Science in Society Archive

Knotty but Nice: Spectacular Anti-Cancer Agents in Tree Knots

Prof. Joe Cummins reports on further anti-cancer chemicals that are found in common plant sources

Two years ago I wrote on how organic agriculture has the potential to combat cancer. Plant chemicals called phenolics or flavonoids, effective in preventing cancer, have been found elevated in organic foods [1]. Another family of plant chemicals related to flavonoids, called lignans, recently yielded spectacular results in preventing and treating human cancers.

Lignans contain two benzene rings to which are attached particular three carbon arms. Lignans are not to be confused with lignin, the polymer that binds cellulose fibers together to make cell walls. Lignin is synthesized from monomer units similar to lignans, but lignin is not associated with the beneficial properties of lignans.

A recent review suggested that an anti-cancer diet would decrease breast, colorectal and prostate cancer by 60 to 70 percent and lung cancer by 40 to 50 percent. Taking flaxseed, especially its lignan fraction, lowers cancer risk [2]. Flaxseed lignan has been found effective not only in treating cancer but also in reducing the risk of heart disease and to have beneficial effects in lupus and polycystic kidney disease [3]. Flaxseed meal ameliorated kidney damage in type-two diabetes [4]. The anticancer effect of a plant lignan was demonstrated using human prostate cancer cells transplants in nude (immune deficient) mice [5]. Rat mammary tumors were reduced after treatment with a plant lignan isolated from the knots of spruce trees [6]. Along with flaxseed extracts the knots of trees are proving to be a rich source of anti-cancer lignans.

The knots of spruce and fir trees are believed to be the richest source of lignans. Up to 24 percent of the dry weight of the knot may be lignans [7, 8], while much lower levels are found in the stem wood [9]. Extracting lignans from the knots was not difficult.

Knot-wood extracts proved to be effective in controlling paper-mill bacteria that undermine paper quality [10]; and lignans were a deterrent to feeding insects [11]. These anti-microbial and insecticidal properties will no doubt be further developed.

Not surprisingly, there has been a spate of patenting to exploit the therapeutic potential of lignans. Of the many relevant patents, US Patent 6451849 deals with the use of a lignan for cancer prevention, and for treating non-cancer hormone-dependent disease and cardiovascular disease. The patent describes an active lignan and its preparation [12]. US patent 67675654 describes a method for preparing plant lignan for use in treating cancer, diabetes, lupus, hypertension and high blood pressure [13]. The first patent applications for genetically modified crops with increased lignan content have begun to appear. US patent application 20020174452 is for genetic modification of monocots such as rice with genes that increase lignan level in grain using tissue specific promoters [14].

It is not surprising that biotechnology has taken lignan to heart, and that industry has a large and shameless public relations machinery which will likely try to make it look as if biotechnology, and not nature, that has invented lignans.

Like numerous other health-promoting natural chemicals, lignans are common in plant species that are still widely available, although they are increasingly threatened by industrial farming and especially GM crops, which have now proved to be even more destructive of natural biodiversity than conventional industrial farming ("GM crop fails final test", ISIS report). This is another reason for a comprehensive shift to sustainable farming systems that preserve and enhance natural biodiversity.

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Article first published 29/04/05


  1. Cummins J. Organic agriculture helps fight cancer. ISIS Report 2003
  2. Donaldson M. Nutrition and cancer: A review of the evidence for an anti-cancer diet. Nutr. J. 2004, 3,19-40.
  3. Westcott N. and Muir A. Flax seed lignan in disease prevention and health promotion Phytochemistry Reviews 2003, 2, 401-17.
  4. Velasquez M, Bhathena S, Ranich T, Schwartz A, Kardon D, Ali A, Haudenschild C. and Hansen C. Dietary flaxseed meal reduces proteinuria and ameliorates nephropathy in an animal model of type II diabetes mellitus. Kidney Int. 2003, 64, 2100-7.
  5. Bylund A, Saarinen N, Zhang JX, Bergh A, Widmark A, Johansson A, Lundin E, Adlercreutz H, Hallmans G, Stattin P. and Makela, S. Anticancer effects of a plant lignan 7-hydroxymatairesinol on a prostate cancer model in vivo. Exp Biol Med (Maywood). 2005, 230, 217-23.
  6. Kangas L, Saarinen N, Mutanen M, Ahotupa M, Hirsinummi R, Unkila M, Perala M, Soininen P, Laatikainen R, Korte H. and Santti, R Antioxidant and antitumor effects of hydroxymatairesinol (HM-3000, HMR), a lignan isolated from the knots of spruce. Eur J Cancer Prev. 2002 ,11 Suppl 2, S48-57. .
  7. Holmbom B, Eckerman C, Eklund P, Hemming J, Nisula L, Reunanen M, Sjöhol R, Sundberg A, Sundberg K and Willför S. Knots in trees-A new rich source of lignan. Phytochemistry Reviews 2003, 2, 331-40.
  8. Willfor S, Ahotupa M, Hemming J, Reunanen M, Eklund P, Sjoholm R, Eckerman C, Pohjamo S. and Holmbom B. Antioxidant activity of knotwood extractives and phenolic compounds of selected tree species. J Agric Food Chem. 2003 17, 51, 7600-6.
  9. Willför S, Hemming J, Reunanen M, Eckerman C and Holmbom B. Lignans and lipophilic extractives in Norway spruce knots and stemwood. Holzforschung 57, 2003, 27–36.
  10. Lindberg L, Willfor S and Holmbom B. Antibacterial effects of knotwood extractives on paper mill bacteria. J Ind Microbiol Biotechnol. 2004, 31,137-47.
  11. Harmatha J and Nawrot J. Insect feeding deterrent activity of lignans and related phenylpropanoids with a methylenedioxyphenyl (piperonyl) structure moiety Entomologia Experimentalis et Applicata 2002, 104, 51–60.
  12. Ahotupa M,.Eckerman C, Kangas L, Makela S, Saarinen N, Santti R and Warri A. Use of Hydroxyymatairesinol for Prevention of Cancers, Non-canecer, Hormone Dependent Diseases and Cardiovascular Diseases by Hydroxyymatairesinol, and A Pharmaceutical Preparation, Food Additive and Food Product Comprising Hydroxyymatairesinol 2002 US Patent 6 451 849.
  13. Shukla R, Hilaly A and Moore K. Process for obtaining lignan 2004 US Patent 6 767 565.
  14. Lewis N, Davin L and Huang N. Monocot seeds with increased lignan content. 2002 US Patent application 20020174452

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