[Lignans of Trachelospermum asiaticum var. intermedium. VI. Dehydration of methyltrachelogenin and its application to the related lignans].
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Chemical Phenomena↗
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Intestinal metabolism of rye lignans in pigs.
To study the intestinal metabolism of lignans, the concentrations of plant and mammalian lignans in intestinal digesta sampled along the intestinal tract of pigs were determined by isotope dilution GC-MS. The pigs were fed rye-bread diets made from either whole rye-grains or rye-grain milling fractions enriched in pericarp-testa, aleurone or endosperm cells. The content and characteristics of dietary fibre varied between diets and had been shown to induce different colon fermentation patterns. As the metabolism of lignans depends on the action of the intestinal flora, we tested whether the rye-bread diets influence the metabolism of lignans. In the ileum, the lignans were mainly present as conjugated plant lignans, which were determined only when the analytical procedure included a hydrolysis step. High recovery of dietary lignans in the ileum may indicate that the lignans enter the enterohepatic circulation. In addition, two to three times the intake of lignans were recovered in the faeces when the diets had a high content of dietary fibre suggesting underestimation of plant lignans in the diet. Most of the plant lignans disappeared from the intestinal tract between the terminal ileum and the caecum. The intestinal concentrations and the disappearance of lignans correlated with the content of lignans in the diet, being highest on the pericarp-testa diet and lowest on the endosperm diet. No effect of fermentation pattern on the intestinal metabolism of lignans was observed. The lignans were liberated from the pericarp-testa diet although the plant cell walls remained largely undegraded.
Analysis of Variance↗
Lignans in homemade and commercial products containing flaxseed.
Epidemiologic, in vitro, and in vivo studies support the hypothesis that mammalian lignans have cancer protective effects. Flaxseed is the richest source of plant precursors to mammalian lignans. However, there are limited data on the lignans from processed foods containing flaxseed, despite increasing flaxseed use. Thus the objective of this study was to quantify the lignans in flaxseed-containing processed foods and their relationship to the percent flaxseed in the food. Twenty-five foods including raw flaxseed, homemade products containing flaxseed, and commercial breads and breakfast cereals with and without flaxseed were subjected to an in vitro fermentation designed to simulate the colonic environment necessary for the conversion of plant precursors to mammalian lignans. The lignan production from cereals containing flaxseed was significantly greater than that from their component grains (p < or = 0.01), and the lignan production from breads containing > 4% flaxseed was significantly greater than that from breads containing < 4% flaxseed (p < or = 0.05). Lignan production was significantly related to percent flaxseed in homemade products (r = 0.95, p < or = 0.01) and breakfast cereals (r = 0.997, p < or = 0.0001). Although a significant relationship was also observed in commercial breads (r = 0.58, p < or = 0.05), the correlation was lower because of the variability in different flaxseed varieties and the lignan contribution from other grains and oilseeds in these products. In conclusion, the addition of flaxseed to processed foods increased the production of mammalian lignans significantly. The amount of lignan production was linearly dependent on the percent flaxseed but was also influenced by other grains and the variety of flaxseed.
Bread↗
Intake of the plant lignans secoisolariciresinol, matairesinol, lariciresinol, and pinoresinol in Dutch men and women.
Enterolignans (enterolactone and enterodiol) are phytoestrogens that are formed by the colonic microflora from plant lignans. They may reduce the risk of certain types of cancer and cardiovascular diseases. Initially, only secoisolariciresinol and matairesinol were considered to be enterolignan precursors, but recently, new precursors such as lariciresinol and pinoresinol were identified. We recently developed a lignan database including 4 major enterolignan precursors. We used this database to estimate lignan intake in a representative sample of Dutch men and women participating in the Dutch Food Consumption Survey, carried out in 1997-1998. Median total lignan intake among 4660 adults (19-97 y old) was 979 microg/d. Total lignan intake did not differ between men and women; thus, the lignan density of the diet was significantly higher (P < 0.001) in women than in men. Lignan intake was strongly skewed toward higher values (range 43-77584 microg/d, mean 1241 microg/d). Lariciresinol and pinoresinol contributed 75% to lignan intake, whereas secoisolariciresinol and matairesinol contributed only 25%. The major food sources of lignans were beverages (37%), vegetables (24%), nuts and seeds (14%), bread (9%), and fruits (7%). Lignan intake was significantly (P < 0.001) correlated with intake of dietary fiber (r = 0.46), folate (r = 0.39), and vitamin C (r = 0.44). Older persons, nonsmokers, vegetarians, and persons with a low BMI or a high socioeconomic status had higher lignan intakes than their counterparts. In brief, this study shows that the amount of enterolignan precursors in the diet has previously been largely underestimated.
Adult↗
Hypocholesterolemic and antiatherosclerotic effect of flax lignan complex isolated from flaxseed.
Hypercholesterolemia, low HDL-C and oxygen radicals have been implicated in the development of atherosclerosis. Lignan complex isolated from flaxseed contains secoisolariciresinol diglucoside (SDG), 3-hydroxy-3methylglutaric acid (HMGA) and cinnamic acids. SDG and cinnamic acids are antioxidants, and HMGA is a hypocholesterolemic agent. Antioxidants are known to reduce hypercholesterolemic atherosclerosis. The objectives of this study were to determine if lignan complex reduces (i) serum cholesterol, (ii) oxidative stress, and (iii) atherosclerosis in hypercholesterolemic rabbits. Rabbits were assigned to four groups: Group I, control; Group II, lignan complex control (lignan complex, 40 mg/kg body weight daily orally); Group III, 0.5% cholesterol; Group IV, 0.5% cholesterol diet+lignan complex, (40 mg/kg body weight daily orally). Blood samples were collected before (time 0) and after 1 and 2 months of experimental diets for measurement of serum triglycerides (TG), total cholesterol (TC), LDL-C, HDL-C and serum malondialdehyde (MDA), a lipid peroxidation product. At the end of the protocol, the aorta was removed for measurement of atherosclerotic plaques, MDA and aortic tissue chemiluminescence (Aortic CL), a marker of antioxidant reserve. Rabbits in Group III developed atherosclerosis (50.84+/-6.23% of the intimal surface of the aorta was covered with atherosclerotic changes) which was associated with an increase in the serum TG, TC, LDL-C, HDL-C, MDA and aortic MDA and antioxidant reserve. Lignan complex reduced the development of atherosclerosis by 34.37% and this was associated with a decrease in serum TC by 20%, LDL-C by 14%, TC/HDL-C by 34%, serum MDA by 35% and aortic MDA by 58%. Serum HDL-C was elevated by 30% in hypercholesterolemic rabbits and by 25% in normocholesterolemic rabbits with lignan complex. Lignan complex did not affect the TC and LDL-C and serum MDA in the normocholesterolemic rabbits. However, it increased the aortic MDA in the normocholesterolemic rabbits. These results suggest that lignan complex isolated from flaxseed reduced the extent of hypercholesterolemic atherosclerosis and this effect was associated with marked decreases in oxidative stress, serum total cholesterol, LDL-C and risk ratio, and elevation of serum HDL-C. Lignan complex may, therefore, be beneficial in preventing atherosclerosis, and reducing risk factors for coronary artery disease and stroke.
Animals↗
Chromatographic analysis of lignans.
Methods and procedures for analysis of lignans in trees and other plants are reviewed. The importance of cautious sample handling and pretreatment procedures to avoid contamination, loss of sample, and unwanted chemical reactions is discussed. Sequential extraction with a non-polar solvent followed by extraction with acetone or ethanol is recommended to separate the lignans from the plant matrix. An additional step of acid, alkaline, or enzymatic hydrolysis may be necessary for some plant matrixes. Flash chromatography is a convenient method for preparative separation and isolation of pure lignans from raw extracts. TLC is very suitable for qualitative screening of extracts and for monitoring of lignan isolation and purification steps. Trimethylsilyl ethers of lignans can be separated and quantified by GC even in the case of complex mixtures of lignans and other polyphenols, and the lignans can be identified by GC-MS in a routine manner. HPLC on reversed-phase columns is especially suited for analysis of lignans and their metabolites in biological matrixes. The recent development of HPLC-electrospray ionisation (ESI)-iontrap MS (MS(n)) and corresponding techniques with high sensitivity and selectivity has proven valuable in lignan analysis. Lignan enantiomers can be separated on chiral HPLC columns.
Animals↗
Liquid chromatography method for plant and mammalian lignans in human urine.
Recently new mammalian lignan precursors were identified but no analysis methods are available for assay of those compounds in human urine. Previously published methods were developed for GC-MS about only two plant lignans were included. Consequently, a method for HPLC equipped with a coulometric electrode array detector was developed to measure plant and mammalian lignans in human urine. The plant lignans, secoisolariciresinol (Seco), matairesinol (Mat), lariciresinol (Lar), pinoresinol (Pin), syringaresinol (Syr) and isolariciresinol (IsoL) were included into the new method together with two mammalian lignans, enterolactone (Enl) and enterodiol (End). Validation of the method demonstrated that it could be applied to normal urine containing low amounts of plant lignans and moderate amounts of mammalian lignans, but the method was also applicable for samples from study subjects in supplementation studies, i.e. sample with very high concentrations of mammalian lignans. The method was found to be a useful tool for studies on plant lignan intake and the activity of micro flora in the metabolism of plant lignans.
Animals↗
Sesamin is one of the major precursors of mammalian lignans in sesame seed (Sesamum indicum) as observed in vitro and in rats.
Plant lignans occur in many foods, with flaxseed presently recognized as the richest source. Some plant lignans can be converted by intestinal microbiota to the mammalian lignans, enterodiol and enterolactone, which may have protective effects against hormone-related diseases such as breast cancer. This study determined whether plant lignans in sesame seed, particularly sesamin, could be metabolized to the mammalian lignans. The total plant lignan concentration in sesame seed (2180 micromol/100 g) was higher than that in flaxseed (820 micromol/100 g). In vitro fermentation with human fecal inoculum showed conversion of sesamin to the mammalian lignans, although at a lower rate (1.1%) compared with that of secoisolariciresinol diglucoside (57.2%). However, when fed to female Sprague-Dawley rats for 10 d, sesamin (15 mg/kg body weight) and a 10% sesame seed diet resulted in greater (P < 0.05) urinary mammalian lignan excretion (3.2 and 11.2 micromol/d, respectively), than the control (< 0.05 micromol/d). We conclude that sesame seed is a rich source of mammalian lignan precursors and sesamin is one of them. From intermediate metabolites of sesamin identified in rat urine by GC-MS, a tentative metabolic pathway of sesamin to mammalian lignans is suggested.
Animals↗
Lignan contents of Dutch plant foods: a database including lariciresinol, pinoresinol, secoisolariciresinol and matairesinol.
Enterolignans (enterodiol and enterolactone) can potentially reduce the risk of certain cancers and cardiovascular diseases. Enterolignans are formed by the intestinal microflora after the consumption of plant lignans. Until recently, only secoisolariciresinol and matairesinol were considered enterolignan precursors, but now several new precursors have been identified, of which lariciresinol and pinoresinol have a high degree of conversion. Quantitative data on the contents in foods of these new enterolignan precursors are not available. Thus, the aim of this study was to compile a lignan database including all four major enterolignan precursors. Liquid chromatography-tandem mass spectrometry was used to quantify lariciresinol, pinoresinol, secoisolariciresinol and matairesinol in eighty-three solid foods and twenty-six beverages commonly consumed in The Netherlands. The richest source of lignans was flaxseed (301,129 microg/100 g), which contained mainly secoisolariciresinol. Also, lignan concentrations in sesame seeds (29,331 microg/100 g, mainly pinoresinol and lariciresinol) were relatively high. For grain products, which are known to be important sources of lignan, lignan concentrations ranged from 7 to 764 microg/100 g. However, many vegetables and fruits had similar concentrations, because of the contribution of lariciresinol and pinoresinol. Brassica vegetables contained unexpectedly high levels of lignans (185-2321 microg/100 g), mainly pinoresinol and lariciresinol. Lignan levels in beverages varied from 0 (cola) to 91 microg/100 ml (red wine). Only four of the 109 foods did not contain a measurable amount of lignans, and in most cases the amount of lariciresinol and pinoresinol was larger than that of secoisolariciresinol and matairesinol. Thus, available databases largely underestimate the amount of enterolignan precursors in foods.
Beverages↗
Mammalian lignan production from various foods.
Mammalian lignans such as enterolactone and enterodiol, which are produced in the colon from precursors in foods, have been suggested as playing a role in the cancer-protective effect of vegetarian diets. Despite this, very little is known regarding the amount that is produced from different food products. Therefore, the objective of this study was to determine the production of mammalian lignans from 68 common plant foods by using the technique of in vitro fermentation with human fecal microbiota, which simulates colonic fermentation. Results showed a wide range (21-67,541 microgram(s)/100 g sample) in the amount of lignans produced. On the average as a group, the oilseeds produced the highest amounts (20,461 +/- 12,685), followed by the dried seaweeds (900 +/- 247), whole legumes (562 +/- 211), cereal brans (486 +/- 90), legume hulls (371 +/- 52), whole grain cereals (359 +/- 81), vegetables (144 +/- 23), and fruits (84 +/- 22). The vegetables produced the second highest concentration of lignans (1,546 +/- 280) when the data were expressed on a moisture-free basis. Flaxseed flour and its defatted meal were the highest producers of lignans (mean 60,110 +/- 7,431). Lignan production with the in vitro method related well to the urinary lignan excretion observed in rats and humans. The data should be useful in the estimation of lignan production from a given diet and in the formulation of high-lignan-producing diet for the purpose of reducing the cancer risk.
4-Butyrolactone↗
Human metabolism of mammalian lignan precursors in raw and processed flaxseed.
BACKGROUND: The mammalian lignans enterolactone and enterodiol are produced in the colon by the action of bacteria on the plant precursor secoisolariciresinol diglycoside, which is found in high concentrations in flaxseed. OBJECTIVE: Two experiments were conducted to determine 1) whether there is a dose response in urinary lignan excretion with increasing flaxseed intake, 2) whether flaxseed processing affects lignan excretion, 3) peak plasma lignan concentrations, and 4) plasma lignan concentrations after chronic supplementation. DESIGN: Nine healthy young women supplemented their diets with 5, 15, or 25 g raw or 25 g processed (muffin or bread) flaxseed for 7 d during the follicular phase of their menstrual cycles. Twenty-four-hour urine samples were collected at baseline and on the final day of supplementation. As an adjunct to the 25-g-flaxseed arm, subjects consumed the supplement for an additional day and blood and urine samples were collected at specific intervals. All blood and urine samples were analyzed for enterolactone and enterodiol by gas chromatography-mass spectroscopy. RESULTS: A dose-dependent urinary lignan response to raw flaxseed was observed (r = 0.72, P < 0.001). The processing of flaxseed as a muffin or bread did not affect the quantity of lignan excretion. Plasma lignan concentrations were greater (P < or = 0.05) than baseline by 9 h after flaxseed ingestion (29.35+/-3.69 and 51.75+/-7.49 nmol/L, respectively). The total plasma area under the curve was higher on the eighth than on the first day (1840.15+/-343.02 and 1027.15+/-95.71 nmol x h/L, respectively). CONCLUSION: Mammalian lignan production from flaxseed precursors is dependent on time and dose but not on processing.
4-Butyrolactone↗
Intake of lignans is associated with serum enterolactone concentration in Finnish men and women.
The mammalian lignans (a form of phytoestrogens), metabolically derived by the intestinal microflora from dietary precursors, may have several health benefits. Information concerning their dietary sources and bioavailability is scarce. We assessed lignan intake via a 24-h dietary recall (n = 2852) and determined serum enterolactone (EL) concentration (n = 1784) in 25- to 64-y-old Finnish men and women participating in a national survey in 1997. Mean intake of lignans [sum of matairesinol (MAT) and secoisolariciresinol (SECO)] in men and women was 173 microg/d (19 microg/MJ) and 151 microg/d (23 microg/MJ), respectively. SECO made up over two thirds of the total lignan intake. The major sources of SECO were fruit, berries and cereals, whereas MAT derived almost exclusively from cereals. Lignan intake was positively associated with serum EL concentration (r = 0.19, P < 0.0001), i.e., the mean EL concentration in the highest quintile of lignan intake was 50% higher than that in the lowest quintile. We conclude that lignans are common components of the Finnish diet, although the mean daily intake is low (<0.2 mg). The main dietary sources of lignans, i.e., whole grain, vegetables and fruits, are foods commonly associated with lower risk of cardiovascular diseases and cancer. Serum EL concentration is a feasible biomarker of lignan intake.
4-Butyrolactone↗
Flax lignans--analytical methods and how they influence our lunderstanding of biological activity.
Flaxseed (Linum usitatissimum L.) is a major source of dietary intake of lignans by virtue of the high concentrations (0.7-1.5%) that are present in the seed. The principal lignan present in flaxseed is secoisolariciresinol diglucoside (SDG), which occurs as a component of a linear ester-linked complex in which the C6-OH of the glucose of SDG is esterified to the carboxylic acid of hydroxymethylglutaric acid. Also present in flaxseed and in resulting lignan extracts are significant quantities of 2 cinnamic acid glycosides. Our emerging understanding of the biological activity of flax lignans is based on studies using a variety of materials ranging from whole ground seed to pure SDG. The underlying assumption of most of these studies is that the biological activity of flax lignans results from their conversion to the mammalian lignans enterolactone (EL) and enterodiol (ED). There are, however, several intermediate compounds generated during the digestion and metabolism of flax lignans, including SDG and its aglycones and secoisolariciresinol (Seco), that are good candidates to be the principal bioactive molecule. This review will document the history of the development of lignan analytical methods and illustrate how analytical methods have influenced the interpretation of animal and human trials and our understanding of the biological activity of flax lignans.
4-Butyrolactone↗
Detection and identification of the plant lignans lariciresinol, isolariciresinol and secoisolariciresinol in human urine.
The mammalian lignans enterolactone and enterodiol are regular constituents of human urine and are excreted daily in mumol amounts. They are produced by metabolic action of intestinal bacteria from natural plant lignan precursors which are constituents of various food plants. However, natural plant lignans seem to occur very seldom in detectable amounts in human urine. The present investigation shows that only in 5% of the 150 diphenolic fractions extracted from the urine of women plant lignans other than the previously identified matairesinol could be found. The lignans lariciresinol, isolariciresinol and secoisolariciresinol were identified for the first time by comparison of their GC characteristics and mass spectra with the corresponding results of authentic synthesized reference compounds. Secoisolariciresinol is one natural precursor of the mammalian lignan enterodiol. Of the two other plant lignans, no animal or human metabolic products are known. The occurrence of chemically unchanged plant lignans in some cases in human urine could be a result of an insufficient metabolic capacity of intestinal bacteria, resulting in a decreased detoxification of phenolic plant products.
Adult↗
Structural determinants of plant lignans for growth of mammary tumors and hormonal responses in vivo.
Low risk of breast cancer (BC) has been proposed to be associated with high intake of lignans. Some plant lignans are converted to mammalian lignans, e.g., enterolactone (ENL), suggested to be the biologically active lignan forms. Until now, little attention has been paid to the possible biological activities of plant lignans, even though some plant lignans are absorbed and present in serum and urine. In this study, we have investigated the antitumorigenic and endocrine-modulatory activities of different plant lignans in order to clarify the structure-activity relationships. 7-Hydroxymatairesinol (HMR) is [corrected] converted to ENL, and both HMR and ENL inhibit the growth of 7,12-dimethylbenz[a]-anthracene (DMBA)-induced mammary cancer. Nortrachelogenin (NTG) resembles HMR, but has a hydroxyl group at C-8 instead of C-7 and is not converted to ENL. In DMBA-model, NTG showed no inhibition of tumor growth, but increased the uterine weight. Furthermore, life-long exposure to NTG increased uterine weight in immature females and ventral prostate weight in adult males. In contrast, life-long exposure to HMR had no effects on uterine or prostate weights at any age. Our results indicate that a difference in the position of one hydroxyl group results in distinct biological responses in vivo, as well as different lignan metabolite profiles.
4-Butyrolactone↗
Identification and stereochemical characterization of lignans in flaxseed and pumpkin seeds.
Phytoestrogens of the lignan type are widely distributed in plant-derived food items and are believed to protect against hormone-dependent cancer. The richest known dietary source of lignans is flaxseed. Flaxseed has been reported to contain glycosides of secoisolariciresinol as the major lignan, together with small amounts of matairesinol, isolariciresinol, and pinoresinol. Secoisolariciresinol, but none of the other lignans, has so far been identified in pumpkin seeds. In the present study, two different methods for the hydrolysis of lignan glycosides are compared. Artifact formation and loss of lignans under acidic conditions were observed. Lariciresinol was identified by GC-MS analysis in two different types of flaxseed (Linum usitatissimum L. and Linum flavum L.) and in pumpkin seeds (Cucurbita pepo L.) for the first time. Likewise, the novel lignan demethoxy-secoisolariciresinol was tentatively identified in the flaxseed samples. Stereochemical analysis by chiral HPLC of several lignans isolated from flaxseed showed that secoisolariciresinol, matairesinol, and lariciresinol consisted predominantly of one enantiomer.
Butylene Glycols↗
Species differences in the physiological activity of dietary lignan (sesamin and episesamin) in affecting hepatic fatty acid metabolism.
The effect of sesame (Sesamum orientale) lignan preparation containing equivalent amounts of sesamin and episesamin on hepatic fatty acid metabolism was compared in rats, mice and hamsters. Animals were fed on either a diet free of lignan or a diet containing 2 g lignan/kg for 15 d. The lignan preparation greatly increased hepatic activity and the mRNA levels of enzymes involved in fatty acid oxidation, while it strongly down-regulated those of enzymes involved in lipogenesis in rats. In contrast, lignan did not modify these variables in mice and hamsters. Changes observed, if any, were more attenuated in these mice and hamsters than in rats. Sesamin and episesamin concentrations in serum and liver of animals fed on lignan-containing diets were significantly greater (P<0.05) in rats than in mice and hamsters. Moreover, sesamin:episesamin values in tissues were far from that expected from the value in the lignan preparation given to the animals and were dependent on the animal species. Liver microsomes from each animal species degraded sesamin and episesamin in the presence of NADPH. The combined value of sesamin and episesamin degradation rates was lower in rats than in mice and hamsters. In addition, there was considerable diversity in the specificity of the enzyme reaction toward sesamin and episesamin among animal species. The differences in the amounts of lignan remaining in the tissues may account for the species dependence of the physiological activity of sesame lignan in affecting hepatic fatty acid oxidation and synthesis.
Animals↗
Variability in anticancer lignan levels in flaxseed.
Flaxseed and its major mammalian lignan precursor secoisolariciresinol diglycoside have been shown to be protective against chemically induced carcinogenesis in animal models. Although flaxseed is the richest source of mammalian lignan precursors, it is not known whether these levels vary with source. Thus the objective of this study was to determine how lignan levels in flaxseed are affected by variety, growing location, harvest year, and seeding time. Ten varieties of flaxseed (AC Linora, Andro, Flanders, Linott, McGregor, Noralta, NorLin, NorMan, Somme, and Vimy) were subjected to 1) in vitro fermentation with human fecal inoculum for 24 hours under anaerobic conditions to assess mammalian lignan production and 2) high-performance liquid chromatography (HPLC) analysis for secoisolariciresinol levels. Three of these varieties (Linott, McGregor, and NorLin) were grown in four locations, seeded early (May) for three different years, and, in one year, seeded early (May) or late (June). Significant differences in lignan production were observed among the different varieties, ranging from 0.96 mumol/g for Linott to 3.15 mumol/g for Somme flaxseed (p < 0.05). Growing location had significant effects on lignan production from all three varieties. Harvest year significantly affected only the Linott variety (p < 0.05), whereas seeding time had no effect. A significant correlation (r = 0.572, p < 0.003) was observed between lignan values obtained from HPLC and in vitro fermentation methods, indicating that HPLC analysis of flaxseed may be used as a predictor of its lignan production levels. Differences due to variety, harvest location, and harvest year of flaxseed should be taken into consideration when tumorigenesis studies are designed.
Antineoplastic Agents↗