Larix occidentalis Nutt.

Last updated: 28 April 2016

Scientific Name

Larix occidentalis Nutt. 


Pinus nuttallii Parl., Larix americana var. brevifolia Carrière [1]

Vernacular Name

English Tamarack, western larch [2]
Italy Larice occidentale [3]
Denmark Vestamerikansk lærk [3]
Turkey Bati Amerika melez çami [3].

Geographical Distributions

Larix occidentalis is native in Western Canada and Northwest America [3]. It can be found in the Upper Colombia River Rasin of Southeast British Columbia, Northeast Washington along the east slopes of the Cascades in Washington and North-Central Oregan and in the Wallowa and Blue Mountains of Northeast Oregon and Southeast Washington. It is also occasionally seeded outside its natural range. [4] The plant grows best in well-drained soil. [5]

Botanical Description

L. occidentalis is a member of the Pinaceae family [1]. It is a large perennial tree [2][5].


No documentation.

Chemical Constituent

Arabinogalactan. [6]

Plant Part Used

No documentation.

Traditional Use

No documentation.

Preclinical Data


Cytotoxic activity

It has been reported that decreased NK cell activity may be linked to a variety of chronic diseases including cancer [7], chronic fatigue syndrome (CFS) [8][9], prostate cancer, autoimmune diseases such as multiple sclerosis [10], and viral hepatitis [11]

Arabinogalactan from L. occidentalis is reported to enhance immunity by various methods by stimulating natural killer (NK) cell cytotoxicity, enhances other functional aspects of the immune system, and inhibits the metastasis of tumor cells to the liver in vitro.  The larch arabinogalactan-mediated enhancement of NK cytotoxicity does not appear to be initiated directly, but may be governed by the cytokine network. Generally, arabinogalactan pretreatment induces an increased release of interferon gamma, tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6. Results suggested that the increase in interferon gamma was most responsible for the observed enhancement of NK cytotoxicity. These actions may have utility as components to support conventional therapies such as cancer treatment and HIV infection. Because of the immune-enhancing properties, arabinogalactan from L. occidentalis is receiving increased attention as a clinically useful immunomodulating agent. [12]


Arabinogalactan from L. occidentalis tree (5000 mg/kg) administered in single intravenous dose to mouse and a repeat dose (500 mg/kg/day) toxicity studies to rats for duration of 90 days showed no adverse reactions. Arabinogalactan is reported safe in recommended dosages and is FDA approved for a variety of food uses and applications. LA was reported less toxic than methylcellulose in laboratory studies.  [13]

Clinical Data

Clinical findings

Because of the immune-enhancing properties, arabinogalactan from L. occidentalis is receiving increased attention as a clinically useful immunomodulating agent. Arabinogalactan may be a good therapeutic choice for individuals with chronic immune system disturbances such as colds and influenza, chronic fatigue, and viral hepatitis among others. It has been used with success in children, specifically in otitis media. Unpublished evidence following a controlled study of larch arabinogalactan supplementation in human volunteers has similarly demonstrated an ability to promote an increase of bifidobacteria, as well as other anaerobes such as lactobacillus. [14]


No documentation.

Side effects

No documentation.

Pregnancy/Breast Feeding

No documentation.

Age limitation

No documentation.

Adverse reaction

No documentation.

Interaction & Depletion

No documentation.

Interaction with drug

Studies have reported that arabinogalactan stimulates human immune system, which may alter the effects of these medications and possibly the dose needed for treatment. [12] These drugs include azathioprine, basiliximab, cyclosporine, daclizumab, glatiramer, muromonab-cd3, mycophenolate mofetil, tacrolimus (FK506), sirolimus, methotrexate, prednisone, hydrocortisone, methylprednisolone, prednisolone, betamethasone, budesonide, triamcinolone, dexamethasone, cortisone

Interaction with other Herbs

No documentation.


No documentation.

Case Report

No documentation.


No documentation.

Poisonous Management

No documentation.

Line drawing

No documentation.


  1. The Plant List. Ver1.1. Larix occidentalis Nutt. [homepage on the Internet]. c2013 [updated 2012 Mar 23; cited 2016 Apr 26]. Available from:
  2. Quattrocchi U. CRC world dictionary of medicinal and poisonous plants: Common names, scientific names, eponyms, synonyms, and etymology. Volume III E-L. Boca Raton, Florida: CRC Press, 2012; p. 715.
  3. Wiersema JH, León B. World Economic Plants: A Standard Reference. 2nd ed. Boca Raton, Florida: CRC Press, 2016; p.390.
  4. United States Department of Agriculture. Schmidt WC, Shearer RC, Roe AL. Ecology and silviculture of western larch forests. Washington DC: USDA; 1976. Tech Bull 1520. p. 2.
  5. United States Department of Agriculture. Van Dersal WR. Native woody plants of the United States, their erosion-control and wildlife values. Washington DC: USDA; 1983. Miscellaneous Publication 303. p. 152.
  6. Prescott JH, Groman EV, Gulyas G. New molecular weight forms of arabinogalactan from Larix occidentalis. Carbohydr Res. 1997; 301:89-93.
  7. Parra S, Pinochet R, Vargas R, Sepúlveda C, Miranda D, Puente J. [Natural killer cytolytic activity in renal and prostatic cancer]. Rev Med Chil. 1994;122:630-637. Spanish
  8. Levine PH, Whiteside TL, Friberg D, Bryant J, Colclough G, Herberman RB. Dysfunction of natural killer activity in a family with chronic fatigue syndrome. Clin Immunol Immunopathol. 1998;88:96-104.
  9. Uchida A. Therapy of chronic fatigue syndrome. Nippon Rinsho. 1992;50:2679-2683. Japanese
  10. Kastrukoff LF, Morgan NG, Zecchini D, et al. A role for natural killer cells in the immunopathogenesis of multiple sclerosis. J Neuroimmunol. 1998;86:123-133.
  11. Corado J, Toro F, Rivera H, Bianco NE, Deibis L, De Sanctis JB. Impairment of natural killer (NK) cytotoxic activity in hepatitis C virus (HCV) infection. Exp Immunol. 1997;109:451-457.
  12. Hauer J, Anderer FA. Mechanism of stimulation of human natural killer cytotoxicity by arabinogalactan from Larix occidentalis. Cancer Immunol Immunother. 1993;36(4):237-44.
  13. Groman EV, Enriquez PM, Jung C, Josephson L. Arabinogalactan for hepatic drug delivery. Bioconjug Chem. 1994;5:547-556.
  14. Kelly G. Larch arabinogalactan: Clinical relevance of a novel immune-enhancing polysaccharide. Altern Med Rev. 1999;4(2):96-103.