Spruce Knots Research Articles

Beer and beer-based beverage contain lignans.

Lignans are members of a broad group of plant phenols that can positively affect human health. They occur in negligible quantities in processed foodstuffs such as lager beer. The aim of this work was to utilize the high levels of lignans in the knots of spruce trees (Picea abies) to increase the lignans content in beer, without negatively impacting the natural taste and aroma. By means of lignans addition in the forms of spruce knot chips or different extracts made from spruce knots during the wort boiling were produced beer and beer-based beverages with lignans content ranging from 34 to 174mg/L.

9-Norlignans: Occurrence, Properties and Their Semisynthetic Preparation from Hydroxymatairesinol.

Lignans, neolignans, norlignans and norneolignans constitute a large class of phenolic natural compounds. 9-Norlignans, here defined to contain a β–β’ bond between the two phenylpropanoid units and to lack carbon number 9 from the parent lignan structure, are the most rarely occurring compounds within this class of natural compounds. We present here an overview of the structure, occurrence and biological activity of thirty-five 9-norlignans reported in the literature to date. In addition, we report the semisynthetic preparation of sixteen 9-norlignans using the natural lignan hydroxymatairesinol obtained from spruce knots, as starting material. 9-Norlignans are shown to exist in different species and to have various biological activities, and they may therefore serve as lead compounds for example for the development of anticancer agents. Hydroxymatairesinol is shown to be a readily available starting material for the preparation of norlignans of the imperanene, vitrofolal and noralashinol family.

Musts with Increased Lignan Content Through Addition of Lignan Extracts

Red and white grape musts were enriched with 7-hydroxymatairesinol (HMR), which is the main lignan contained in spruce knots. Lignan enrichment was achieved by adding a spruce knot ethanol extract. Enriched musts were stored for 12 months and during storage must samples were periodically analyzed for HMR and alpha-conidendrin content, antioxidant activity, total polyphenols, and anti-mutagenicity. The data were statistically evaluated in order to determine the influence of grape type, quantity of added lignan extracts, addition of sugar, method of preservation and storage time on the quantity of lignans added, antioxidant activity, total polyphenols, and anti-mutagenicity. Lignan content was significantly influenced by the addition of lignan extracts. After storage, lignan content had changed only moderately and the added lignans were stable in the stored musts. Total polyphenol content and antioxidant activity of grape musts were significantly increased by the type of must grape and by thermomaceration. Thermomacerated red musts exhibited higher anti-mutagenicity compared to thermomacerated white musts, independent of lignan addition.

Enhanced extraction and biological activity of 7-hydroxymatairesinol obtained from Norway spruce knots using aqueous solutions of ionic liquids

Biocompatible aqueous solutions of ILs rich in 7-hydroxymatairesinol (HMR) can be safely used in cosmetic and nutraceutical applications.

Wines with increased lignan content by the addition of lignan extracts

Red and white wines [Grüner Veltliner white wine and Blue Limberger (Blaufränkisch) red wine (vintage 2013)] were enriched with lignan hydroxymatairesinol originated from spruce knots. These spruce knots with removed resin were extracted with ethyl alcohol of agricultural origin. Ethanol extracts of lignans were then used to enrich wine sorts. Enriched wines were stored for 13 months. At 2, 6, and 13 months, samples were taken and subjected to a variety of analyses and sensory evaluations. Analyses included 7-hydroxymatairesinol and alpha-conidendrin lignan content, antioxidant activity (as determined by FRAP), total polyphenols, and sensory evaluation. The obtained data were evaluated using the analysis of variance to determine which factors e.g. wine type, quantity of added lignan extracts, additional sugar, method of preservation, and storage time had the most significant influence on lignan content, antioxidant activity and polyphenol content. In all cases the lignan content in the wines was significantly influenced by the addition of lignan extracts. After one year of storage, lignan contents changed only moderately and added lignans were stable in stored wines. Total polyphenol content in wines and the antioxidant activity of wines were significantly influenced by the type of wine (i.e., red or white). The presented method of wine enrichment with lignans opens the door for the production of extra quality wines.

Musts with an increased content of lignans from added spruce knot chips

Red and white musts were enriched with the lignan hydroxymatairesinol, which is the main lignan contained in spruce knots. Chips from the milled spruce knots were then used to enrich grape musts. After enrichment, the musts were stored and samples were taken in 1, 5, 9, and 12 months. The samples were subjected to a variety of analyses and sensory evaluations. Analyses included hydroxymatairesinol and alpha-conidendrin content, antioxidant activity (determined by the FRAP method), content of total polyphenols, sensory evaluation (intensity of woody aroma, intensity of bitterness and astringent taste, and consumer acceptability), and must antimutagenicity. The analysis of variance allowed predicting which factors such as grape type, quantity of added wood chips, sugar addition, method of preservation, and storage time had the most significant influence on the analytical parameters (lignan content, antioxidant activity, and total polyphenol content). In all cases lignan content in the musts was significantly influenced by the addition of spruce wood chips. Total polyphenol content in the musts was significantly affected by the type of musts and by heat treatment (time of thermomaceration). Evaluation of must antimutagenicity showed that all samples, except the sample of white musts after thermomaceration without holding at temperature and without adding chips (10 g/20 kg mash), inhibited mutagenicity.

Structure sensitivity in heterogeneous catalysis with noncompetitive adsorption of reactants: Selective oxidation of lignan hydroxymatairesinol to oxomatairesinol over gold catalysts

Abstract Structure sensitivity in heterogeneous catalytic oxidative dehydrogenation of lignan hydroxymatairesinol (HMR) extracted from Norway spruce knots was investigated over a series of alumina-supported gold catalysts. A mathematical model was developed based on the concept of noncompetitive adsorption of reactants. The model, being consistent with kinetic regularities, such as reaction orders in reactants, explains well the dependence of catalytic activity on the gold cluster size.

Lignans 7‐hydroxymatairesinol and 7‐hydroxymatairesinol 2 exhibit anti‐inflammatory activity in human aortic endothelial cells

In the present study, we evaluated the anti-inflammatory properties of several plant lignans most commonly distributed in foods. 7-Hydroxymatairesinol (HMR) and its major isomer 7-hydroxymatairesinol 2 (HMR2), lariciresinol, secoisolariciresinol, and pinoresinol, isolated from Norway spruce knots were examined. We investigated the anti-inflammatory effects of lignans on tumor necrosis factor-α-treated human aortic endothelial cells by measuring the expression of intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 by cell ELISA and the adhesion of U937 monocytes to activated endothelial cells using a cell adhesion assay. Among the lignans studied, HMR and HMR2 significantly reduced intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 levels as well as the adhesion of U937 to endothelial cells. To further characterize the molecular mechanisms involved in this regulation, the effect of HMR and HMR2 on nuclear factor-κB, SAPK/c-Jun NH2-terminal kinase and extracellular signal regulated kinase phosphorylation was assessed. Our results demonstrated that the lignans HMR and HMR2, dominant in cereals such as in wheat, triticale, oat, barley, millet, corn bran, and in amaranth whole grain, exhibit strong anti-inflammatory properties in endothelial cells, at least in part, through attenuation of nuclear factor-κB and extracellular signal regulated kinase phosphorylation.

Kinetics of the selective oxidation of the lignan hydroxymatairesinol to oxomatairesinol over Au/Al2O3 catalysts

Lignan hydroxymatairesinol (HMR) extracted from Norway spruce knots was oxidized to the lignan oxomatairesinol (oxoMAT) in a semi-batch glass reactor under the atmospheric pressure in the presence of oxygen (5–49vol.% in nitrogen) over 2wt.% Au/Al2O3 catalyst, using propan-2-ol-water mixture as a solvent. The following kinetic parameters were determined: adsorption constants, rate constants, reaction order for reagents, and energy of activation. Through the parameter estimation the experimental data were fitted to the advanced kinetic model demonstrating a good correlation between the model and experiments.

Describing the inverse dependence of hydrogen pressure by multi-site adsorption of the reactant: Hydrogenolysis of hydroxymatairesinol on a Pd/C catalyst

The hydrogenolysis of the lignan hydroxymatairesinol (HMR), extracted from Norway spruce knots, to matairesinol (MAT) was done in a stainless steel autoclave using a 5% Pd/C. The influence of hydrogen pressure (4–40bar) was studied and the hydrogenolysis reaction rate was proved to decrease at higher hydrogen pressure. This was explained by competitive adsorption of HMR and hydrogen, where HMR adsorbs on several Pd atoms. The kinetic results were described with a model applying multi-site adsorption for the reactant, where the number of Pd surface atoms needed for the adsorption of a single HMR molecule was determined to 20 using molecular modelling. The values of the rate and adsorption constants were estimated using a parameter estimation program. The kinetic model explained the experimental data well.

Estrogenic activity of 7-hydroxymatairesinol potassium acetate (HMR/lignan™) from Norway spruce ( Picea abies) knots and of its active metabolite enterolactone in MCF-7 cells

Lignans are plant polyphenols which may possess anticancer, antioxidant, antimicrobial, anti-inflammatory and immunomodulatory activities. In particular, the lignan 7-hydroxymatairesinol (HMR/lignan™, HMR) is a novel precursor of the mammalian lignan enterolactone (EL). In the present study, we investigated the estrogenicity of HMR and of EL in comparison to estradiol (E2), by measuring their effects on growth and apoptotic markers in the human estrogen-sensitive cell line MCF-7. HMR, EL and E2 concentration-dependently increased the percentage of MCF-7 cells in the S phase of the cell cycle, with the following relative potencies: E2 ≅ EL ≫ HMR, and efficacies: E2 > HMR ≫ EL. Treatment of MCF-7 cells with either HMR, EL or E2 also increased the Bcl-2/Bax mRNA ratio. The effects of HMR and EL were reduced in the presence of the estrogen receptor (ER) antagonist tamoxifene. We conclude that both HMR and its metabolite EL are endowed with estrogenic activity, which is likely to be exerted through the contribution of ER-dependent pathways and to target the same intracellular mechanisms acted upon by E2. The estrogenicity of HMR and EL is however milder than that of E2, as indicated by the lower potencies and efficacies of both lignans. The present results support the notion that dietary supplementation with HMR may result in a mild estrogenic activity, both directly and by providing a suitable source for endogenous EL.

The influence of acidity of carbon nanofibre-supported palladium catalysts in the hydrogenolysis of hydroxymatairesinol

The lignan hydroxymatairesinol (HMR, extracted from Norway spruce knots) was hydrogenolysed to matairesinol (MAT) over palladium supported by carbon nanofibres (Pd/CNF) in 2-propanol at 70 °C under hydrogen flow. The influence of support acidity on the activity and the selectivity to MAT was studied. The acidity of the Pd/CNF catalyst was varied by heat-treatment at different temperatures in nitrogen flow. The catalysts were characterized by transmission electron microscopy (TEM), inductively coupled plasma emission mass-spectrometry (ICP-MS, metal content), H2-chemisorption (dispersion, metal particle size), and titration using NaOH. A more acidic support material was more active and selective to the desired product MAT. The major byproduct was 7-iso-propoxymatairesinol resulting from a reaction of the solvent with HMR over the acid sites on the support. The hydrogenolysis of HMR to MAT requires both the presence of metal and acidity.

Reactions of hydroxymatairesinol over supported palladium catalysts

In this work, hydroxymatairesinol (extracted from Norway spruce knots) was hydrogenolyzed to matairesinol over palladium impregnated H-Beta-300, H-Beta-150, H-Beta-25, H-Beta-11, H-Y, H-Mordenite, H-MCM-41, H-ZSM-5, SiO 2, and Al 2O 3. H-Beta-25 without palladium was also investigated. The hydrogenolysis was performed in 2-propanol at 70 °C under hydrogen and nitrogen atmospheres in a stirred glass reactor. The catalysts were characterized by nitrogen physisorption, direct current plasma atomic emission spectrometry, X-ray powder diffraction, CO pulse chemisorption, transmission electron microscopy, and Fourier transform infrared spectroscopy (pyridine adsorption). Palladium on H-Beta with different acidities was tested; the results showed that the reaction rate was inversely proportional to the acidity. However, Brønsted acid sites are needed for the reaction, because palladium on SiO 2 and Al 2O 3 is not active. In addition to the acidity, a metal is needed; the H-Beta-25 support without palladium displays no activity.

Bioactive phenolic substances in industrially important tree species. Part 1: Knots and stemwood of different spruce species

Abstract Knots (i.e., branch bases inside tree stems) in spruce trees contained remarkably higher concentrations of lignans and oligolignans than the adjacent stemwood. The amount of lignans in some knots exceeded 10% (w w−1) and some knots contained hundreds of times more lignans than the heartwood in the same tree. However, there were large variations between different species and even between different knots in the same tree. 7-Hydroxymatairesinol was the predominant lignan in knots of Picea abies, P. glauca, P. koraiensis, P. mariana, and P. omorika, while liovil and secoisolariciresinol dominated in P. sitchensis and P. pungens. The lignans occur in free form in knots and are easily extracted with polar solvents. In addition to the true lignans, especially the knots contained large amounts of lignan-related oligomeric aromatic substances, here called oligolignans, consisting of three or four phenylpropane units. 7-Hydroxymatairesinol, but also other lignans, could be extracted in large scale from spruce knots at pulp and paper mills. Other potentially important lignans could be produced from 7-hydroxymatairesinol by semisynthesis. The ready availability of large amounts of lignans and oligolignans now enables research to assess their bioactivity and provide the basis for applications in medicine and nutrition or as natural antioxidants and antimicrobial agents in a variety of technical products.

Lignans and Lipophilic Extractives in Norway Spruce Knots and Stemwood

Summary The hydrophilic and lipophilic extractives in the heartwood of knots from 7 Norway spruce trees were analysed by GC, GC-MS and HPSEC. The knots contained extremely large amounts of lignans, 6–24% (w/w), with hydroxymatairesinol comprising 65–85% of the lignans. Even the knots of the young trees contained 4–8% (w/w) of lignans. The variation in the amount of lignans was large among knots, both within a single tree and between trees. In addition to the lignans, knots also contained 2–6% (w/w) of a complex mixture of lignan-like compounds with 3, 4 and even up to 6 phenyl propane units, here called oligolignans. The amounts of lignans in the knots were similar in the radial direction from the pith into the outer branch, but decreased dramatically outwards in the branch, almost disappearing after 10–20 cm. The ratio of the 2 epimers of hydroxymatairesinol differed between different knots and even within the knot. A new spruce lignan, nortrachelogenin, or its enantiomer, wikstromol, was detected in knots from trees in northern Finland as opposed to samples from southern Finland. The amount of lipophilic extractives was small compared to the amount of hydrophilic extractives in the knots. Five of the dead knots contained more resin acids and free diterpenyl alcohols than ordinary stemwood. In the other knots, the amount of lipophilic extractives was on the same level as stem heartwood. The stem sapwood contained larger amounts of esterified fatty acids than the knots.

Knots in trees – A new rich source of lignans

Recent research in our group has revealed that knots, i.e. the branch bases inside tree stems, commonly contain 5–10% (w/w) of lignans. Norway spruce (Picea abies) knots contain as much as 6–24% of lignans, with 7-hydroxymatairesinol (HMR) as the predominant (70–85%) lignan. Some other spruce species also contain HMR as the main lignan, but some spruce species have also other dominating lignans. Most fir (Abies) species contain secoisolariciresinol and lariciresinol as the main lignans. Lignans occur also in knots of pines (Pinus spp.), although in lower amounts than in spruces and firs. Scots pine (Pinus silvestris) knots were found to contain 0.4–3% of lignans with nortrachelogenin as the main lignan. Lignans have been identified also in knots of some hardwoods, although flavonoids are more abundant in hardwoods. Knots are detrimental in the manufacture of pulp and paper and should preferably be removed before pulping. This is possible using a recently developed industrially applicable process called ChipSep. Recent research has also established novel synthetic routes to several lignans, such as matairesinol, secoisolariciresinol, lariciresinol and cyclolariciresinol, starting from hydroxymatairesinol by applying fairly straight-forward chemical transformations. We conclude that wood knots in certain spruce and fir species constitute the richest known source of lignans in nature. The lignans occur in knots in free form and are easily extracted by aqueous ethanol, or even by water. Not only HMR, but also other potentially valuable lignans, could be produced in a scale of hundreds of tons per year by extraction of knots separated from wood chips at pulp and paper mills.