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PubMed1999

Chemical analysis and immunolocalisation of lignin and suberin in endodermal and hypodermal/rhizodermal cell walls of developing maize (Zea mays L.) primary roots.

The composition of suberin and lignin in endodermal cell walls (ECWs) and in rhizodermal/hypodermal cell walls (RHCWs) of developing primary maize (Zea mays L.) roots was analysed after depolymerisation of enzymatically isolated cell wall material. Absolute suberin amounts related to root length significantly increased from primary ECWs (Casparian strips) to secondary ECWs (suberin lamella). During further maturation of the endodermis, reaching the final tertiary developmental state characterised by the deposition of lignified secondary cell walls (u-shaped cell wall deposits), suberin amounts remained constant. Absolute amounts of lignin related to root length constantly increased throughout the change from primary to tertiary ECWs. The suberin of Casparian strips contained high amounts of carboxylic and 2-hydroxy acids, and differed substantially from the suberin of secondary and tertiary ECWs, which was dominated by high contents of omega-hydroxycarboxylic and 1,omega-dicarboxylic acids. Furthermore, the chain-length distribution of suberin monomers in primary ECWs ranged from C(16) to C(24), whereas in secondary and tertiary ECWs a shift towards higher chain lengths (C(16) to C(28)) was observed. The lignin composition of Casparian strips (primary ECWs) showed a high syringyl content and was similar to lignin in secondary cell walls of the tertiary ECWs, whereas lignin in secondary ECWs contained higher amounts of p-hydroxyphenyl units. The suberin and lignin compositions of RHCWs rarely changed with increasing root age. However, compared to the suberin in ECWs, where C(16) and C(18) were the most prominent chain lengths, the suberin of RHCWs was dominated by the higher chain lengths (C(24) and C(26)). The composition of RHCW lignin was similar to that of secondary-ECW lignin. Using lignin-specific antibodies, lignin epitopes were indeed found to be located in the Casparian strip. Surprisingly, the mature suberin layers of tertiary ECWs contained comparable amounts of lignin-like epitopes.

Cell Wall↗
PubMed2001

Quantitative analysis of detailed lignin monomer composition by pyrolysis-gas chromatography combined with preliminary acetylation of the samples.

Detailed quantitative analysis of lignin monomer composition comprising p-coumaryl, coniferyl, and sinapyl alcohol and p-coumaraldehyde, coniferaldehyde, and sinapaldehyde in plant has not been studied from every point mainly because of artifact formation during the lignin isolation procedure, partial loss of the lignin components inherent in the chemical degradative methods, and difficulty in the explanation of the complex spectra generally observed for the lignin components. Here we propose a new method to quantify lignin monomer composition in detail by pyrolysis-gas chromatography (Py-GC) using acetylated lignin samples. The lignin acetylation procedure would contribute to prevent secondary formation of cinnamaldehydes from the corresponding alcohol forms during pyrolysis, which are otherwise unavoidable in conventional Py-GC process to some extent. On the basis of the characteristic peaks on the pyrograms of the acetylated sample, lignin monomer compositions in various dehydrogenative polymers (DHP) as lignin model compounds were determined, taking even minor components such as cinnamaldehydes into consideration. The observed compositions by Py-GC were in good agreement with the supplied lignin monomer contents on DHP synthesis. The new Py-GC method combined with sample preacetylation allowed us an accurate quantitative analysis of detailed lignin monomer composition using a microgram order of extractive-free plant samples.

Acetylation↗
PubMed2003

Elucidation of lignin structure through degradative methods: comparison of modified DFRC and thioacidolysis.

Milled wood and milled wood lignin (MWL) samples were subjected to DFRC and thioacidolysis. Despite the fact that both methods selectively cleave aryl ether bonds, substantial differences in results were obtained. Lignin thioacidolysis gave total molar yields of degradation monomer products in the range of 3.5-7 mol % higher than DFRC. GPC analysis showed that the thioacidolysis-treated lignin was degraded to a lower average molecular weight than that treated by DFRC. Contrary to results reported for lignin model compounds, these results indicate that the DFRC method does not completely or efficiently degrade the lignin polymer. In fact, the DFRC-degraded lignin retained much of the characteristics of the original MWL. Elemental analysis revealed the presence of bromine in the DFRC-treated lignin, and two-dimensional (1)H-(13)C HMQC NMR spectroscopy showed the presence of beta-O-4 linkages in the DFRC-treated lignin. No beta-O-4 interunit linkages were detected in the thioacidolysis-treated lignin. These results are consistent with the lower monomer yields and the higher average molecular weight of the DFRC-treated lignin and indicate inefficiency in the chemistry of the method, probably due to steric constraints of the polymeric nature of lignin.

Chemistry, Organic↗
PubMed2002

Singlet oxygen mediated degradation of lignin--a kinetic study.

Singlet oxygen mediated degradation was carried out on lignin from steam-exploded straw, organosolv lignin and alkali lignin. The lignins were characterized by elemental analysis, UV, FTIR, 1H and 13C NMR, gel permeation chromatography, and thioacidolysis. The kinetics of singlet oxygen degradation were obtained by following the gel permeation chromatograms in the presence of an external standard. This procedure cannot be used for alkali lignin. In the case of steam-exploded and organosolv lignins, the reactions follow zero-order kinetics for the first 4-8 hours; thereafter, the reactions slow down and follow slower zero-order kinetics This behaviour can be explained assuming that easily degradable structures in the outer sphere of lignins are degraded in the first period, while the core lignin is degraded in the second one. The degradation in organosolv lignin is faster than in steam-exploded lignin. Molecular weight distribution and the absence ofguaiacyl units in steam-exploded lignin can give rise to this behaviour. Similar behaviour was obtained in the singlet oxygen degradation of the pulp of steam-exploded straw.

Kinetics↗
PubMed2000

Modified lignin in tobacco and poplar plants over-expressing the Arabidopsis gene encoding ferulate 5-hydroxylase.

Ferulate 5-hydroxylase (F5H) is a cytochrome P450-dependent monooxygenase that catalyses the hydroxylation of ferulic acid, coniferaldehyde and coniferyl alcohol in the pathways leading to sinapic acid and syringyl lignin biosynthesis. Earlier studies in Arabidopsis have demonstrated that F5H over-expression increases lignin syringyl monomer content and abolishes the tissue-specificity of its deposition. To determine whether this enzyme has a similar regulatory role in plants that undergo secondary growth, we over-expressed the F5H gene in tobacco and poplar. In tobacco, over-expression of F5H under the control of the cauliflower mosaic virus 35S promoter increased lignin syringyl monomer content in petioles, but had no detectable effect on lignification in stems. By contrast, when the cinnamate 4-hydroxylase (C4H) promoter was used to drive F5H expression, there was a significant increase in stem lignin syringyl monomer content. Yields of thioglycolic acid and Klason lignin in C4H-F5H lines were lower than in the wild-type, suggesting that F5H over-expression leads to a reduced deposition or an altered extractability of lignin in the transgenic plants. Histochemical analysis suggested that the novel lignin in C4H-F5H transgenic lines was altered in its content of hydroxycinnamyl aldehydes. Transgenic poplar trees carrying the C4H-F5H transgene also displayed enhanced lignin syringyl monomer content. Taken together, these data show that hydroxylation of guaiacyl-substituted lignin precursors controls lignin monomer composition in woody plants, and that F5H over-expression is a viable metabolic engineering strategy for modifying lignin biosynthesis in forest species.

Arabidopsis↗
PubMed2005

Molecular composition of leaves and stems of genetically modified Bt and near-isogenic non-Bt maize--characterization of lignin patterns.

Transformation of crops, including maize (Zea mays L.), with the cry1Ab gene from Bacillus thuringiensis to combat lepidopteran pests results in pleiotropic effects regarding lignin biosynthesis. Lignin patterns in stems and leaves of two genetically modified Bt-maize varieties (Novelis T and Valmont T) were studied along with their non-Bt near-isolines (Nobilis and Prelude, respectively). Molecular-level based thermochemolysis using tetramethylammonium hydroxide (TMAH) in combination with gas chromatography-mass spectrometry (GC-MS) was used to quantitate the total lignin contents and to identify monomeric lignin subunits including p-hydroxyphenyl (P), guaiacyl (G), and syringyl (S) moieties. The results were supplemented and confirmed by cupric oxide oxidation. The stems of the transgenic lines had higher concentrations of total lignin than the respective isogenic lines: Valmont T/Prelude by 18% and Novelis T/Nobilis by 28%. In contrast, differences in the total lignin concentration of leaves between the transgenic and the respective near-isogenic lines were marginal. There were significant modifications in the ratio of p-hydroxyphenyl/guaiacyl/syringyl molecular marker units of stem lignin between transgenic and isogenic lines. The guaiacyl units (in particular the G18 marker) accounted chiefly for the higher total lignin contents in the transgenic lines. The leaf lignin patterns did not show significant differences in molecular markers between isogenic and transgenic lines. TMAH-induced thermochemolysis--conducted in both the on-line and off-line modes--provided detailed information on the molecular composition of lignin, thus proving superior to the established "wet chemistry" methods of lignin determination.

Analysis of Variance↗
PubMed1986

Influence of lignin on digestibility of forage cell wall material.

One-hundred-ninety-four grass samples, representing eight species, were used to determine the relationships of in vitro forage dry matter, cell wall, hemicellulose and cellulose digestibilities with lignin concentration. Linear regressions indicated that dry matter digestion was inhibited to a lesser degree (P less than .05) by lignin concentration than was cell wall digestion. Results for linear regressions of hemicellulose and cellulose digestibilities as functions of lignin concentration showed a greater (P less than .05) effect of lignin on cellulose digestion. Smooth bromegrass and switchgrass were collected at both Clay Center and Mead, NE; for all digestibility measures, the Clay Center samples gave stronger (P less than .05) negative correlations with lignin. A comparison of linear and curvilinear models indicated that, for all digestion measurements, the curvilinear model was a better (P less than .05) description of relationships with lignin concentration. For all digestibility measures, lignin's inhibiting effect declined at higher lignin concentrations. The curvilinear models did not show significant differences among the digestibility measures for effect of lignin. The demonstration that the forage digestibility response to lignin's inhibitory effect is curvilinear in nature suggests that the mechanism of lignin's inhibition is complex.

Animal Feed↗
PubMed2006

Fiber and lignin analysis in concentrate, forage, and feces: detergent versus enzymatic-chemical method.

Hemicelluloses, cellulose, and lignin contents of contrasting feeds, with emphasis on concentrate ingredients and complete concentrates, were analyzed using the Van Soest detergent procedure (analyzing neutral detergent fiber, acid detergent fiber, and acid detergent lignin) and the enzymatic-chemical procedure (analyzing cellulose, soluble and insoluble noncellulosic polysaccharides, and Klason lignin). Also, feces from cows fed concentrates differing in carbohydrate composition were analyzed by the 2 procedures. The correlation between acid detergent lignin and Klason lignin was significant, but not as close as the one between individual structural polysaccharides measured with the 2 procedures. The correlation between the results of the 2 procedures was highly significant for apparent cellulose digestibility, as were the correlations between digestibilities of hemicelluloses with total as well as with insoluble noncellulosic polysaccharides. The relationship between dietary lignin content and fiber digestibility was weak. The exclusion of a group of cows fed a concentrate with apple pulp, however, improved the respective correlations. Klason lignin correlated more closely with the measured fiber digestibility than acid detergent lignin. The study showed that results of the detergent method were comparable to those of the enzymatic-chemical method with cellulose, hemicelluloses, and their digestibilities. However, acid detergent lignin was much lower than Klason lignin. When the carbohydrate composition of concentrate varied widely, lignin was not suitable for the prediction of fiber digestibility.

Amylases↗
PubMed2004

Detection in situ and characterization of lignin in the G-layer of tension wood fibres of Populus deltoides.

The occurrence of lignin in the additional gelatinous (G-) layer that differentiates in the secondary wall of hardwoods during tension wood formation has long been debated. In the present work, the ultrastructural distribution of lignin in the cell walls of normal and tension wood fibres from poplar (Populus deltoides Bartr. ex Marshall) was investigated by transmission electron microscopy using cryo-fixation-freeze-substitution in association with immunogold probes directed against typical structural motifs of lignin. The specificity of the immunological probes for condensed and non-condensed guaiacyl and syringyl interunit linkages of lignin, and their high sensitivity, allowed detection of lignin epitopes of definite chemical structures in the G-layer of tension wood fibres. Semi-quantitative distribution of the corresponding epitopes revealed the abundance of syringyl units in the G-layer. Predominating non-condensed lignin sub-structures appeared to be embedded in the crystalline cellulose matrix prevailing in the G-layer. The endwise mode of polymerization that is known to lead to these types of lignin structures appears consistent with such an organized cellulose environment. Immunochemical labelling provides the first visualization in planta of lignin structures within the G-layer of tension wood. The patterns of distribution of syringyl epitopes indicate that syringyl lignin is deposited more intensely in the later phase of fibre secondary wall assembly. The data also illustrate that syringyl lignin synthesis in tension wood fibres is under specific spatial and temporal regulation targeted differentially throughout cell wall layers.

Animals↗
PubMed2006

Evaluation of spray-dried lignin-based formulations and adjuvants as solar protectants for the granulovirus of the codling moth, Cydia pomonella (L).

Commercial formulations of the codling moth, Cydia pomonella L., granulovirus (CpGV) are limited by their short residual activity under orchard conditions in the Pacific Northwest. We evaluated spray-dried lignin-encapsulated formulations of CpGV for improved solar stability based on laboratory bioassays with a solar simulator and in field tests in an infested apple orchard. In laboratory tests, aqueous lignin formulations containing a high dosage of 3 x 10(10) occlusion bodies (OB)/L, with and without the additives titanium dioxide (TiO(2)) and sugar, provided significant solar protection of virus, i.e., mortality of codling moth exposed to lignin formulations that had been irradiated with 9.36 x 10(6) joules/m(2) was 92-94%, compared with 66-67% from a glycerin-stabilized product (Cyd-X) or suspension of pure unformulated virus at the same rates. By comparison, a lower dosage of the lignin formulation (3 x 10(8)OB/L) did not provide significant solar protection. Equivalent dosage-dependent patterns in solar protection were observed in further tests with the lignin formulation, when an intermediate (3 x 10(9)OB/L) as well as the low dosage provided no solar protection. Equivalent rates of a blank lignin formulation (containing no virus) did not affect larval mortality, suggesting a protective effect of the lignin on the virus at the high rate. The use of several spray adjuvants, 'NuFilm-17' and 'Organic Biolink' (sticker-spreaders at 0.06% v/v), 'Raynox' (sunburn protectant at 5% v/v), and 'Trilogy'(neem oil at 1% v/v) did not provide solar protection of a commercial CpGV preparation in laboratory tests. In season long orchard tests (Golden Delicious), the lignin formulation of CpGV applied at 6.57 x 10(12)OB/ha did not significantly improve control of codling moth or protection of fruit compared with Cyd-X at equivalent rates. Our studies show that lignin-based CpGV formulations provided solar protection at relatively high virus dosages. The testing of lignin formulations containing reduced virus concentrations may allow virus solar protection to be achieved at more economical rates.

Animals↗
PubMed2006

Structure of lignins in developing xylem of Norway spruce.

The developing xylem in a Norway spruce (Picea abies) clone was investigated during a growth season and compared to lignin from sapwood of the same tree clone. Klason and acid-soluble lignin contents were determined as well as the carbohydrate monomer distribution and protein content. By analyzing lignin thioacidolysis products, it was shown that only guaiacyl units could be detected in the materials, and the relative amount of beta-O-4' bonds was assessed. Monomeric and selected dimeric lignin products were identified by mass spectrometry. The specimens were embedded and thin sections examined by microscopy to determine the state of cell differentiation in the samples. In the spring and early summer, growth was very rapid and the intention was to collect tissue in which exclusively the middle lamella/primary cell wall had begun to lignify. Combining data regarding Klason lignin, protein content and carbohydrate monomer distribution with microscopy, it was found that the developing xylem sample from mid-June contained lignin from exclusively middle lamella/primary wall. The Klason lignin content in the developing xylem during the growth season was 20%, 5% and 10% in April, June and August, respectively. Thioacidolysis showed that the lignin had more condensed structures than lignin from the reference Norway spruce clone wood. Mass spectrometry showed that the developing xylem specimens from June and August contained more lignin structures with end-groups than the reference sample. These results suggest that lignification in the cambial layer and early developing xylem may take place more in a bulk fashion during the summer.

Lignin↗
PubMed2002

Studies on the effect of ball milling on lignin structure using a modified DFRC method.

The structures of milled wood lignin (MWL), cellulolytic enzyme lignin (CEL), and residual lignin (REL) from a loblolly pine were analyzed using a modified derivatization followed by reductive cleavage (DFRC) method developed to allow the quantitative determination of three different structural monomeric products originating in lignin: phenolic beta-O-4, alpha-O-4, and etherified beta-O-4 structures. Results show that MWL and CEL are structurally identical, with an increased phenolic beta-O-4 content compared to that of the original Wiley milled wood. These results indicate that the portion of lignin linked to carbohydrates and that not linked to carbohydrates are structurally the same. Modified DFRC analysis of the effect of ball milling on the structure of lignin in wood, MWL, CEL, and REL indicate that vibratory ball milling does not change the lignin structure provided certain precautions are taken. Specifically, dry vibratory ball milling under a nitrogen atmosphere causes substantial structural changes including condensation, whereas vibratory ball milling in toluene had little effect on the lignin structure. This indicates that the structural differences observed in MWL and CEL arise because of the extraction procedure, which preferentially extracts phenolic lignin structures. MWL and CEL are representative of the total lignin in wood; however, due primarily to the solvent extraction process, higher phenolic hydroxyl contents are observed. Nitrobenzene oxidation showed structural results similar to those from the modified DFRC method.

Chemistry, Organic↗
PubMed2005

Characterization of dietary fiber lignins from fruits and vegetables using the DFRC method.

Insoluble fiber fractions from 11 fruits and vegetables were investigated for their lignin composition using the derivatization followed by reductive cleavage (DFRC) methodology. To enrich lignin contents and to minimize polysaccharide excess that led to nonanalyzable DFRC chromatograms, the insoluble fibers were degraded by a carbohydrolases mixture. The residues that were found to be representative for the insoluble fiber lignins were analyzed. The investigated fibers differ considerably in their lignin contents and also in their lignin compositions. With the exception of radish fiber, only trace amounts (or none) of the products resulting from p-hydroxyphenyl units were detected. Lignins noticeably differed in the ratio of the DFRC products resulting from syringyl units (S) and guaiacyl (G) units (G/S ratios ranged from approximately 39 to 0.2). The insoluble fiber lignins were classified as G-rich lignins (G/S ratio > 3; carrot, spinach, kiwi, curly kale, radish, and asparagus), S-rich lignins (S/G ratio > 3; rhubarb), or balanced lignins (0.3 < G/S ratio < 3; pear, apple, small radish, and kohlrabi). Information about further structural characteristics, for example, cinnamyl endgroups, was obtained from the analysis of DFRC minor products.

Acetates↗
PubMed1999

Characterization of residual lignin after SO(2)-catalyzed steam explosion and enzymatic hydrolysis of Eucalyptus viminalis wood chips.

The lignin component found in both water insoluble (WI) and water and alkali insoluble (WIA) fractions derived from SO(2)-impregnated steam-exploded eucalyptus chips (SEE) was isolated and characterized. Dioxane lignins with a sugar content lower than 2% (w/w) were obtained after each material was treated with commercial cellulases. The C9 formulas of both SEE-WI and SEE-WIA dioxane lignins were C(9)H(6.83)N(0.04)O(2.24)(OCH(3))(1.21)(OH(aro))(0.56)(OH(ali))(0. 77) and C(9)H(8.65)N(0.29)O(1.97)(OCH(3))(0.90)(OH(aro))(0. 46)(OH(ali))(1.02), respectively. The weight-average molecular weight (M(w)) of the SEE-WI lignin corresponded to 3.85 kDa, whereas the SEE-WIA lignin had an M(w) of 3.66 kDa for the same polydispersity of 2.4. The SEE-WIA lignin was shown to be more thermally stable than the SEE-WI lignin, requiring temperatures in the range of 520 degrees C for complete degradation. FTIR and (1)H NMR analyses of both untreated and peracetylated lignin fractions showed that (a) the alkali insoluble lignin contained a relatively higher degree of substitution in aromatic rings per C9 unit and that (b) alkaline extraction removed lignin fragments containing appreciable amounts of phenolic hydroxyl groups.

Cellulase↗
PubMed2001

Improvement of in-rumen digestibility of alfalfa forage by genetic manipulation of lignin O-methyltransferases.

Lignin inhibits forage digestibility by ruminant animals, and lignin levels and the proportion of dimethylated syringyl (S) lignin monomers increase with progressive maturity in stems of forage crops. We generated transgenic alfalfa (Medicago sativa L.) with reduced lignin content and altered lignin composition. Down-regulation of caffeic acid 3-O-methyltransferase (COMT) reduces lignin content, accompanied by near total loss of S lignin, whereas down-regulation of caffeoyl coenzyme A 3-O-methyltransferase (CCoAOMT) reduces lignin content without reduction in S lignin. These changes are not accompanied by altered ratios of cell wall polysaccharides. Analysis of rumen digestibility of alfalfa forage in fistulated steers revealed improved digestibility of forage from COMT down-regulated plants, but a greater improvement in digestibility following down-regulation of CCoAOMT. The results indicate that both lignin content and composition affect digestibility of alfalfa forage, and reveal a new strategy for forage quality improvement by genetic manipulation of CCoAOMT expression.

Animals↗
PubMed1989

Lignocellulose degradation and subsequent metabolism of lignin fermentation products by the desert black Bedouin goat fed on wheat straw as a single-component diet.

Bedouin goats were fed on wheat straw as a single-component diet under two watering regimens, drinking once daily or once every 4 d, in order to clarify whether lignin-degradation products were absorbed, metabolized and excreted in urine. Acid-soluble lignin accounted for 220 g/kg total lignin, its digestibility was the highest (0.87) and was unaffected by water deprivation. Acid-insoluble lignin accounted for 780 g/kg total lignin and its digestibility increased during water deprivation from 0.21 to 0.41. Alkali-soluble lignin accounted for 320 g/kg total lignin and its digestibility increased during water deprivation from 0.44 to 0.53. Digestibility of structural carbohydrate was considerably higher than that observed in other domesticated ruminants fed on wheat straw. It responded positively to water deprivation, increasing from 0.63 to 0.73 with cellulose and from 0.61 to 0.68 with hemicellulose. The amount of urinary aromatic acids, mainly in the form of hippuric acid, considerably exceeded the potential contribution of any non-lignin component which might affect the excretion of aromatic acids. A considerable percentage (71-76) of the apparently digested lignin was not accounted for as soluble phenolic compounds in faeces or as aromatic acids in urine, and hence was apparently completely metabolized. Lignin is a key substrate which is extensively digested in goats fed on low-quality forage, with subsequent absorption of endproducts. This enhanced the availability of structural carbohydrates for fermentation and was associated with excretion of high-energy metabolites in the form of benzoic and hippuric acids.

Animal Feed↗
PubMed1998

Free radical-scavenging properties of lignin.

Lignin is one of the major components of dietary fiber. It is a complex hydrophobic molecule that typically occurs in cell walls with heteroxylans. Our experimental data show that lignin is a free radical scavenger. When the NADH-phenazine methosulfate-nitro blue tetrazolium free radical-producing system is used, an alkali-lignin concentration of 46.29 micrograms/ml that causes 50% inhibition of uric acid production by xanthine oxidase (IC50) is a scavenger of superoxide anion radicals. Spectrophotometric assay has shown that alkali-lignin with an IC50 of 59.08 micrograms/ml inhibits the activity of xanthine oxidase, one of the enzymes related to the production of superoxide anion radicals, and presents a mixed-type noncompetitive inhibition pattern. Using the deoxyribose method, we have found that alkali-lignin is a hydroxyl radical scavenger with an IC50 of 250 micrograms/ml, and using the thiobarbituric acid method, we can see that alkali-lignin inhibits nonenzymatic and enzymatic lipid peroxidation with an IC50 of 72 and 100 micrograms/ml, respectively. Alkali-lignin also hinders the activity of glucose-6-phosphate dehydrogenase, another enzyme related to the generation of superoxide anion radicals, with an IC50 of 123.6 micrograms/ml, and obstructs the growth and viability of cancer (HeLa) cells in a dose-dependent manner. Our experimental results suggest another mechanism whereby the free radical-scavenging activity of lignin in dietary fiber may be involved in the fiber-colon cancer interaction. We also suggest that the ability of dietary fiber to protect against colon cancer may be partly determined by the amount of lignin in dietary fiber as well as the free radical-scavenging ability of lignin.

Animals↗
PubMed1998

Dietary lignin, and insoluble fiber, enhance uterine cancer but did not influence mammary cancer induced by N-methyl-N-nitrosourea in rats.

Previous investigations suggested potential breast cancer-preventive properties of dietary fiber from cabbage. The purpose of the present investigation was to determine whether lignin, a component of cabbage fiber, would protect against mammary carcinogenesis by N-methyl-N-nitrosourea (MNU) in Sprague-Dawley rats. A six-week study was conducted using diets containing 0.5-5% dietary wood lignin (a readily available, purified source). These diets were well tolerated by the rats, and a carcinogenesis study using 5 mg MNU/100 g body wt i.v. at 50 days of age was conducted, with the 2.5% lignin diet fed from 6 through 8 weeks of age followed by 5% lignin diet until 20 weeks after MNU. Dietary lignin and MNU treatment increased food consumption (p < 0.05), and body weight was slightly reduced at 10 and 20 weeks after MNU in the MNU-5% lignin diet group (p < 0.05). Serum estradiol was not altered by dietary lignin or MNU treatment, but uterine weights were highest in the MNU-control diet group 4 and 12 weeks after MNU. Expression of creatine kinase B, and estrogen-responsive gene, was lower in eh uteri of the MNU-lignin diet group than in other groups at 20 weeks. Mammary carcinogenesis was not altered by dietary lignin. However, uterine endometrial adenocarcinoma was observed only in the MNU-lignin diet group (4 carcinomas/40 effective rats) (p < 0.05).

Adenocarcinoma↗