich diet differs significantly (p = 0.043) from no grain intake.

High-throughput multitarget quantitative assay to profile the whole grain-specific phytochemicals alkylresorcinols, benzoxazinoids and avenanthramides in whole grain and grain-based foods

Currently, there is a growing interest in using whole grain (WG)-specific phytochemicals to perform WG research, including research on dietary assessment, health mechanisms, and quality control. However, the current approaches used for WG-specific phytochemical analysis cannot simultaneously achieve coverage, specificity, and sensitivity. In the present study, a series of WG-specific phytochemicals (alkylresorcinols (ARs), benzoxazinoids (BXs) and avenanthramides (AVAs)) were identified, and their mass spectrometry (MS) fragmentation mechanism was studied by TOF MS. Based on diagnostic fragmentation ions and retention time prediction models, a LC-MS/MS method was developed. Through this method, 56 ARs, 13 BXs, and 19 AVAs in WGs and grain-based foods were quantified for the first time. This method was validated and yielded excellent specificity, high sensitivity and negligible matrix effects. Finally, we established WG-specific phytochemical fingerprints in a variety of WG and grain-based foods. This method can be used for WG quality control and WG precision nutrition research.

Non-Destructive Determination of Alkylresorcinol (ARs) Content on Wheat Seed Surfaces and Prediction of ARs Content in Whole-Grain Flour

Alkylresorcinols (ARs) are beneficial for human health and can be used as biomarkers for whole-grain cereal intake. In previous studies, ARs content in whole-grain flour was determined by milling the seeds into powder, thus destroying their structure. In this paper, we adopted a non-destructive extraction approach. Chloroform and ethyl acetate extraction methods were carried out to extract lipids from the seed surface and whole-grain flour of 36 wheat varieties in China, respectively. GC-MS analysis identified chemical compounds in which ARs were the major compounds for all the samples. The average total content of ARs (624.223 µg/g) in whole grains was much higher than that on seed surfaces (4.934 µg/g), with a positive correlation (r = 0.863, p < 0.001) between these two parameters. The results suggested that the total ARs content on the seed surface can be used to predict their content in whole-grain flour. Without affecting the seed germination rate and damaging seed structure, we demonstrate that a non-destructive extraction approach is an appropriate and useful method, facilitating the development of rapid screening methods suitable for use in wheat breeding.

Long-Term Whole Grain Wheat and Rye Intake Reflected by Adipose Tissue Alkylresorcinols and Breast Cancer: A Case-Cohort Study

Whole grain rye (WGR) and whole grain wheat (WGW) have been suggested to protect against the development of breast cancer. In this study, we estimated long-term intake of WGR and WGW, using both a food frequency questionnaire (FFQ) and alkylresorcinol concentrations in adipose tissue biopsies, in relation to the risk of developing invasive breast cancer in a case-cohort study (n = 414 in the case group, n = 933 in the subcohort group) on the Danish “Diet, Cancer and Health” cohort. The median follow-up time of the subcohort was 5.3 years. Total WGR and WGW intake estimated with FFQ or reflected by total alkylresorcinol concentration in adipose tissue was not significantly associated with risk of breast cancer. However, after adjustment for total WGR and WGW intake, women in the highest quartile of relative WGR intake, reflected by the alkylresorcinol C17:0/C21:0 ratio, had a higher risk of overall breast cancer and estrogen-receptor-positive (ER+) breast cancer than women in the lowest quartile of relative WGR intake, while the risk of estrogen-receptor-negative (ER-) breast cancer incidence was unaffected. Similar results were obtained with the FFQ data. Based on these data, further investigation of the role of specific grain types in reducing or increasing breast cancer risk, and their overall impact on health, is warranted.

Targeted Metabolite Profiling-Based Identification of Antifungal 5-n-Alkylresorcinols Occurring in Different Cereals against Fusarium oxysporum

A rapid and convenient biochemometrics-based analysis of several cereal-derived extracts was used to identify n-alkyl(enyl)resorcinols (AR) as antifungals against Fusarium oxysporum. Total AR content and liquid chromatography/mass spectrometry (LC-MS)-based profiles were recorded for each extract, in addition to their antifungal activity, to help integrate these chemical and biological datasets by orthogonal partial least squares regression. In this study, we developed and used a micro-scale amended medium (MSAM) assay to evaluate the in vitro mycelial growth inhibition at low amounts of extracts. Triticale husk-derived extracts had the highest AR content (662.1 µg olivetol equivalent/g dry extract), exhibiting >79% inhibition at the highest doses (10.0–1.0 µg/µL). Correlation of the chemical and antifungal datasets using supervised metabolite profiling revealed that 5-n-nonadecanylresorcinol, 5-n-heneicosylresorcinol, and 5-n-tricosyl-resorcinol were the most active ARs occurring in cereal products from Colombia. Hence, we propose the biochemometrics-based approach as a useful tool for identifying AR-like antifungals against F. oxysporum.

Evaluation of alkylresorcinols in adipose tissue biopsies as a long-term biomarker of whole-grain wheat and rye intake in free-living Swedish men and women

OBJECTIVE

Wheat and rye, the most consumed whole grains (WG) in the Nordic countries, contain alkylresorcinols (AR) in their bran. AR concentrations in human adipose tissue might reflect long-term WG rye and wheat intake. We aimed to evaluate AR concentrations in adipose tissue biopsies as a long-term biomarker of WG wheat and rye intake in free-living Swedish men and women.

DESIGN

Cross-sectional study. AR concentrations in adipose tissue biopsies were analysed and compared with long-term WG intake assessed by three FFQ (repeated over a period of 14 years in men, 17 years in women) and with plasma AR concentrations.

SETTING

The Cohort of Swedish Men between 1997 and 2010 and the Swedish Mammography Cohort between 1987 and 2003, Sweden.

SUBJECTS

Men (n 149) and women (n 109).

RESULTS

Long-term WG rye intake estimated with repeated FFQ correlated (r=0·31-0·41, P<0·01) with adipose-tissue AR concentrations, while WG wheat intake correlated only weakly (r=0·17-0·33, P<0·05). Total AR concentration in adipose tissue was 61 % lower in women than in men at similar energy-adjusted WG wheat and rye intakes, but plasma concentrations were similar. AR concentrations in adipose tissue correlated well with plasma concentrations (r=0·49-0·81, P<0·001).

CONCLUSIONS

AR in adipose tissue reflected long-term WG rye but not WG wheat intake, probably due to poor precision in estimating WG wheat intake by FFQ. AR in adipose tissue appears promising as a biomarker of long-term WG rye intake but should be adjusted for sex.

Novel urinary alkylresorcinol metabolites as biomarkers of whole grain intake in free-living Swedish adults

SCOPE

Most studies on the role of whole grain for health rely on self-reported intake data, which are prone to measurement errors. There is a need for dietary biomarkers that can provide an objective measure of intake. Alkylresorcinols (AR) and their main metabolites 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-propanoic acid (DHPPA) have been proposed as biomarkers for whole grain (WG) wheat and rye intake.

METHODS AND RESULTS

The medium-term reproducibility and relative validity of four putative urinary AR metabolites (3,5-dihydroxycinnamic acid (DHCA), 5-(3,5-dihydroxyphenyl) pentanoic acid (DHPPTA), 2-(3,5-dihydroxybenzamido)acetic acid (DHBA-glycine) and 3,5-dihydroxycinnamic acid amide (DHCA-amide)) as biomarkers for WG intake were investigated. Three-day weighed food records and 24-h urine samples from two occasions 2-3 months apart were obtained from 69 Swedish adults. WG intake was calculated and urinary AR metabolites were analyzed. The medium-term reproducibility determined for DHCA, DHPPTA, and DHBA-glycine varied from moderate-to-excellent (intra-class correlation coefficient = 0.63-0.85). Moreover, DHCA and DHPPTA excretion correlated well with self-reported total WG intake (r = 0.55, p < 0.001 and r = 0.42, p < 0.001, respectively).

CONCLUSION

DHCA or DHPPTA excretion in 24-h urine might be a suitable medium- to long-term biomarker of WG wheat and rye intake. These findings need to be confirmed in populations with low and infrequent WG intake.

The whole grain content of foods consumed in the UK

This study aimed to assess the whole grain (WG) content of foods consumed in the UK which include ingredients that retain all three structural components of the grain, and contained ⩾10% WG. Dietary data from seven studies with 10,474 UK subjects were examined for foods containing WG. The WG content was then determined from ingredient lists, manufacturers' information and recipes. 372 food descriptors from nine food groups (4.4% of all food codes) contained ⩾10% WG. Of these 372 foods, 31.5% contained ⩾51%, 30.6% 25-50%, and 37.9% 10-24% WG dry matter as eaten. The relatively small number of WG foods identified in the total number of foods consumed confirms the low contribution of WG foods to the overall pattern of foods consumed in the UK. Since foods containing <51% WG accounted for the majority of WG food codes identified, recognising the importance of these foods to WG intake is essential.

Validation of Reported Whole-Grain Intake from a Web-Based Dietary Record against Plasma Alkylresorcinol Concentrations in 8- to 11-Year-Olds Participating in a Randomized Controlled Trial

BACKGROUND

Whole-grain (WG) intake is important for human health, but accurate intake estimation is challenging. Use of a biomarker for WG intake provides a possible way to validate dietary assessment methods.

OBJECTIVE

Our aim was to validate WG intake from 2 diets reported by children, using plasma alkylresorcinol (AR) concentrations, and to investigate the 3-mo reproducibility of AR concentrations and reported WG intake.

METHODS

AR concentrations were analyzed in fasting blood plasma samples, and WG intake was estimated in a 7-d web-based diary by 750 participants aged 8-11 y in a 2 school meal × 3 mo crossover trial. Reported WG intake and plasma AR concentrations were compared when children ate their usual bread-based lunch (UBL) and when served a hot lunch meal (HLM). Correlations and cross-classification were used to rank subjects according to intake. The intraclass correlation coefficients (ICCs) between subjects' measurements at baseline and after the UBL were used to assess reproducibility.

RESULTS

Correlations between reported WG wheat + rye intake and plasma AR were 0.40 and 0.37 (P < 0.001) for the UBL and the HLM diets, and 78% and 77% were classified in the same or adjacent quartiles for the UBL and HLM diets, respectively. The ICC over 3 mo was 0.47 (95% CI: 0.38, 0.55) for plasma total ARs and 0.64 (95% CI: 0.58, 0.70) for reported WG intake. Correlations were higher when using the AR C17:0 homolog as a biomarker, reflecting rye intake instead of plasma total ARs [UBL: r = 0.47; HLM: r = 0.43, P < 0.001; ICC = 0.51 (95% CI: 0.43, 0.59)].

CONCLUSIONS

Self-reported WG wheat + rye intake among children showed moderate correlations with plasma AR concentrations. Substantial intraindividual variation was found in WG intake and plasma AR concentrations. The AR homolog C17:0 may be used as a biomarker for WG intake when the WG intake primarily comes from rye as in the present study. This trial was registered at clinicaltrials.gov as NCT01457794.

Analysis of phenolic and cyclic compounds in plants using derivatization techniques in combination with GC-MS-based metabolite profiling

Metabolite profiling has been established as a modern technology platform for the description of complex chemical matrices and compound identification in biological samples. Gas chromatography coupled with mass spectrometry (GC-MS) in particular is a fast and accurate method widely applied in diagnostics, functional genomics and for screening purposes. Following solvent extraction and derivatization, hundreds of metabolites from different chemical groups can be characterized in one analytical run. Besides sugars, acids, and polyols, diverse phenolic and other cyclic metabolites can be efficiently detected by metabolite profiling. The review describes own results from plant research to exemplify the applicability of GC-MS profiling and concurrent detection and identification of phenolics and other cyclic structures.

Plasma alkylresorcinols, biomarkers of whole-grain wheat and rye intake, and incidence of colorectal cancer

BACKGROUND

Few studies have investigated the association between whole-grain intake and colorectal cancer. Because whole-grain intake estimation might be prone to measurement errors, more objective measures (eg, biomarkers) could assist in investigating such associations.

METHODS

The association between alkylresorcinols, biomarkers of whole-grain rye and wheat intake, and colorectal cancer incidence were investigated using prediagnostic plasma samples from colorectal cancer case patients and matched control subjects nested within the European Prospective Investigation into Cancer and Nutrition. We included 1372 incident colorectal cancer case patients and 1372 individual matched control subjects and calculated the incidence rate ratios (IRRs) for overall and anatomical subsites of colorectal cancer using conditional logistic regression adjusted for potential confounders. Regional differences (Scandinavia, the Mediterranean, Central Europe) were also explored.

RESULTS

High plasma total alkylresorcinol concentration was associated with lower incidence of distal colon cancer; the adjusted incidence rate ratio of distal colon cancer for the highest vs lowest quartile of plasma total alkylresorcinols was 0.48 (95% confidence interval [CI] = 0.28 to 0.83). An inverse association between plasma total alkylresorcinol concentrations and colon cancer was found for Scandinavian participants (IRR per doubling = 0.83; 95% CI = 0.70 to 0.98). However, plasma total alkylresorcinol concentrations were not associated with overall colorectal cancer, proximal colon cancer, or rectal cancer. Plasma alkylresorcinols concentrations were associated with colon and distal colon cancer only in Central Europe and Scandinavia (ie, areas where alkylresorcinol levels were higher).

CONCLUSIONS

High concentrations of plasma alkylresorcinols were associated with a lower incidence of distal colon cancer but not with overall colorectal cancer, proximal colon cancer, and rectal cancer.