Lignans, wood

Okunishi, T., Umezawa, T. and Shimada, M. (2000) Enantiomeric compositions and biosynthesis of Wikstroemia sikokiana lignans. /. Wood Sci., 46, 234-A2. 

A major drawback of this study was that we measured lipid peroxidation ex vivo, but not in vivo using the latest and most promising methods such as F2 isoprostanes (Roberts and Morrow, 2000). However, we are planning to do that soon, so hopefully future studies will bring us more detailed information about the effects of phloem on lipid peroxidation. In conclusion, our study showed that lignans are bioavailable from the wood matrix, that long-term consumption of phloem is safe and that ingestion of phloem can inhibit lipid peroxidation in humans. 

In the meantime, all of the higher intermediates shown in Fig. 2 have been tested and numerous comprehensive surveys of this work have appeared (24, 81—83, 91, 93, 112, 113, 132). Some of these simultaneously describe the formation of secondary aromatic substances in wood, i.e. lignans, tannins, flavonoids, etc., which arise by essentially similar routes coupled with acetate metabolism. A few outstanding recent developments may bear repetition here. 

Umezawa T (2010) The cinnamate/monohgnol pathway. Phytochem Rev 9 1-17 Umezawa T (1997) Lignans. In Higuchi T (ed) Springer series in wood science, biochemistry and molecular biology of wood. Springer, Berlin, pp. 181-194... 

Suzuki S, Umezawa T (2007) Biosynthesis of lignans and norUgnans. J Wood Sci 53 273-284... 

Okunishi T, Umezawa T, Shimada M (2001) Isolation and enzymatic fomiation of lignans of Daphne genkwa and Daphne odora. J Wood Sci 47 383-388... 

Umezawa T, Davin LB, Lewis NG (1991) Formation of lignans (-)-secoisolariciresinol and (-)-matairesinol with Forsythia intermedia ceU-free extracts. J Biol Chem 266 10210-10217 Okunishi T, Sakakibara N, Suzuki S et al (2004) Stereochemistry of matairesinol formation by Daphne secoisolariciresinol dehydrogenase. J Wood Sci 50 77-81 XiaZ-Q, Costa MA, Pelissier HC et al (2001) Secoisolariciresinol dehydrogenase purification, cloning, and functional expression. J Biol Chem 276 12614-12623... 

Shen, Y., Kojima, Y., and Terazawa, M., Two lignan rhamnosides from birch leaves, Journal of Wood Science, 45, 326, 1999. 

Ullmann reaction (4, 33-34). Semmelhack et al.1 recorded details of the coupling of aryl and vinyl halides with Ni(0) complexes, (COD)2Ni or Ni[P(C6H5)3]4. This reaction was used for the first synthesis of almusone (3), an antileukemic lignan obtained from the wood of Alnus japonica Steud. In the case of ort/io-substituted aryl iodides such as 1, reduction becomes a competing reaction and the yields are only moderate. In fact o,o-disubstituted aryl halides cannot be coupled under these conditions. Deliberate addition of a proton source increases formation of the reduction product. Acetic or trifluoroacetic acid are useful for this purpose. Added triphenyl-phosphine also promotes reduction. 

Adlercreutz H, Fotsis T, Heikkinen R, Dwyer JT, Woods M, Goldin BR, Gorbach SL. 1982. Excretion of the lignans enterolactone and enterodiol and of equol in omnivorous and vegetarian postmenopausal women and in women with breast cancer. Lancet 2 1295-1299. 

Table 1 lists crude extracts (mother liquor) of the plants studied however, the lignans were generally isolated after re-extractions rather than directly from the crude extracts. Extraction and isolation details are provided in the references [68-88] given in Table 1. As seen from the table, crude extracts were prepared with a polar solvent, mostly ethanol, sometimes water, but higher diversity was obtained by working with a direct acetone extract of T. maireii twigs, considering the number of the lignans isolated. An early study of Taxus lignans by Erdtman and Tsuno reported a brief comparative examination of several Taxus woods [67].

Lignans were found in the Taxus extracts prepared from bark, heart-wood, needles, roots, or other parts. In the studies on European yew T. bac-cata L. carried out by Das et al., the extracts were prepared by extracting from the needles rather than the heartwood of the plant using a solvent system CL Ck-MeOH (1 1) [70-73], although in the studies on Turkish T. baccata, the extracts were prepared by applying EtOH to the needles and twigs of the plant [74-76]. So far, after many studies of T. baccata... 

The biosynthesis of extractives is controlled genetically and hence each wood species tends to produce specific substances. As a result of secondary changes, heartwood contains a large variety of phenolic substances. From the chemotaxonomical point of view, chemical structures of various flavonoids, lignans, stilbenes, and tropolones are of interest. For example, species within genera such as Pinus, Acacia, and Eucalyptus can be classified according to their characteristic composition of phenolic substances. 

Ozawa S, Sasaya T (1988) Extractives of Todomatsu Abies sachalinensis masters V A novel dibenzylbutyrolactol lignan from the wood of Abies sachalinensis Mokuzai Gakkaishi 34 851-857... 

Suzuki, S. (2002) Stereochemical diversity in lignan biosynthesis and establishment of norlignan biosynthetic pathway. Wood Res., 89, 52-60. 

---