Abstract:
The present invention relates to a method for isolating of phenolic substances or juvabiones from wood comprising knotwood, said method comprising the steps of 
     a) extracting  
     i) the over-sized chip fraction obtained by screening chipped wood, or  
     ii) a knot-rich sub-fraction obtained from said over-sized chip fraction, or  
     iii) knotwood obtained as residue in finishing of mechanical wood products  
     with a polar solvent, and  
     b) recovering the extract.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a method for isolating chemical substances, i.e. phenolic substances or juvabiones from wood comprising knotwood.  
         BACKGROUND OF THE INVENTION  
         [0002]    The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.  
           [0003]    It is known that vegetabilic sources, including wood, contain phenolic substances which are more or less hydrophilic. The phenolic substances derived from wood are flavonoids, lignans and stilbenes. In spruce wood the dominant group is lignans while flavonoids and stilbenes are the dominant phenolic substances in pine wood and hardwoods. Freudenberg and Knof (1) identified already in 1957 many different lignans in Norway spruce, including e.g. hydroxymatairesinol, matairesinol, conidendrin, pinoresinol, oxomatairesinol, lariciresinol, allohydroxymatairesinol and liovil. In addition to these lignans, isolariciresinol, secoisolariciresinol, picearesinol and conidendric acid have been isolated from spruce (2).  
           [0004]    Pinosylvin (a stilbene) and flavonoids have been identified in pine wood. The flavonoids aromadendrin and taxifolin have been isolated from larch wood. Both stilbenes and flavonoids have been isolated from hardwoods. Many of these phenolic compounds have been reported to possess valuable therapeutical properties, particularly as antitumour agents and antioxidants. (S Nishibe, 1997, (3)), J D Ford et al 1999 (4) and N M Saarinen et al 2000 (5)).  
           [0005]    Juvabiones are a group of cyclohexane derivatives and are useful e.g. as insecticides.  
           [0006]    Before this invention, it has not been known that the knots and branches of the trees are particularly rich in flavonoids and stilbenes, compared to other parts of the tree.  
           [0007]    Although it is been mentioned in the literature (2) that certain lignans, particularly hydroxymatairesinol, occur in wood and branches, so far no practically useful method has been presented for isolating such compounds from wood.  
         SUMMARY OF THE INVENTION  
         [0008]    This invention in based on the idea of combining the isolation of phenolic substances or juvabiones from wood with the utilization of wood in manufacturing of pulp or various mechanical wood products. The aim of this invention is thus to i) provide a practically useful source for these useful chemical substances and ii) improve the economy for the manufacturing processes of pulp or mechanical wood products in that by-products, hitherto used only for energy production, are offered a new use as source for phenolic substances and juvabiones.  
           [0009]    Thus, this invention relates to a method for isolating of phenolic substances or juvabiones from wood comprising knotwood, said method comprising the steps of 
           [0010]    a) extracting  
           [0011]    i) the over-sized chip fraction obtained by screening chipped wood, or  
           [0012]    ii) a knot-rich sub-fraction obtained from said over-sized chip fraction, or  
           [0013]    iii) knotwood obtained as residue in finishing of mechanical wood products  
           [0014]    with a polar solvent, and  
           [0015]    b) recovering the extract. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 shows a vertical cross section of a tree stem with a branch, and a vertical cross section of the branch. The figure shows further sampling of the knots and branches for studying the distribution of lignans. The dashed vertical line along the outermost layer of the bark-free stem wood is defined as zero line (0 cm).  
         [0017]    [0017]FIGS. 2A to  2 E show the distribution of total lignan in opposite wood (diamonds), side wood (filled squares) and compression wood (filled triangles) of five knot and samples and three branch samples, taken at various positions from the zero line shown in FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    The term “phenolic substances” shall be understood to cover lignans, oligolignans, flavonoids, isoflavonoids, stilbenes, tannins and phenolic acids. All these groups are mainly hydrophilic substances that can be extracted with polar, i.e. hydrophilic solvents.  
         [0019]    The term “knotwood” shall be understood to include the “knots”, i.e. the part of the branches that is embedded in the stem, and the branches extending outwards from the stem.  
         [0020]    The “over-sized chip fraction” means the rejected fraction obtained in the screening stage of the chips aimed for the pulping process. This over-sized chip fraction, which can constitute about 1 to 5% of the total amount of wood chipped, cannot be forwarded as such to the pulping process. Up to now, this fraction has been recirculated to the chipping stage or withdrawn to be burnt. This over-sized fraction comprises in addition to knotwood also considerable amounts of “normal wood”, i.e wood usable in the pulping process. The amount of knotwood in the over-sized chip fraction depends on the wood species and wood quality used, and is estimated to about 10-30%. The content of knotwood in the over-sized chip fraction is hereinafter also called “knot-rich fraction”.  
         [0021]    Although it is possible to use the over-sized chip fraction as such for extraction of phenolic substances, it may be preferable to first separate the material into a knot-rich fraction and a knot-poor fraction and to use the knot-rich fraction for extraction. The “knot-poor fraction” means the “normal wood” that can be led to the pulping process. This separation can be made directly from the over-sized chip fraction, or the material can first be refined before the screening stage.  
         [0022]    “Knotwood obtained as residue in finishing of mechanical wood products” includes, for example, the plywood sheet pieces which include knots and are cut out and replaced by corresponding pieces of normal plywood in the manufacturing stage before the individual plywood sheets are pasted together to form the finished product. Other examples are pieces of planks and boards rich in knots and therefore rejected for various reasons in building and construction, in furniture industry and the like. Also sawdust is an example of such residues. However, the useful residues are not restricted to those listed herein.  
         [0023]    The “polar solvent” is either a single polar agent, or a mixture of two or more polar agents, where said polar agent or agents have a dielectric constant that is greater than 3, determined at 25 Celsius degrees. As examples of polar solvents can be mentioned pure water only, and mixtures of water and acetone and water and alcohol, such as water and ethanol.  
         [0024]    The extraction can be carried out on dried wood or on raw wood material.  
         [0025]    Although the extraction can be physically integrated with the utilization of wood in the manufacturing of pulp or mechanical wood products, the extraction can alternatively be carried out as a separate process, because the knotwood, especially the knot-rich fraction of the over-sized chips, can easily be transported and stored for later processing.  
         [0026]    The amount of phenolic substances in knotwood varies greatly and depends on the phenolic substance in question and the wood species used. Therefore, the extract derived from the extraction stage may contain considerable concentrations of a desired phenolic compound, and may therefore, depending on the purpose, be used as such without further purification.  
         [0027]    In case further purification is needed, the methods to be used depend i.a. on the substance to be isolated and the desired degree of purity. As examples of useful purification methods can be mentioned chromatography or crystallization.  
         [0028]    As important lignans to be isolated by the method of this invention can be mentioned hydroxymatairesinol, allohydroxymatairesinol, matairesinol, conidendrin, pinoresinol, oxomatairesinol, lariciresinol, liovil, isolariciresinol, secoisolariciresinol, picearesinol, conidendric acid, and nortrachelogenin. However, the term “lignans” is not restricted to these compounds.  
         [0029]    “Oligolignans” are compounds having 3 to 6 phenylpropane units that are beta-beta linked instead of normal lignans which have two beta-beta linked phenylpropane units.  
         [0030]    As examples of flavonoids which can be isolated according to the method of this invention can be mentioned pinocembrin, dihydrokaempferol, pinobanksin, naringenin, catechin, 2,4,6-trihydroxychalcone, aromadendrin and taxifolin.  
         [0031]    As examples of stilbenes can be mentioned pinosylvin, pinosylvin monomethyl ether, dihydropinosylvin, methylpinosylvin, methyldihydropinosylvin and reservatrol.  
         [0032]    As examples of juvabiones can be mentioned epijuvabione, dehydrojuvabione, dihydroepijuvabione and epijuvabione acid.  
         [0033]    The isolation of phenolic substances or juvabiones from knotwood is very advantageous compared to the utilization of other sources. In the knot-rich fraction of the over-sized chips, the concentration of these substances is 10 to 1000 times higher than in normal wood. Many of these compounds cannot be located at all in normal wood. As a result, about 10-50% of the extract obtained according to this method may be the phenolic agent or agents. Another interesting feature is that a certain compound may be the dominating compound of the derived phenolic group of substances. For example, hydroxymatairesinol may be about 65-85% of the lignans derived from spruce knotwood.  
         [0034]    This invention thus offers a unique method for deriving the desired phenolic compound or juvabione in high concentrations in the extract. Along with this advantage, the wood material utilized for the extraction is material that hitherto has been regarded as a wood fraction useful as energy source only.  
         [0035]    The invention will be illuminated by the following non-restrictive Experimental Section  
       Experimental Section  
       [0036]    Three different studies were carried out. In a first study, three trees of Norway spruce ( Picea abies ) were investigated to reveal information on the total lignan, hydroxymatairesionol and oligolignan distribution in the knots and branches (Study 1). In a second study, seven trees of Norway spruce ( Picea abies ) were studied to reveal information on the total lignan, hydroxymatairesinol and certain other lignans and oligolignan distribution in the knots and branches (Study 2). In a third study (Study 3), the content of various lignans in three Abies species, three Picea species, two Larix species and three Pinus species were investigated. In this study, also the contents of various stilbenes and flavonoids were investigated. The methods used in Study 3 were similar to those used in Study 1 and 2. The results from Study 3 is shown in Table 5. Furthermore, samples from birch (Betula) and aspen (Populus) have also been investigated according to the method of this invention. In aspen, the flavonoids dihydrokaempferol and naringenin were found, while certain stilbenes were found in birch.  
       Study 1  
       [0037]    Material  
         [0038]    Three healthy Norway spruce trees (Table 1), grown in southern Finland, were cut in May and discs were stored at −24° C. The heartwood from several 10 knots with a dead branch (DK), still attached or fallen off, and several knots with a living branch (LK) were sampled (Table 1). Stem heartwood (HW) and sapwood (SW), with no visible compression wood, was sampled at 1.5 m height from each tree.  
                                                                                                                                                 TABLE 1                       Trees, stemwood, and knot heartwood samples analysed.                                    Growth rings at 1.5 m   Heartwood portion at 1.5 m                        Tree 1   66               Tree 2   71    {close oversize brace}    40-45%       Tree 3   64                    Stem   Knot with dead branch   Knot with living branch                    Tree 1            HW 1.5*   DK 3.5       LK 4.5   LK 13.5       SW 1.5   DK 5.5       LK 9-a   LK 15-a                   LK 12   LK 15-b            Tree 2            HW 1.5   DK 4.5   DK 13.5   LK 8           SW 1.5   DK 6.5       LK 9           DK 7.5       LK 14.5            Tree 3            HW 1.5   DK 6   DK 11-b   LK 7   LK 17.5       SW 1.5   DK 8   DK 13.5   LK 12           DK 11-a       LK 15                          
 
         [0039]    The heartwood of five additional knots and three branches were split into 1 cm thick sections and further divided into opposite, side, and compression wood, for examining the distribution of lignans (FIG. 1).  
         [0040]    Methods  
         [0041]    The wood samples were splintered, freeze-dried and ground in a Wiley mill, producing particles passing a 10-mesh screen. A second freeze-drying step after the milling ensured almost complete removal of volatile compounds. The wood samples for the lignan distribution study were freeze-dried, splintered using a scalpel, and freeze-dried again.  
         [0042]    Sequential extraction was carried out in an ASE-apparatus (Accelerated Solvent Extractor). The lipophilic extractives were first extracted with hexane (solvent temperature 90° C., pressure 13.8 MPa, 2×5 min static cycles) and then the hydrophilic extractives were extracted with an acetone:water (95:5 v/v) mixture (solvent temperature 100° C., pressure 13.8 MPa, 2×5 min static cycles). The samples for the lignan distribution study were extracted only with an acetone:water (95:5 v/v) mixture (as above, 3×5 min static cycles).  
         [0043]    Lignans, free fatty acids, resin acids and free sterols were, after evaporation of the extract solutions and silylation of the extractives, analysed on a 25 m×0.20 mm i.d. crosslinked methyl polysiloxane column (HP-1). Heneicosanic acid and betulinol were used as internal standards. A correction factor of 1.2 for betulinol was used for the quantification of the lignans. All results given as mg/g or % (w/w) are calculated on a freeze-dried wood basis.  
         [0044]    Oligolignans, in the same silylated samples as above, were analysed according to (6) using cholesteryl heptadecanoate as internal standard.  
         [0045]    Identification of individual components was done by GC-MS analyses of the silylated components with an HP 6890-5973 GC-MSD instrument, using a similar GC column as above.  
         [0046]    Results  
         [0047]    The lignans and oligolignans were the main components of the hydrophilic extractives in all samples (Table 2). Small amounts (&lt;1.1 mg/g) of monomeric sugars were also found in most samples. Trace amounts (&lt;0.2 mg/g) of simple phenols, dominated by coniferyl alcohol and vanillic acid, were also present in all samples.  
         [0048]    The amount of lignans was extremely high in the knots, between 6 and 16% (w/w), compared to the maximum of 0.2% in the stemwood (Table 2). The variation in the total amount of lignans was large among the knots of a single tree and also between the different trees. There seemed to be no difference between knots with a living and a dead branch. The identified lignans were the same as found earlier in Norway spruce (7). Ten unidentified lignans were also detected and quantified. The sum of the two isomers of hydroxymatairesinol (HMR) dominated all samples.  
         [0049]    Two groups of a complex mixture of oligomeric phenolic substances were detected and quantified by GC (Table 2). Preliminary size-exclusion fractionation and MS studies showed these compounds to be composed of phenylpropane units similar to those of lignans. The SEC and GC retention times suggested that these compounds were oligomeric (trimeric and tetrameric) lignans, here called oligolignans. The total amount of oligolignans ranged between 2 and 4% (w/w) in the knots. The amount of oligolignans was about 20-30% of the amount of lignans in all knots.  
                                                                                                                                                           TABLE 2                           The amount of lignans and oligolignans in the stemwood       and knot heartwood samples. HMR was the most abundant lignan in       all samples.                Lignans       Oligolignans                    Total   HMR   Trimers   Tetramers           mg/g   % of total   mg/g   mg/g                        Tree 1                HW 1.5   1.1   44   0.26   0.18           SW 1.5   0.7   53   0.17   0.08           DK 3.5   118   66   17   13           DK 5.5   123   68   17   10           LK 4.5   119   68   22   10           LK 9-a   124   69   21   9           LK 12   159   73   26   12           LK 13.5   120   73   20   10           LK 15-a   156   77   24   15           LK 15-b   149   80   25   14            Tree 2                HW 1.5   0.5   17   0.11   0.05           SW 1.5   0.2   25   0.07   0.03           DK 4.5   90   76   11   11           DK 6.5   134   75   16   14           DK 7.5   144   73   18   14           DK 13.5   117   76   15   11           LK 8   142   74   18   10           LK 9   129   75   17   10           LK 14.5   154   77   21   9            Tree 3                HW 1.5   2.2   37   0.32   0.13           SW 1.5   0.2   25   0.06   0.02           DK 6   63   72   8   10           DK 8   75   74   10   13           DK 11-a   124   76   17   14           DK 11-b   77   76   11   10           DK 13.5   114   81   14   13           LK 7   95   77   12   13           LK 12   145   82   16   9           LK 15   104   77   17   8           LK 17.5   134   76   25   14                      
 
         [0050]    [0050]FIGS. 2A to  2 E show the distribution of lignans from near the base of the knot to 10-20 cm out in the branch. The lignans were almost absent 20 cm out in the branches from Tree 2 and 3, while they had decreased strongly in the branch from Tree 1. The amount of lignans in a radial direction, from the pith into the outer branch, was quite even inside the stem. The concentration of lignans decreased in the order opposite wood-side wood-compression wood. However, since knots usually contain smaller amounts of opposite wood than side wood and compression wood, the highest amount of lignans is situated in side wood and compression wood.  
       Study 2  
       [0051]    In this study, results are reported from analysis of the hydrophilic and lipophilic extractives of knots from seven Norway spruce trees. The objective was to determine the amount and composition, as well as the variability within a tree and between trees, of the extractives in knotwood and stemwood. We were also interested in differences due to geographical location, why two of the seven trees were sampled from northern Finland.  
         [0052]    Material  
         [0053]    Seven healthy Norway spruce trees (Table 3) were felled, and samples of stemwood and knots were sawn and put into storage at −24° C. within 6 h. Trees 1-3 were felled in May, trees 4-5 in January, and trees 6-7 in October. Trees 1-3 and 6-7 were densely grown in sandy soil, while trees 4-5 were planted on former arable land. Trees 1-5 had an average diameter of about 30 cm at 1.5 m height, while the diameters of trees 6-7 were about 25 cm. Trees 4-5 had grown fast. The heartwood from knots at a dead branch (DK), still attached or fallen off, and knots at a living branch (LK) were sampled. For short, the expression knots means knot heartwood. Stem heartwood (HW) from trees 1-3 and 6-7 and stem sapwood (SW) from trees 1-7, with no visible reaction or decayed wood, was sampled at 1.5 m height. The number in each sample code (e.g. DK 3.5) expresses the height in meters above ground while the suffix a or b expresses different knots at the same height. The heartwood of seven additional knots and five branches were split into 1 cm thick discs and further divided into opposite, side, and compression wood, for examining the distribution of lignans (FIG. 1).  
                                                     TABLE 3                                   Growth place   Growth rings   Heartwood proportion, area-%           (DK; LK)*   at 1.5 m   of cross section at 1.5 m                                    Tree 1   Southern Finland   66                   (2; 6)       Tree 2   Southern Finland   71           (4; 3)        {close oversize brace}     40-45       Tree 3   Southern Finland   64           (5; 4)       Tree 4   Southern Finland   17           (—; 2)       Tree 5   Southern Finland   17    {close oversize brace}     0           (—; 2)       Tree 6   Northern Finland   150           (2; 1)       Tree 7   Northern Finland   134    {close oversize brace}     60-65           (2; 2)                          
 
         [0054]    The methods for isolation and analysis of the isolated substances were 15 essentially those described in Study 1 above.  
         [0055]    Results  
         [0056]    The lignans and oligolignans were the main components of the hydrophilic extractives (Table 4). In addition, mainly small amounts of monomeric sugars, simple phenols (or monolignols), and dimeric non-lignan aromatic compounds of dilignoltype, such as 1,3-(bis-guaiacyl)-1,2-propandiol, were detected in most samples. The amount of lignans was exceptionally large in the knots compared to the stemwood (Table 4). The knots of the trees from northern Finland contained 14-24% (w w −1 ), while the knots from southern Finland contained 6-16% (w w −1 ) of lignans. Even the knots from the young trees contained 4-8% (w w −1 ) lignans. Lignans were found in small amounts also in the sapwood.  
         [0057]    The variation in the content of lignans was large between the knots of a single tree and also between knots from different trees. The largest amounts of lignans were found in living knots in all trees. It is not possible to draw any conclusions whether the larger amounts of lignans in the knots from the northern trees are due to higher age or place of growth, since the trees from different location were of different age. The tree genotype was however different depending on the geographical location. The branches of the northern trees have a smaller angle between the stem and the downside of the branch. This is typical for Norway spruce trees grown north of the pole circle. This, and the fact that the climate is harder, would certainly cause another type of stress on the knots than for trees from southern Finland. It has been suggested earlier that external stress, causing eccentric growth of Norway spruce stems, is associated with higher lignan concentrations (2).  
         [0058]    The main identified lignans were mainly the same as found earlier in Norway spruce (7). The identified lignans were two epimers of hydroxymatairesinol (HMR), α-conidendrin, liovil (two isomers), secoisolariciresinol, lariciresinol, pinoresinol, matairesinol, isolariciresinol, α-conidendric acid and a lignan called lignan A. Seven unknown minor lignans were also detected and quantified. The two epimers of HMR dominated in all knots (Table 4). The epimers are here called HMR 1 and HMR 2 based on their elution order on GC. The structure of the major lignan, HMR 2, and its minor epimer, HMR 1 or allo-HMR, has been discussed in the literature (8, 9). The ratio HMR 2/HMR 1 was between 2 and 4 in trees 1-2 and 6-7, while the range was 2-7 in tree 3, 4-5 in tree 4, and 1-3 in tree 5. HMR was the dominating lignan also in the stem sapwood and heartwood samples, even though the contribution of the other lignans was higher. The ratio HMR 2/HMR 1 was between 2 and 5 in heartwood and even up to 11 in sapwood. In the knots from tree 6 and 7 we found a lignan that has not been identified earlier in spruce trees, in amounts ranging from 2 to 7 mg g −1 . The mass spectrum and the GC retention time were the same as for the lignan (−)-nortrachelogenin (NTG) which was recently identified in knot heartwood of  Pinus sylvestris  (10). However, the NTG-enantiomer (+)-wikstromol will have the same mass spectrum and retention time. Since it was not possible to obtain the lignan in enough pure form for determining the optical rotation, it remains unclear, which of the enantiomers occurs in Norway spruce. Also an earlier name, pinopalustrin, has been suggested for NTG (11, 12).  
         [0059]    The volume of the pith was quite large compared to the total knot volume in most knots. Even though the dry mass of the pith is small compared to the total knot mass, it was of interest to analyse the extractives in the pith. The pith material contained mainly lignans, about 120 mg g −1 , with HMR as the most abundant lignan. Small amounts of an NTG-isomer, with the same mass spectrum but different GC retention time, was also identified in the pith material.  
                                                                                                                                                                                                                                                                                                                                                                                                           TABLE 4                                       Lignans   Oligolignans                Total amount   HMR*   Coni*   Liovil   Seco*   Other   Total amount**   Trimers                mg/g   % of total lignans   mg/g   %                        Tree 1, southern Finland, 66 years            HW 1.5   0.9   52   6   9   5   28   0.4   59       SW 1.5   0.6   57   3   16   5   20   0.3   67       DK 3.5   115   68   6   5   10   11   30   58       DK 5.5   120   70   4   6   9   12   27   61       LK 4.5   116   70   9   4   4   13   32   69       LK 9-a   120   71   5   5   7   12   29   71       LK 12   159   73   3   5   6   12   38   68       LK 13.5   117   75   4   5   4   12   30   68       LK 15-a   152   80   3   3   3   12   38   62       LK 15-b   149   79   4   3   3   11   39   64            Tree 2, southern Finland, 71 years            HW 1.5   0.3   28   4   12   3   54   0.1   70       SW 1.5   0.1   37   3   10   7   44   0.2   69       DK 4.5   88   78   7   4   2   10   22   51       DK 6.5   131   76   5   4   4   11   30   54       DK 7.5   141   75   5   4   6   11   32   55       DK 13.5   114   78   4   3   4   11   26   57       LK 8   139   76   5   3   5   11   29   64       LK 9   126   76   4   3   5   11   26   63       LK 14.5   151   79   3   5   2   11   30   69            Tree 3, southern Finland, 64 years            HW 1.5   1.9   43   2   20   9   25   0.1   72       SW 1.5   0.1   33   3   19   8   37   0.4   71       DK 6   61   75   8   6   3   9   18   45       DK 8   71   78   6   7   1   8   23   43       DK 11-a   119   79   4   7   1   8   31   56       DK 11-b   74   79   5   6   1   8   20   52       DK 13.5   111   84   4   3   1   8   27   51       LK 7   92   80   7   4   2   8   25   48       LK 12   141   85   4   3   1   8   25   65       LK 15   101   79   2   9   1   9   25   67       LK 17.5   131   78   1   10   1   10   39   64            Tree 4, southern Finland, 17 years            SW 1.5   0.3   38   &lt;1   25   8   28   0.4   56       LK 3.5   47   72   1   8   11   9   19   63       LK 5.5   35   73   1   8   10   8   16   62            Tree 5, southern Finland, 17 years            SW 1.5   0.6   53   6   19   6   16   0.4   59       LK 4   77   66   &lt;1   6   20   9   23   62       LK 6   39   80   &lt;1   6   8   6   23   61            Tree 6, northern Finland, 150 years            HW 1.5   2.5   51   11   8   9   21   0.2   69       SW 1.5   0.2   28   &lt;1   17   25   30   0.9   66       DK 2.5   139   71   9   3   6   10   31   42       DK 3   138   71   10   3   5   11   34   42       LK 9   171   77   8   3   2   10   33   45            Tree 7, northern Finland, 134 years            HW 1.5   1.2   44   7   13   9   26   0.4   60       SW 1.5   0.6   28   1   26   19   25   0.9   59       DK 4   171   73   6   5   4   13   43   46       DK 5   172   73   6   4   5   12   48   43       LK 6   209   74   6   5   4   12   56   49       LK 8   244   72   6   5   3   14   44   49                                  
 
         [0060]    Table 5 shows the results from Study 3.  
                                                                                                                       TABLE 5                       Hydrophilic extractives, % of dry knot wood                                      Abies       Larix                    alba       balsamea       sibirica       sibirica       lariciana                 Lignans:       Isolariciresinol   0.6   0.3       Secoisolariciresinol   3.9   4.1   3.0   1.4   1.3       Lariciresinol   0.8   2.1   0.8   0.3   0.1       Flavonoids:       3,5,7,4′,x-               0.3   0.5       pentahydroxy       flavanone                          Picea                  Lignans:     abies       glauca       sitchensis                         Secoisolariciresinol   0.6   0.3               Liovil           0.2           HMR(1)   2.1   0.8           HMR(2)   6.0   4.3                              Pinus                        contorta       sibirica       sylvestris                         Lignans:           Isolariciresinol       0.4           Secoisolariciresinol       0.3   0.02           Liovil   0.04           lariciresinol       2.6           NTG   0.1       1.7           Stilbenes:           Pinosylvin-Me   0.1   2.4   1.0           Pinosylvin   0.2   0.9   1.1           Dihydropinosylvin-Me       1.4           Dihydropinosylvin       0.2           Flavonoids:           Pinocembrin   0.2   0.5           Pinobanksin   0.1   0.2           Dihydrokaempferol   0.05   0.02                      
 
         [0061]    Additional wood species were investigated according to the methods described above and the following results were obtained:  
         [0062]    [0062] Abies concolor  (secoisolariciresinol 2.5%, HMR 2 1.1%)  
         [0063]    [0063] Abies lasiocarpa  (epijuvabione 1.1%, dehydrojuvabione 0.8%)  
         [0064]    [0064] Picea mariana  (HMR 2 3.5%)  
         [0065]    [0065] Pseudotsuga menziesii  (dihydroepijuvabione 0.7%, isolariciresinol 6.3%, secoisolariciresinol 2.0%, lariciresinol 1.5%)  
         [0066]    [0066] Pinus banksiana  (epijuvabione acid 1.2%, pinosylvin monomethyl ether 1.1%, nortrachelogenin 1.3%)  
         [0067]    [0067] Pinus resinosa  (pinosylvin 1.4%, pinosylvin monomethyl ether 2.8%, matairesinol 1.2%)  
         [0068]    [0068] Larix decidua  (dihydrokaempferol 1.1%, taxifolin 2.8%, isolariciresinol 1.1%, secoisolariciresinol 4.8%, lariciresinol 1.3%)  
         [0069]    [0069] Betula pendula, Betula verrucosa, Alnus incana  (several stilbene glycosides 1-2%)  
         [0070]    It will be appreciated that the methods of the present invention can be incorporated in the form of a variety of embodiments, only a few of which are disclosed herein. It will be apparent for the expert skilled in the field that other embodiments exist and do not depart from the spirit of the invention. Thus, the described embodiments are illustrative and should not be construed as restrictive.  
       References  
       [0071]    1. Freudenberg K and Knof L, “Lignanes des Fichtenholzes”. Chem. Ber. 90, 2857-69, 1957.  
         [0072]    2. R. Ekman, “Distribution of lignans in Norway spruce”, Acta Acad. Abo, Ser. B, 39:3, 1-6 (1979).  
         [0073]    3. S. Nishibe, “Bioactive phenolic compounds for cancer prevention from herbal medicines”, In Food Factors for Cancer Prevention, Ed. by H. Ohigashi, T. Osawa, J. Terao, S. Watanabe and T. Yoshikawa, Springer-Verlag, Tokyo, 276-279 (1997).  
         [0074]    4. J. D. Ford, L. B. Davin and N. G. Lewis, “Plant lignans and health: Cancer chemoprevention and biotechnological opportunities”, In Plant Polyphenols 2: Chemistry, Biology, Pharmacology, Ecology, Ed. by G. G. Gross, R. W. Hemingway and T. Yoshida, Kluwer Academic/Plenum Publishers, New York, 675-694 (1999).  
         [0075]    5. N. M. Saarinen, A. Wärri, S.I. Makelä, C. Eckerman, M. Reunanen, M. Ahotupa, S. M. Salmi, A. A. Franke, L. Kangas and R. Santti, “Hydroxymatairesinol, a novel enterolactone precursor with antitumor properties from coniferous tree ( Picea abies )”, Nutr. Cancer 36, 207-216 (2000).  
         [0076]    6. F. Örså and B. Holmbom, “A convenient method for the determination of wood extractives in papermaking process waters and effluents”, J. Pulp Pap. Sci. vol 20:12, J361-J366 (1994).  
         [0077]    7. R. Ekman, “Analysis of lignans in Norway spruce by combined gas chromatography—mass spectrometry”, Holzforschung 30, 79-85 (1976).  
         [0078]    8. Kawamura F., H. Ohashi, S. Kawai, F. Teratani and Y. Kai. 1996. Photodiscoloration of Western hemlock ( Tsuga heterophylla ) sapwood II. Structures of constituents causing photodiscoloration. Mokuzai Gakkaishi. 42, 301-307.  
         [0079]    9. Mattinen J., R. Sjöholm and R. Ekman. 1998. NMR-spectroscopic study of hydroxymatairesinol, the major lignan in Norway spruce ( Picea abies ) heartwood. ACH—Models Chem. 135, 583-590.  
         [0080]    10. Ekman R., S. Willför, R. Sjöholm, M. Reunanen, J. Mäki, R. Lehtilä and C. Eckerman. 2001. Identification of the lignan nortrachelogenin in knot and branch heartwood of Scots pine ( Pinus sylvestris  L.). Holzforschung, in press.  
         [0081]    11. Carnmalm B. 1959. Pinopalustrin, en ny lignan. In: Resumeer av sektionsföredrag. Svensk Kem. Tidskr. 71, 440.  
         [0082]    12. Carnmalm B., H. G. H. Erdtman, G. C. Harris and T. F. Sanderson. 1977. The structure of pinopalustrin and its relations to other lignans. Acta Chem. Scand. B31, 433.