Absorption of plant lignans from cereals in an experimental pig model

Optimal extraction conditions and quantification of lignan phytoestrogens in cereal grains using targeted LC-MS/MS

Lignans are phytoestrogens found in various forms such as glycosides, ester-linked oligomers, and aglycones in a variety of foods, including soy products, legumes, grains, nuts, vegetables, and fruits. This study aimed to optimize the extraction of lignans from cereal grains using response surface methodology (RSM). Lignans, including secoisolariciresinol (Seco), matairesinol (Mat), pinoresinol (Pin), lariciresinol (Lar), and syringaresinol (Syr), were quantified using high-performance liquid chromatography-tandem mass spectrometry. A Box-Behnken design was employed to determine the optimal values for three extraction parameters: temperature (X1: 20°C-60°C), methanol concentration (X2: 60%-100%), and extraction time (X3: 30-90 min). The highest lignan contents were obtained at X1 = 44.24°C, X2 = 84.64%, and X3 = 53.63 min. To apply these experimental conditions to the actual experiment, the optimal conditions were slightly adjusted to X1 = 40°C, X2 = 80%, and X3 = 60 min. The predicted results closely matched the experimental results obtained using the modified optimal extraction conditions. The highest lignan content found in barley sprouts (85.930 μg/100 g), however, most grains exhibited relatively low concentrations of lignans. These findings provide valuable insights into the lignan content of grains and contribute to the generation of reliable data in this field.

Comparative Study on the Absorption and Metabolism of Pinoresinol and Pinoresinol-4-O-β-D-Glucopyranoside in Mice

SCOPE

Lignans are a group of phenolic compounds commonly found in plants, often in the form of glycosides. This study investigates the differences in the digestion, absorption, and metabolism of lignans and their glucosides using pinoresinol (PIN) and pinoresinol-4-O-β-D-glucopyranoside (PMG).

METHODS AND RESULTS

After oral administration mice PIN and PMG with a dose of 0.1 µmol kg-1 . The results showed that the stomach and small intestine rapidly absorbe PIN and PMG in their prototype form. After oral administration of 0.25 h, serum levels of PIN and PMG reach peak values of 61.14 and 52.97 ng mL-1 , respectively. This indicates a faster PIN absorption rate than PMG, likely due to the glycosides attach to the parent compound, with concentrations of 1574.14 and 876.75 ng g-1 , respectively. Pharmacokinetic analysis reveals that PIN has a greater area under the curve and a longer half-life than PMG in serum and liver. Moreover, mice in the PIN group exhibit higher metabolite levels in the serum and liver compared to those in the PMG group.

CONCLUSION

The deglycosylation process that occurs during the pickling of white radish facilitates the absorption and metabolism of the lignans fraction in the body.

The What and Who of Dietary Lignans in Human Health: Special Attention to Estrogen Effects and Safety Evaluation

Lignans are a group of phenolic compounds found in plant-based diets. The human body can obtain lignans through diet, which are then metabolized into enterolignans. The enterolignans have been linked to several health benefits, including anticancer, anti-inflammatory, antioxidant effects, and estrogen effects. This review explores the relationship between the estrogenic effects of lignans and health. This review not only considers the estrogen-like activity of lignans but also discusses the safe dosage of lignans at different life stages. In addition, this review also identified other types of bioactive compounds that can act synergistically with lignans to promote health. Studies have shown that lignan administration during pregnancy and lactation reduces the risk of breast cancer in offspring. Further studies are needed to investigate the estrogenic safety effects of lignan on pregnant women and children. Whether lignans combine with other nutrients in complex food substrates to produce synergistic effects remains to be investigated. This review provides a basis for future studies on the safe dose of lignan and recommended dietary intake of lignan. We believe that the acquired as discussed here has implications for developing dietary therapies that can promote host nutrition and modulate estrogenic diseases.

Interplay between Lignans and Gut Microbiota: Nutritional, Functional and Methodological Aspects

Lignans are non-flavonoid polyphenols present in a wide range of foods frequently consumed in the Western world, such as seeds, vegetables and fruits, and beverages such as coffee, tea and wine. In particular, the human gut microbiota (GM) can convert dietary lignans into biologically active compounds, especially enterolignans (i.e., enterolactone and enterodiol), which play anti-inflammatory and anti-oxidant roles, act as estrogen receptor activators and modulate gene expression and/or enzyme activity. Interestingly, recent evidence documenting those dietary interventions involving foods enriched in lignans have shown beneficial and protective effects on various human pathologies, including colorectal and breast cancer and cardiovascular diseases. However, considering that more factors (e.g., diet, food transit time and intestinal redox state) can modulate the lignans bioactivation by GM, there are usually remarkable inter-individual differences in urine, fecal and blood concentrations of enterolignans; hence, precise and validated analytical methods, especially gas/liquid chromatography coupled to mass spectrometry, are needed for their accurate quantification. Therefore, this review aims to summarize the beneficial roles of enterolignans, their interaction with GM and the new methodological approaches developed for their evaluation in different biological samples, since they could be considered future promising nutraceuticals for the prevention of human chronic disorders.

Rye Flour and Rye Bran: New Perspectives for Use

Rye (Secale cereale L.) is abundantly cultivated in countries like Europe and North America, particularly in regions where soil and climate conditions are unfavorable for the growth of other cereals. Among all the cereals generally consumed by human beings, rye grains are characterized by the presence of the highest content of fiber. They are also a rich source of many phytochemical compounds, which are mainly distributed in the outer parts of the grain. This review focuses on the current knowledge regarding the characteristics of rye bran and wholemeal rye flour, as well as their applications in the production of both food and nonfood products. Previous studies have shown that the physicochemical properties of ground rye products are determined by the type of milling technique used to grind the grains. In addition, the essential biologically active compounds found in rye grains were isolated and characterized. Subsequently, the possibility of incorporating wholemeal rye flour, rye bran, and other compounds extracted from rye bran into different industrial products is discussed.

The role of rye bran and antibiotics on the digestion, fermentation process and short-chain fatty acid production and absorption in an intact pig model

The effects of arabinoxylan (AX)-rich rye bran based diet (RB) and antibiotics on digestion, fermentation and short-chain fatty acids (SCFA) absorption were studied compared with an iso-dietary fibre (DF) cellulose based diet (CEL). Thirty female pigs (body weight 72.5 ± 3.9 kg) were fed a standard swine diet in week 1, CEL as wash-out for bran-associated bioactive components in week 2 and then divided into 3 groups fed either the CEL (n = 10) or RB (n = 20) for 2 weeks, where 10 pigs from RB had daily intramuscular antibiotic injections (RB+) and the other 10 pigs were untreated (RB-) in week 4. In RB, the degradation of AX mainly occurred in caecum and proximal colon (P < 0.01) and to a higher extent than cellulose, which on the other hand, irrespective of antibiotic treatment, was less degraded in the RB groups than in the CEL (P < 0.01). The apparent digestibility of fat and protein in the distal small intestine was lower for RB than CEL (P < 0.05), the protein digestibility remained lower in most of the colon, and the digestibility was not affected by treatment with antibiotics. The colonic concentrations of SCFA, acetate and propionate as well as the butyrate concentration in the distal colon were lower with the RB treatments compared with CEL (P < 0.01). Caecal butyrate concentrations were on the other hand higher, and a significant reduction was seen with antibiotic treatment (P < 0.001). The daily net absorption of SCFA and acetate was lower with RB than with CEL (P < 0.01). In conclusion, RB resulted in different DF degradation processes and SCFA production compared with CEL, whereas antibiotic treatment had marginal effects on the intestinal DF degradation but hampered butyrate production.

Lignans and Gut Microbiota: An Interplay Revealing Potential Health Implications

Plant polyphenols are a broad group of bioactive compounds characterized by different chemical and structural properties, low bioavailability, and several in vitro biological activities. Among these compounds, lignans (a non-flavonoid polyphenolic class found in plant foods for human nutrition) have been recently studied as potential modulators of the gut-brain axis. In particular, gut bacterial metabolism is able to convert dietary lignans into therapeutically relevant polyphenols (i.e., enterolignans), such as enterolactone and enterodiol. Enterolignans are characterized by various biologic activities, including tissue-specific estrogen receptor activation, together with anti-inflammatory and apoptotic effects. However, variation in enterolignans production by the gut microbiota is strictly related to both bioaccessibility and bioavailability of lignans through the entire gastrointestinal tract. Therefore, in this review, we summarized the most important dietary source of lignans, exploring the interesting interplay between gut metabolites, gut microbiota, and the so-called gut-brain axis.

The Strength of the Nutrient Solution Modulates the Functional Profile of Hydroponically Grown Lettuce in a Genotype-Dependent Manner

Considering that functional components of plant foods are mainly secondary-metabolism products, we investigated the shaping of health-promoting compounds in hydroponically grown butterhead lettuce (Lactuca sativa L. var. capitata) as a function of the strength of the nutrient solution utilized. To this aim, untargeted metabolomics profiling, in vitro antioxidant capacity (total phenolics, 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), cupric reducing antioxidant capacity (CUPRAC), and ferric reducing antioxidant power (FRAP) assays), and the inhibition of selected enzyme activities were investigated in two butterhead lettuce cultivars with different pigmentation, i.e., green and red Salanova. Full-strength nutrition, together with half- and quarter-strength solutions of macronutrients, was tested. Our results indicate that by reducing the nutrients strength, we could elicit a distinctive shaping of the phenolic profile of lettuce. It is noteworthy that only specific classes of phenolics (namely, lignans and phenolic acids, followed by flavones and anthocyanins) were modulated by the induction of nutritional eustress (fold-change values in the range between -5 and +11). This indicates that specific responses, rather than a generalized induction of phenolic compounds, could be observed. Nonetheless, a genotype-dependent response could be observed, with the red cultivar being much more responsive to nutritional deprivation than the green Salanova lettuce. Indeed, analysis of variance (ANOVA) confirmed a genotype x nutrition interaction in red Salanova (p < 0.001). As a consequence of the changes in phenolic composition, also the antioxidant capacity (p < 0.001) and amylase inhibition (p < 0.001) properties were affected by the growing conditions. However, the effect on cholinesterase and tyrosinase inhibition was poorly affected by the nutritional strength. Provided that yields are not compromised, the application of a controlled nutritional eustress in hydroponically cultivated lettuce may represent a valuable strategy to produce food with tailored functional features in a sustainable manner.

Genetic basis for the cooperative bioactivation of plant lignans by Eggerthella lenta and other human gut bacteria

Plant-derived lignans, consumed daily by most individuals, are thought to protect against cancer and other diseases¹; however, their bioactivity requires gut bacterial conversion to enterolignans². Here, we dissect a four-species bacterial consortium sufficient for all five reactions in this pathway. A single enzyme (benzyl ether reductase; ber), was sufficient for the first two biotransformations, variable between strains of Eggerthella lenta, critical for enterolignan production in gnotobiotic mice, and unique to Coriobacteriia. Transcriptional profiling (RNAseq) independently identified ber and genomic loci upregulated by each of the remaining substrates. Despite their low abundance in gut microbiomes and restricted phylogenetic range, all of the identified genes were detectable in the distal gut microbiomes of most individuals living in Northern California. Together, these results emphasize the importance of considering strain-level variations and bacterial co-occurrence to gain a mechanistic understanding of the bioactivation of plant secondary metabolites by the human gut microbiome.

Naturally Lignan-Rich Foods: A Dietary Tool for Health Promotion?

Dietary guidelines universally advise adherence to plant-based diets. Plant-based foods confer considerable health benefits, partly attributable to their abundant micronutrient (e.g., polyphenol) content. Interest in polyphenols is largely focused on the contribution of their antioxidant activity to the prevention of various disorders, including cardiovascular disease and cancer. Polyphenols are classified into groups, such as stilbenes, flavonoids, phenolic acids, lignans and others. Lignans, which possess a steroid-like chemical structure and are defined as phytoestrogens, are of particular interest to researchers. Traditionally, health benefits attributed to lignans have included a lowered risk of heart disease, menopausal symptoms, osteoporosis and breast cancer. However, the intake of naturally lignan-rich foods varies with the type of diet. Consequently, based on the latest humans' findings and gathered information on lignan-rich foods collected from Phenol Explorer database this review focuses on the potential health benefits attributable to the consumption of different diets containing naturally lignan-rich foods. Current evidence highlight the bioactive properties of lignans as human health-promoting molecules. Thus, dietary intake of lignan-rich foods could be a useful way to bolster the prevention of chronic illness, such as certain types of cancers and cardiovascular disease.

Advances in extraction and analysis of phenolic compounds from plant materials

Phenolic compounds, the most abundant secondary metabolites in plants, have received more and more attention in recent years because of their distinct bioactivities. This review summarizes different types of phenolic compounds and their extraction and analytical methods used in the recent reports, involving 59 phenolic compounds from 52 kinds of plants. The extraction methods include solid-liquid extraction, ultrasound-assisted extractions, microwave-assisted extractions, supercritical fluid extraction, and other methods. The analysis methods include spectrophotometry, gas chromatography, liquid chromatography, thin-layer chromatography, capillary electrophoresis, and near-infrared spectroscopy. After illustrating the specific conditions of the analytical methods, the advantages and disadvantages of each method are also summarized, pointing out their respective suitability. This review provides valuable reference for identification and/or quantification of phenolic compounds from natural products.

Rye Bran Modified with Cell Wall-Degrading Enzymes Influences the Kinetics of Plant Lignans but Not of Enterolignans in Multicatheterized Pigs

Background: Whole-grain intake is associated with a lower risk of chronic Western-style diseases, possibly brought about by the high concentration of phytochemicals, among them plant lignans (PLs), in the grains.Objective: We studied whether treatment of rye bran with cell wall-degrading enzymes changed the solubility and kinetics of PLs in multicatheterized pigs.Methods: Ten female Duroc × Danish Landrace × Yorkshire pigs (60.3 ± 2.3 kg at surgery) fitted with permanent catheters were included in an incomplete crossover study. The pigs were fed 2 experimental diets for 1-7 d. The diets were rich in PLs and based on nontreated lignan-rich [LR; lignan concentration: 20.2 mg dry matter (DM)/kg] or enzymatically treated lignan-rich (ENZLR; lignan concentration: 27.8 mg DM/kg) rye bran. Plasma concentrations of PLs and enterolignans were quantified with the use of targeted LC-tandem mass spectrometry. Data were log transformed and analyzed with mixed-effects, 1-compartment, and asymptotic regression models.Results: The availability of PLs was 38% greater in ENZLR than in LR, and the soluble fraction of PLs was 49% in ENZLR compared with 35% in LR diets. PLs appeared in the circulation 30 min after intake of both the ENZLR and LR diets. Postprandially, consumption of ENZLR resulted in a 4-times-greater (P < 0.0001) plasma PL concentration compared with LR. The area under the curve (AUC) measured 0-360 min after ENZLR intake was ∼2 times higher than after LR intake. A 1-compartment model could describe the postprandial increase in plasma concentration after ENZLR intake, whereas an asymptotic regression model described the plasma concentrations after LR intake. Despite increased available and soluble PLs, ENZLR did not increase plasma enterolignans.Conclusion: The modification of rye bran with cell wall-degrading enzymes resulted in significantly greater plasma concentrations of PLs and the 4-h AUC, particularly syringaresinol, in multicatheterized pigs.

Phenylpropanoid profiling reveals a class of hydroxycinnamoyl glucaric acid conjugates in Isatis tinctoria leaves

The brassicaceous herb, Isatis tinctoria, is an ancient medicinal plant whose rosette leaf extracts have anti-inflammatory and anti-allergic activity. Brassicaceae are known to accumulate a variety of phenylpropanoids in their rosette leaves acting as antioxidants and a UV-B shield, and these compounds often have pharmacological potential. Nevertheless, knowledge about the phenylpropanoid content of I. tinctoria leaves remains limited to the characterization of a number of flavonoids. In this research, we profiled the methanol extracts of I. tinctoria fresh leaf extracts by liquid chromatography - mass spectrometry (LC-MS) and focused on the phenylpropanoid derivatives. We report the structural characterization of 99 compounds including 18 flavonoids, 21 mono- or oligolignols, 2 benzenoids, and a wide spectrum of 58 hydroxycinnamic acid esters. Besides the sinapate esters of malate, glucose and gentiobiose, which are typical of brassicaceous plants, these conjugates comprised a large variety of glucaric acid esters that have not previously been reported in plants. Feeding with ¹³C₆-glucaric acid showed that glucaric acid is an acyl acceptor of an as yet unknown acyltransferase activity in I. tinctoria rosette leaves. The large amount of hydroxycinnamic acid derivatives changes radically our view of the woad metabolite profile and potentially contributes to the pharmacological activity of I. tinctoria leaf extracts.

Effect of Antibiotics and Diet on Enterolactone Concentration and Metabolome Studied by Targeted and Nontargeted LC-MS Metabolomics

High plant lignan intake is associated with a number of health benefits, possibly induced by the lignan metabolite enterolactone (ENL). The gut microbiota plays a crucial role in converting dietary lignans into ENL, and epidemiological studies have shown that use of antibiotics is associated with lower levels of ENL. Here we investigate the link between antibiotic use and lignan metabolism in pigs using LC-MS/MS. The effect of lignan intake and antibiotic use on the gut microbial community and the pig metabolome is studied by 16S rRNA sequencing and nontargeted LC-MS. Treatment with antibiotics resulted in substantially lower concentrations of ENL compared with concentrations detected in untreated animals, whereas the plasma concentrations of plant lignans were unchanged. Both diet and antibiotic treatment affected the clustering of urinary metabolites and significantly altered the proportions of taxa in the gut microbiota. Diet, but not antibiotic treatment, affected the plasma lipid profile, and a lower concentration of LDL cholesterol was observed in the pigs fed a high lignan diet. This study provides solid support for the associations between ENL concentrations and use of antibiotics found in humans and indicates that the lower ENL concentration may be a consequence of the ecological changes in the microbiota.

Validated LC-MS/MS Method for the Quantification of Free and Bound Lignans in Cereal-Based Diets and Feces

Despite the extensive literature describing the biological effects of phenolic compounds from cereals, little is known about their bioaccessibility in the food matrix. This paper describes a validated LC-MS/MS method for the quantification of free and total content (free + bound) of eight plant lignans (matairesinol, hydroxymatairesinol, secoisolariciresinol, lariciresinol, isolariciresinol, syringaresinol, medioresinol, and pinoresinol) and two enterolignans (enterodiol and enterolactone) in cereal-based diets/bread and feces. The method consisted of alkaline methanolic extraction combined with enzymatic hydrolyses, for the measurement of the total concentration of lignans, and methanolic extraction combined with enzymatic hydrolysis, for the measurement of free lignans, followed by solid phase extraction (SPE). The strength of this LC-MS/MS method is that it can be combined with different types of samples, because the SPE and LC-MS/MS platforms are similar to our previously published method for plasma and urine.