Alkylresorcinols Research Articles

Hepatic biotransformation of alkylresorcinols is mediated via cytochrome P450 and β‐oxidation.

Alkylresorcinols (AR) are phenolic lipids present in the bran of whole grains, particularly in wheat and rye kernels. AR may serve as a biomarker of whole grain intake. While AR pharmacokinetics and principal end metabolites have been reported, the metabolic pathways contributing to their relatively rapid elimination from the circulation remain to be established. We investigated whether hepatic ω‐ and β‐oxidation mediate the catabolism of the AR homolog C19:0 to form 3,5‐dihydroxybenzoic acid and 3‐(3,5‐dihydroxyphenyl)‐1‐propanoic acid (DHPPA) using 3 in vitro platforms: human recombinant cytochrome P450 4F2 (CYP4F2), human liver S9 fraction (which includes microsomal and cytosolic enzymes), and HepG2 cells. After incubation with 10 μmol/L C19:0, one hydroxylated metabolite was formed by CYP4F2 and its production appeared to plateau after 1.0 h. After incubation of 10 μmol/L C19:0 with human S9 for up to 4 h, one hydroxylated and one carboxylated metabolite were identified, with their production increasing linearly with time. When HepG2 cells were treated with 5, 10, or 25 μmol/L C19:0 for 48 h, DHPPA was excreted into the media in a dose‐dependent manner. Our results are consistent with a metabolic pathway of absorbed AR to phenolic acids via CYP4F2‐mediated ω‐hydroxylation. Funded by the General Mills Inc. and USDA.

Oat usage in food production as a bioactive component source

Despite oats’ early acceptance, the crop became widely accepted only as animal fodder. Having more nutritional value and functional properties, in recent years oats and oat products started to use for human diet. Oat is useful for the control of diabetes, lipid profile, total and low density lipoprotein (LDL) cholesterol levels. Oat grain contains high amounts of dietary fiber (DF), especially β‐glucan. The antioxidant potential of oats has also been recognized for many years. Ferulic and caffeic acid derivatives were proposed to be the source of the antioxidant activity of oat. Phenolic acids, alk(en)ylresorcinols, and avenanthramides are phenolic compounds typically found in grain products, with avenanthramides only in oats. Antioxidants can also provide health benefits against those free radicals in vivo associated with membrane damage, aging, heart disease, and cancer in humans. These all nutritional and functional benefits attributed to dietary fiber, β‐glucan and phenolic compounds have recently greatly increased interest in oat as a human food. In this review, nutritional and functional properties and health benefits of oat products have been briefly discussed.

Determination of association constants between 5′-guanosine monophosphate gel and aromatic compounds by capillary electrophoresis

Hydro gel formed by 5′-guanosine monophosphate (GMP) in the presence of a potassium ion is expected to exhibit interesting selectivity in capillary electrophoretic separations. Here, we estimated the conditional association constants between the hydro gel (G-gel) and aromatic compounds by capillary electrophoresis in order to investigate the separation selectivity that is induced by the G-gel. Several aromatic compounds were separated in a solution containing GMP and potassium ion at different concentrations. The association constants were calculated by correlating the electrophoretic mobilities of the analytes obtained experimentally using a concentration of G-gel. During semi-quantitative estimation, naphthalene derivatives had larger association constants (Kass=10.3–16.8) compared with those of benzene derivatives (Kass=3.91–5.31), which means that the binding sites of G-gel match better to a naphthalene ring than to a benzene ring. A hydrophobic interaction was also found when the association constants for alkyl resorcinol were compared with those of different hydrocarbon chains. The association constants of nucleobases and tryptophan ranged from 6.05 to 12.6, which approximated the intermediate values between benzene and naphthalene derivatives. Consequently, the selective interaction between G-gel and aromatic compounds was classified as one of three types: (1) an intercalation into stacked planar GMP tetramers; (2) a hydrophobic interaction with a long alkyl chain; or, (3) a small contribution of steric hindrance and/or hydrogen bonding with functional groups such as amino and hydroxyl groups.

Computer-aided design of selective Cytochrome P450 inhibitors and docking studies of alkyl resorcinol derivatives

The present investigation is aimed to understand the interactive mechanism that occurs between the active site of Cytochrome P450 and its inhibitors by molecular modeling studies. Based on the docking studies and information obtained from interaction analysis, structure-based virtual screening was performed by selecting 217 new potential inhibitors with structural diversity using GOLD and ArgusLab molecular docking softwares. Among a total of 217 compounds, only 21 molecules were considered as the potential inhibitors. Hydrogen bond and van der Waals interaction between various active site residues like ARG 382, HIS447, CYS449, ASN493, TYR131, and TYR92 of Cytochrome P450 were observed. Docking studies of selected resorcinols showed an optimal molecular environment which is required to bind with active sites of Cytochrome P450. Hydroxyl groups of resorcinols exhibited van der Waals interactions with certain active sites. To estimate the drug-likeness properties the parameters like partition coefficient (log P), tabulated molecular polar surface area (TPSA), and bio activity score were obtained from the Molinspiration studies. Based on docking and Molinspiration data analysis, the molecules 10, 3, 18, 19, and 7 were found to be highly potent inhibitors of Cytochrome P450.

Hepatic biotransformation of alkylresorcinols is mediated via cytochrome P450 and β-oxidation: A proof of concept study

Alkylresorcinols (AR) are phenolic lipids present in the bran of some cereals. AR may serve as a biomarker for whole grain wheat and rye intake. While AR pharmacokinetics and two major metabolites have been reported, the metabolic pathways contributing to their relatively rapid elimination from the circulation remain to be speculative. In this study, we investigated if ω- and β-oxidation mediate catabolism of the AR homologue C19:0 to form 3,5-dihydroxybenzoic acid and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA), using 3 in vitro platforms, human cytochrome P450 4F2 (CYP4F2), human liver S9, and HepG2 cells. One hydroxylated C19:0 metabolite was formed by CYP4F2 and one hydroxylated and one carboxylated C19:0 were tentatively identified after incubation of AR with S9. The formation of DHPPA was quantifiable when HepG2 cells were treated with C19:0 for 48h. Our results are consistent with a metabolic pathway by which AR are degraded to phenolic acids via CYP4F2-mediated ω-oxidation and subsequent β-oxidation.

Effects of region and cultivar on alkylresorcinols content and composition in wheat bran and their antioxidant activity

This study evaluated the effects of cultivar and region on the composition of alkylresorcinols (ARs) of 24 wheat bran samples from 6 cultivars grown in four locations (Bath, Nairn, Palmerstone and Ridgetown) in Ontario (ON), Canada, using gas chromatography/mass spectrometry (GC/MS). Total phenolic content (TPC) of wheat bran extracts was determined by the Folin–Ciocalteau method and the antioxidant activity of wheat bran extracts was measured by 2, 2-Dipheny-1-picryhydrazyl radical (DPPH) scavenging activity and oxygen radical absorbance capacity (ORAC). The highest ARs content (μg/g) was found in cultivars Emmit (1522), Harvard (1305), Warthog (1170), and Superior (853), grown in Ridgetown. The relative saturated and unsaturated ARs (%) were 89 and 11, respectively. Total ARs content, their composition, TPC and antioxidant activity of wheat bran extracts were significantly (P < 0.05) affected by location and cultivar and their interaction. TPC, %DPPHdis, and ORAC values for different wheat bran sample extracts ranged from 3 to 58 (mg FAE/g), 5 to 68 (%), and 6 to 94 (μmol TE/g), respectively. Our work provides a detailed examination of region and cultivar effects on potential of ARs in wheat bran and the results can be used for screening and breeding purposes.

Long-term reproducibility of plasma alkylresorcinols as biomarkers of whole-grain wheat and rye intake within Northern Sweden Health and Disease Study Cohort

Alkylresorcinols (AR) have been suggested as specific biomarkers of whole-grain (WG) and bran intake from wheat and rye. Before using plasma AR as biomarkers in prospective cohort studies, the long-term reproducibility needs to be determined in order to judge how well a single plasma sample reflects the long-term concentration. The objective was therefore to estimate the reproducibility of plasma AR concentrations over 0.1-3.9 years. The concentrations of AR homologues were analysed in plasma samples, drawn>8 h since last meal, 0.1-3.9 years apart (mean ≈ 2 years) in 74 participants in the Swedish prospective Västerbotten Intervention Project cohort. Reproducibility was estimated by calculating the intra class correlation coefficient (ICC). Fasting plasma AR concentrations were similar between the first and second measurements. The ICC for total AR was 0.54 (95% confidence interval (CI)=0.38-0.69] overall, 0.34 (95% CI=0.13-0.64) for men and 0.73 (95% CI=0.56-0.85) for women, respectively. Somewhat higher ICCs were obtained for shorter AR homologues. In summary, the reproducibility of plasma AR over 0.1-3.9 years was high for women and moderate for men within this population. Together with previous data showing high validity of plasma AR as biomarkers of wheat and rye in different populations, the current finding suggest that this biomarker is stable over a long-time period and is therefore probably useful for assessment of long-term WG intake in populations with a wide intake range and a frequent intake.

ALK(EN)YLRESORCINOL CONCENTRATIONS IN 'KENSINGTON PRIDE' MANGO PEEL AND ANTIFUNGAL ACTIVITY AGAINST COLLETOTRICHUM GLOEOSPORIOIDES

Two preformed alk(en)ylresorcinols, 5-n-heptadecenylresorcinol and 5-n-pentadecylresorcinol, were identified in ‘Kensington Pride’ mango fruit peel. The alk(en)ylresorcinols had antifungal activity against C. gloeosporioides, as determined from thin layer chromatography bioassays. Soil-applied activators of plant defence (Acibenzolar at 150 mg L-1, and soluble potassium silicate at 200 and 1000 mg L-1) did not influence concentrations of 5-n-heptadecenylresorcinol or 5-n-pentadecyl¬resorcinol in mango peel when applied 2 months after fruit set and one month later. Concentrations of both alk(en)ylresorcinols were high 2 months after fruit set but levels declined by 50% within 1 month (2 months before commercial harvest) and did not change significantly from commercial harvest until eating-ripe.

Stability and antioxidant activity of alkyresorcinols in breads enriched with hard and soft wheat brans

Alkylresorcinols (ARs) are phenolic lipids that are mostly found in rye and wheat brans. In this study, the stability of AR content and homologue composition of hard red wheat bran (HRWB) and soft red wheat bran (SRWB) were studied, using four different bread formulations. ARs in wheat bran samples were extracted with four different solvents whereas ARs in breads were extracted with hot 1-propanol and quantified using gas chromatography–mass spectrometry (GC/MS). The different formulas used in four bread trial were: A) 100% white flour (control breads), B) 30% wheat bran, C) 30% residue bran after AR extraction, and D) 30% wheat bran plus 2% crude AR extract. AR content in breads varied from 1.1 to 82.9mg/100g and showed that they were heat stable during baking. After 1h cooling, all breads showed significantly different (P<0.05) inner temperature, height and weight compared to control bread. Furthermore, bread D showed a better height than breads B and C (P<0.05). The effects of baking on total phenolic content (TPC) and antioxidant activity were also determined. A positive correlation was observed between oxygen radical absorbance capacity (ORAC) and TPC (R2=0.89).

Alkylresorcinols isolated from rye bran by supercritical fluid of carbon dioxide and suspended in a food-grade emulsion show activity against Penicillium expansum on apples

Apple cultivars are attacked by many fungal diseases, both on the tree and during storage. One of the most serious is blue mould, caused by Penicillium expansum. In this study, 5-(n)-alkylresorcinols (AR) were isolated from rye bran by the supercritical fluid of carbon dioxide and were used for the preparation of bioactive emulsions. These emulsions were applied to harvested fruit of five apple varieties to determine the levels of antifungal activity. A significant inhibition of disease symptoms was obtained after spraying some of the prepared AR emulsions on fruits that had been experimentally infected with Penicillium expansum. The most effective emulsions consisted of 0.025% (m/v) ARs, 0.1% (m/v) xanthan gum, 0.5% (m/v) Synperonic 91/6 or PDMs-copolymer, 0.2% (m/v) Tween 20, 1% (m/v) Trioleate, 2% (m/v) oleylalcohol, 2% (m/v) PEG 400, 5% (m/v) CaCl2 or NaCl suspended in water.

Inhibition of wheat bran and it′s active compoments on α-glucosidase in vitro

Background:Wheat bran is a traditional Chinese medicine; however, it is mostly used as feedstuff in China. Wheat bran is widely accepted as an important ingredient in many low-glycemic index foods in modern western societies; however, its glycemic control mechanism is unknown.Objective:To determine potent α-glucosidase inhibitory compounds from wheat bran and to identify the inhibition on α-glucosidase.Materials and Methods:Ethanolic extract of wheat bran was prepared to evaluate the inhibitory activity on α-glucosidase, then fractionation of the extract was guided by in vitro enzyme-inhibition assay, and the potent α-glucosidase inhibitory compounds were identified by high performance liquid chromatography and atmospheric pressure chemical ionization-mass spectrometry; finally the enzyme inhibition process was studied using the Michaelis-Menton and the Lineweaver-Burk equations.Results:Both baker's yeast and rat intestinal enzymes were mostly inhibited (87.9% and 66.8% inhibition, respectively) at concentration 0.6 mg/mL of the ethanolic extract of wheat bran. The petroleum ether fraction in the ethanolic extract of wheat bran showed significant activity against rat intestinal α-glucosidase, and revealed a dose-dependent effect. The inhibition was 76.57% at 0.3 mg/mL and 100% at 0.6 mg/mL. The active fraction 13 of petroleum ether fraction was identified as alkylresorcinols (ARs). ARs showed strong inhibition towards α-glucosidase and its IC50 value was found to be 37.58 μg/mL. The enzyme kinetic studies showed that, in the presence of ARs, the Michaelis-Menton constant (Km) remains constant whereas the maximal velocity (Vmax) decreases, revealing a non-competitive type of inhibition.Conclusion:The therapeutic potentiality of ARs in the management of the postprandial hyperglycemia will proliferate the utilization of wheat bran in controlling type 2 diabetes.

Homoserine Lactones and Resorcinolic Lipids Inhibit In vitro Pro-and Anti-inflammatory Cytokine Production

Homoserine Lactones and Resorcinolic Lipids Inhibit In vitro Pro-and Anti-inflammatory Cytokine Production

Alkylresorcinols in Swedish cereal food products

In this study alkylresorcinol (AR) content and homologue composition was determined in 159 cereal products commonly consumed in Sweden. Food items were sorted into seven groups including soft bread, crisp bread, breakfast cereals, pasta, flour, cookies and other cereal products with varying content of rye, wheat, oat, corn, rice and maize. The analyzed total AR content ranged from not detectable to 4178μg/g (fresh weight). Bran and whole grain (WG) items showed highest AR contents and were comparable to previous reports. The AR content was strongly correlated with WG content from rye and wheat cereals (r=0.80, P<0.001), the main source of AR. In addition, the calculated ratio of the homologues C17:0 and C21:0, which was previously reported to distinguish between rye and wheat products, was associated to the proportion of rye content in WG of wheat and rye (r=0.83, P<0.001). The data from the present study can be used to estimate AR intake from WG of rye and wheat in the Swedish population and the results indicated that WG content from rye and wheat may be predicted by using AR content and homologue composition in cereal products.

Synthesis and Inhibitory Activities against Colon Cancer Cell Growth and Proteasome of Alkylresorcinols

We have identified alkylresorcinols (ARs) as the major active components in wheat bran against human colon cancer cell growth (HCT-116 and HT-29) using a bioassay-guided approach. To further study the structure-activity relationships, 15 ARs and their intermediates (1-15) were synthesized expediently by the modified Wittig reaction in aqueous media, and six 5-alkylpyrogallols and their analogues (16-21) were prepared by the general Grignard reaction. The synthetic AR analogues were evaluated for activities against the growth of human colon cancer cells HCT-116 and HT-29 and the chymotrypsin-like activity of the human 20S proteasome. Our results found that (1) AR C13:0 and C15:0 (13 and 14) had the greatest inhibitory effects in human colon cancer cells HCT-116 and HT-29, while decreasing or increasing the side chain lengths diminished the activities; (2) two free meta-hydroxyl groups at C-1 and C-3 on the aromatic ring of the AR analogues greatly contributed to their antitumor activity; (3) the introduction of a third hydroxyl group at C-2 (20 and 21) into the aromatic ring of the AR analogues yielded no significant enhancement in activity against HCT-116 cells and decimated the effects against HT-29 cells, but dramatically increased the activity against the chymotrypsin-like activity of the human 20S proteasome; and (4) AR C11:0 (12) was found to have the greatest effect in a series of AR C9:0-C17:0 against the chymotrypsin-like activity of the human 20S proteasome.

Alkylresorcinol Metabolism in Swedish Adults Is Affected by Factors Other Than Intake of Whole-Grain Wheat and Rye ,

The urinary alkylresorcinol (AR) metabolites, 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-propanoic acid (DHPPA), could potentially serve as biomarkers for intake of whole-grain (WG) wheat and rye. Excretion of AR metabolites is largely dependent on the intake of AR but may also be influenced by other factors. This study aimed to investigate the validity of free and conjugated AR metabolites as biomarkers for WG intake of wheat and rye and to identify potential determinants of AR metabolites in urine. We quantified free aglycones and conjugates of AR metabolites in 24-h urine collections from 52 free-living Swedish adults and calculated correlation coefficients between urinary AR metabolite excretion and self-reported WG intake. We used partial least-squares regression to identify possible determinants of urinary AR metabolites. Approximately 50% of urinary AR metabolites were found as conjugates. Excretions of individually quantified free and conjugated AR metabolites and their sums were correlated to self-reported intake of WG rye and wheat (r = 0.500.68; P < 0.001). Excretion of urinary AR metabolites was mainly dependent on intake of 2 major dietary AR homologs, C19:0 and C21:0. Sex, BMI, and vitamin C intake were identified as determinants of the proportion of free and glucuronidated DHPPA in the present study. Urinary AR metabolites may be useful in reflecting short-term to medium-term intake of WG, but urine samples should be deconjugated prior to quantification. Anthropometric and dietary factors affecting the proportion of conjugated AR metabolites in urine may to some extent influence AR elimination and thereby the performance of urinary AR metabolites as biomarkers.

Alkylresorcinols in Latvian and Finnish breads

The alkylresorcinol (AR) content and relative homologue composition were determined in 9 Latvian and 11 Finnish soft breads. ARs were extracted with hot 1-propanol and quantified, using a gas chromatography-mass spectrometry method. The total AR content (μg/g dry matter) varied from 560 to 840 in rye breads, from 500 to 700 in Finnish mixed rye and wheat flour breads, from 200 to 300 in Latvian mixed rye and wheat flour breads and from 25 to 30 in white wheat breads. Rye and white wheat breads in the two countries varied only slightly in AR content, but there were wide variations in AR content in mixed flour breads. The AR contents in soft breads could be indicators of bran or fibre content, but not of whole-grain flour content.

Reliability of fasting plasma alkylresorcinol metabolites concentrations measured 4 months apart

Alkylresorcinols (AR) have been suggested as specific dietary biomarkers of whole-grain wheat and rye intake. AR are metabolised to 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA), which have longer apparent half-lives and were recently proposed to better reflect long-term whole-grain consumption than the intact AR. The objective of this study was to analyse the reliability--expressed by the intraclass correlation coefficient (ICC)--of AR metabolite concentrations among 100 participants from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study who provided two fasting plasma samples 4 months apart. DHBA and DHPPA concentrations were not significantly different between the first and second measurement over the 4-month period (P>0.05). The ICC was 0.32 (95% confidence interval (CI)=0.13-0.49) for DHBA and 0.37 (95%CI=0.19-0.53) for DHPPA. These results suggest that AR metabolites cannot be considered to be better biomarkers of whole-grain wheat and rye intake than the intact AR in fasting plasma (ICC=0.42).

Accelerated Solvent Extraction of Alkylresorcinols in Food Products Containing Uncooked and Cooked Wheat

This research focuses on the overall extraction process of alkylresorcinols (ARs) from uncooked grains and baked products that have been processed with wheat, corn, rice, and white flour. Previously established extraction methods developed by Ross and colleagues, as well as a semiautomated method involving accelerated solvent extraction (ASE), were applied to extract ARs within freshly ground samples. For extraction of alkylresorcinols, nonpolar solvents such as ethyl acetate have been recommended for the extraction of uncooked foods, and polar solvents such as 1-propanol:water (3:1 v/v) have been recommended for the extraction of baked foods that contain rye, wheat, or other starch-rich grains. A comparison of AR extraction methods has been investigated with the application of gas chromatography and a flame ionization detector (GC-FID) to quantify the AR content. The goal of this research was to compare the rapid accelerated solvent extraction of the alkylresorcinols (ASE-AR) method to the previous manual AR extraction methods. Results for this study as well as the investigation of the overall efficiency of ASE-AR extraction with the use of a spiking study indicated that it can be comparable to current extraction methods but with less time required. Furthermore, the extraction time for ASE (approximately 40 min) is much more convenient and less tedious and time-consuming than previously established methods, which range from 5 h for processed foods to 24 h for raw grains.

Alkylresorcinol Metabolite Concentrations in Spot Urine Samples Correlated with Whole Grain and Cereal Fiber Intake but Showed Low to Modest Reproducibility over One to Three Years in U.S. Women1–3

AbstractTwo alkylresorcinol (AR) metabolites, 3, 5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA), in urine have been suggested as biomarkers of whole grain (WG) and cereal fiber intake but the long-term reproducibility and correlation with habitual intake has not been determined. Therefore, we evaluated the long-term reproducibility of AR metabolites in spot urine samples and investigated their correlation with habitual WG and cereal fiber intake in U.S. women. AR metabolites were analyzed in 104 women participating in the Nurses' Health Study II and WG and fiber intakes were assessed using a FFQ. Long-term reproducibility was assessed by calculating the intra-class correlation coefficients (ICC) using samples taken 1–3 y (mean 1.8 y) apart. The observed Spearman correlation coefficients (rs) and rs adjusted for within-participant variation in the biomarker were calculated between WG and fiber intake and biomarkers. The long-term reproducibility was poor for DHBA [ICC = 0.17 (95% CI: 0.05, 0.43)] and modest for DHPPA [ICC = 0.31 (95% CI: 0.17, 0.51)]. The correlation between WG intake in 1995 and DHPPA measured 2 y later was 0.37 (P < 0.0001); the adjusted correlation was 0.60 (95% CI: 0.37, 0.76). Cereal fiber and WG intake were similarly correlated to the biomarkers. DHPPA in spot urine samples reflected WG intake despite relatively low intake of food sources of AR. The poor to modest reproducibility may limit the use of single measurements of these biomarkers in cohort studies in the US, where WG intake is relatively low and has changed over time. But DHPPA in repeated samples may be useful for validating WG intake and assessing compliance in WG intervention studies.

Antimicrobial activity of the protozoan toxin climacostol and its derivatives

Climacostol is a defense toxin produced by the ciliated protozoan Climacostomum virens and belongs to resorcinolic lipids, a group of compounds that shows antimicrobial, antiparasitic, and cytotoxic activities. In this study we investigate the antimicrobial activity of climacostol and its alkyl and alkynyl derivatives against a panel of bacterial and fungal pathogens. Our results show a good and comparable antimicrobial activity of the three compounds, which have resulted effective against Gram-positive bacteria and Candida with MIC and MBC ranging from 8 to 32 mg L−1, whereas no significant effect against Gram-negative species has been observed. Taken as a whole, the experimental data reported in the current study suggest that differences in the saturation rate of the lateral chain of climacostol are not related to the activity of the molecule. Therefore, it is likely that the general structure of the two moieties, i.e., the di-hydroxy-phenyl group and the alkenyl chains, contributes to the overall antibiotic behaviour.