Skip to main content

Official Journal of the Japan Wood Research Society

Journal of Wood Science Cover Image

Photodiscoloration of western hemlock (Tsuga heterophylla) sapwood III Early stage of photodiscoloration reaction with lignans


The reaction during the early stage of photodiscoloration of constituents in western hemlock [Tsuga heterophylla (Raf. Sarg., Pinaceae] sapwood was investigated with chemical methods. The main photodiscoloring constituents, hydroxymatairesinol, allohydroxymatairesinol, α-conidendrin, and oxomatairesinol, were used as substrates for light-irradiation experiments in vitro. The structures of photodiscoloration reaction products were elucidated by isolation and instrumental analyses and/or co-high-performance liquid chromatography analyses with authentic specimens. The experiment was undertaken to distinguish each series of liquid phases using chloroform, water (both including a trace of methanol), and methanol, and the solid phase. The reaction products allohydroxymatairesi (2), oxomatairesinol (3), α-conidendrin (4), allo-7′-methoxymatairesinol (5), 7′-methoxymatairesinol (6), and vanillin (7) were isolated or detected in the reaction mixture of a hydroxymatairesinol system. The reaction products hydroxymatairesinol (1), 3, 4, 5, 6, and 7 were confirmed in the reaction system of allohydroxymatairesinol, which was an epimer of hydroxymatairesinol. Product 3 was confirmed from the α-conidendrin system, and reaction product 7 was confirmed from oxomatairesinol. The photodiscoloration reaction of western hemlock sapwood could be initiated by the formation of phenoxy radicals from the respective constituents. The reaction was then presumed to progress via formation of a quinonemethide intermediate in many of them. It was suggested that the reactive species, such as phenoxy radical or quinonemethide intermediate, formed by lightirradiation might be converted to quinone derivatives and colored oligomers. Products 1, 2, 3, 4, and 7, formed from substrates such as hydroxymatairesinol, allohydroxymatairesinol, α-conidendrin, and oxomatairesinol, were the same as the original metabolic constituents of western hemlock. Therefore it was concluded that the photodiscoloration of western hemlock depends not on the quantitative level of a few respective metabolites but, rather, on the coexistence of many metabolites.


  1. 1.

    Barton GM (1968) Significance of western hemlock phenolic extractives in pulping and lumber. Forest Prod J 18(5):76–80

    CAS  Google Scholar 

  2. 2.

    Yoshimoto T (1983) Wood color and its discoloration. In: Imamura H, Okamoto H, Gotoh T, Yasue M, Yokota T, Yoshimoto T (eds) Chemistry of wood utilization (in Japanese). Kyoritu, Tokyo pp 204–214

    Google Scholar 

  3. 3.

    Kai Y (1985) Extractives in utilization of wood. In: Harada T, Saeki H, Fushitani M, Okano K, Haraguchi T, Moroboshi N (eds) Wood chemistry (in Japanese). Buneido, Tokyo pp 177–185

    Google Scholar 

  4. 4.

    Yoshimoto T, Samejima M (1977) Rengas wood extractives relating to light induced reddening (in Japanese). Mokuzai Gakkaishi 23:601–604

    CAS  Google Scholar 

  5. 5.

    Drews SE, Roux DG (1964) Condensed tannins. 20. Chromophoric properties of flavan-4-ols, flavan-3,4-diols and condensed tannins. Biochem J 92:559–564

    Article  Google Scholar 

  6. 6.

    Morgan JWW, Orsler RJ (1968) The chemistry of colour changes in wood. 1. The significance of stilbenes. Holzforschung 22:11–16

    CAS  Article  Google Scholar 

  7. 7.

    Laver ML, Arvey SW (1996) Chemical brown staining of douglas fir wood: light and oxygen susceptibility of extractives. Forest Prod J 46(7/8):96–101

    CAS  Google Scholar 

  8. 8.

    Waiss AC, Lundin RE, Lee A, Corse J (1967) Photochemistry of quercetin pentamethyl ether. J Am Chem Soc 89:6213–6218

    CAS  Article  Google Scholar 

  9. 9.

    Evans RS, Halvorson FIN (1962) Cause and control of brown stain in western hemlock. Forest Prod J 12(8):367–373

    CAS  Google Scholar 

  10. 10.

    Kawamura F, Ohashi H, Kawai S, Teratani F, Kai Y (1996) Photodiscoloration of western hemlock (Tsuga heterophylla) sapwood. I. Actual conditions upon photodiscoloration of woody parts. Mokuzai Gakkaishi 42:293–300

    Google Scholar 

  11. 11.

    Kawamura F, Ohashi H, Kawai S, Teratani F, Kai Y (1996) Photodiscoloration of western hemlock (Tsuga heterophylla) sapwood. 11. Structures of constituents causing photodiscoloration. Mokuzai Gakkaishi 42:301–307

    CAS  Google Scholar 

  12. 12.

    Kawamura F, Kawai S, Ohashi H (1997) Sesquilignans and lignans from Tsuga heterophylla. Phytochemistry 44:1351–1357

    CAS  Article  Google Scholar 

  13. 13.

    Barton GM (1978) Significance of western hemlock phenolic extractives in groundwood pulping. Tappi 56(5):115–118

    Google Scholar 

  14. 14.

    Hrutfiord BF, Luthi R, Hanover KF (1985) Color formation in western hemlock. J Wood Chem Technol 5:454–460

    Article  Google Scholar 

  15. 15.

    Goldschmid O, Hergert HL (1961) Examination of western hemlock for lignin precursors. Tappi 44:858–870

    CAS  Google Scholar 

  16. 16.

    Kringstad K, Lin SY (1970) Mechanism in the yellowing of high-yield pulps by light: structure and reactivity of free radical intermediates in the photodegradation of lignin. Tappi 53:2296–2301

    CAS  Google Scholar 

  17. 17.

    Brunow G, Sivonen M (1975) The yellowing of lignin. Part 11. The participation of oxygen in the photo-dehydrogenation of lignin model compounds. Paperi ja puu 25:215–220

    Google Scholar 

  18. 18.

    Thomas MJ, Foote CS (1978) Chemistry of singlet oxygen. XXXVI. Photooxygenation of phenols. Photochem Photobiol 27:683–693

    CAS  Article  Google Scholar 

  19. 19.

    Harada K, Hidaka J (1978) Optically active substance I. In: Ohki M (ed) Stereochemistry (in Japanese). Dai Nippon Tosho, Tokyo pp 65–100

    Google Scholar 

  20. 20.

    Lorene LB, Pavlovie VD, Krstic NM, Mihalovic MLJ (1993) Synthesis, structure, and reactivity of secosteroids containing a medium-size ring. Helv Chim Acta 76:2254–2262

    Article  Google Scholar 

  21. 21.

    Tanahashi M (1989) Degradation mechanisms of wood components by steam explosion. PhD thesis, Kyoto University, pp 60–65

  22. 22.

    Matsuura T, Matsushima H, Nakashima R (1970) Photoinduced reactions. XXXVI. Photosensitized oxygenation of 3-hydroxyflavones as a nonenzymatic model for quercetinase. Tetrahedron 26:435–443

    CAS  Article  Google Scholar 

  23. 23.

    Sandermann W, Schlumbom F (1962) On the effect of filtered ultraviolet light on wood. I. Photometric and chromatographic investigations on wood powders. Holz als Roh-u Werkstoff 20:245–252

    CAS  Article  Google Scholar 

  24. 24.

    Pan X, Lachenal D (1993) Structure and reactivity of spruce mechanical pulp lignins. III. Bleaching and photoyellowing of isolated lignin fractions. J Wood Chem Technol 13:145–165

    CAS  Article  Google Scholar 

  25. 25.

    Castellan A, Vanucci C, Laurent FIB (1987) Photochemical degradation of lignin through a C-O bond cleavage of non phenolic benzyl aryl ether units: a study of the photochemistry of a (2′,4′,6′ trimethyl-phenoxy)-3,4 dimethoxy toluene. Holzforschung 41:231–238

    CAS  Article  Google Scholar 

  26. 26.

    Vanucci C, Violet PFD, Laurent HB, Castellan A (1988) Photodegradation of lignin: a photophysical and photochemical study of a non-phenolic α-carbonyl β-O-4 lignin model dimer, (3,4dimethoxy-a-2′-methoxyphenoxy) acetophenone. J Photochem Photobiol A 41:251–265

    CAS  Article  Google Scholar 

Download references

Author information



Additional information

Part of this paper was presented at the 46th Annual Meeting of Japan Wood Research Society at Kumamoto, April 1996

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Kawamura, F., Miyachi, M., Kawai, S. et al. Photodiscoloration of western hemlock (Tsuga heterophylla) sapwood III Early stage of photodiscoloration reaction with lignans. J Wood Sci 44, 47–55 (1998).

Download citation

Key words

  • Tsuga heterophylla sapwood
  • Photodiscoloration
  • Phenoxy radical
  • Quinonemethide intermediate
  • Lignan