Larch

Scientific Name(s):Larch ( Larix ) species include: L. dahurica L., L. decidua Mill ( L. europaea ), L. eurolepis Gord., L. gmelinii , L. kaempferi , L. laricina Koch., L. leptolepis (Sieb. et Zucc.) Gord., L. occidentalis Nutt., and L. sibirica ledeb. Family: Pinaceae.

Common Name(s): Larch , Larix , Mongolian Larchwood ( L. dahurica )

Uses

Arabinogalactan, present in some larch species, has been reported to stimulate the immune system, to exhibit anti-inflammatory actions, and may enhance vascular permeability. Larchwood possesses astringent and diuretic actions. Its antiseptic actions may be useful in treating cystitis, respiratory problems, and wounds.

Dosing

The balsam of larch is used at a concentration of 10% to 20% in gels and ointments for colds and fevers. No clinical trials have been published addressing its safety or efficacy.

Contraindications

Use with caution in patients with kidney disease.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

None well documented.

Adverse Reactions

No adverse effects have been reported with use.

Toxicology

Research reveals little or no information regarding toxicology with the use of this product.

Botany

Larch trees are deciduous conifers. One example, L. decidua , grows to 50 m and has needle-like leaves and small, light brown cones. 1

History

Larch trees were said to have been introduced into Great Britain in 1639 and cultivated there since the early 19th century. The tree is grown mainly for its timber, but the inner bark and resin are also used. 1 Arabinogalactan constituents from certain Larix species have gained popularity because of their ability to enhance the immune system. 2

Chemistry

Arabinogalactans are present in species L. dahurica and L. occidentalis . 3 , 4 , 5 Arabinogalactans are long, densely branched, high molecular weight polysaccharides found throughout the plant kingdom and in some microbial systems. They are abundant in the genus Larix and are most often covalently linked to pectin and protein. 2 , 3 The powdered extract from the pine bark of the western larch tree, for example, is 98% arabinogalactan. This substance has a pine odor, a sweet taste, and is easily soluble in water. 2 All arabinogalactans isolated thus far from Larix , are the 3,6-beta-D-galactan type. 3 The extract is harvested from already fallen trees, otherwise a waste product from the lumber industry. A benefit of this natural polymer is that it possesses great uniformity. Batch variation is not a problem among larch trees that it is with other natural products. 2 Arabinogalactans from L. occidentalis have been isolated, characterized, and purified as discussed in one report. 5 Properties of arabinogalactans from L. dahurica have been documented as well, finding a homogeneous product with very narrow molecular weight distribution. 3

Other constituents from Larix have been identified. Larix flavonoids from various species have been analyzed, including flavanones (naringenin, hesperitin, hesperidin), flavones (apigenin, vitexin), and flavonols (kaempferols, quercetins, isorhamnetins, myricetins, and syringetins). 6 L. decidua contains lignans, resins, and volatile oil (mainly alpha- and betapinene and limonene). 1 18-nor-abietatrienes and diterpenes, including abietane-type diterpenes (eg, 7alpha,15-dihydroxyabieta-8,11,13-trien-18-al), have been isolated from species L. kaempferi . 7 , 8 Phenolics (flavonoids) from L. leptolepis have been reported. 9 Resin constituent diterpene from L. europaea has been documented. 10

Uses and Pharmacology

Arabinogalactan displays moisture retention, flavor encapsulation, film-forming capabilities, and desirable viscosities for a pleasant feeling in the mouth as both a natural and functional food ingredient. 2 Also, its role as a dietary fiber and its solubility properties make arabinogalactan an important polysaccharide. Its properties may be influenced by different side chain moieties on the molecule. 3

Arabinogalactan's role as an immune-boosting phytochemical has gained popularity. It has been reported to stimulate macrophages and other immune system components better than echinacea, although echinacea contains some arabinogalactans. Arabinogalactans have also been reported to increase the release of interferons, tumor necrosis factors, and interleukins, all of which are known to enhance immune function.

Animal data

Liver metastases in animals have been inhibited by arabinogalactans. 2 Human peripheral blood mononuclear cells and other cell lines have shown enhancement of natural killer cytotoxicity against certain tumor cells when pretreated with arabinogalactans extracted from L. occidentalis . 11

Arabinogalactan has properties that make it an ideal carrier to deliver agents to hepatocytes via the asialoglycoprotein receptors. Of radiolabeled arabinogalactans, 52.5% (4 mg/kg) were identified in the livers of rats receiving IV injection. 4 Arabinogalactan is highly bound to this receptor in both in vitro and in vivo experimentation. In one study, it was reported that those arabinogalactans with a lower molecular weight may be more desirable for hepatic drug delivery than others. 5 In another study, arabinogalactan conjugated with the antiviral vidarabine was effective in suppressing serum viral DNA titers in woodchucks infected with the hepatitis virus. 12

Clinical data

Research reveals no clinical data regarding the use of larch for immune-boosting effects.

Other uses

Arabinogalactan has also been reported to exhibit anti-inflammatory actions, and it may enhance vascular permeability. 2

L. laricina inhibited xanthine oxidase, thereby reducing uric acid formation, in a study of plant remedies used for gout. This was the greatest inhibition seen among the 26 species from 18 families that were evaluated. 13

Larchwood ( L. decidua ) also possesses astringent and diuretic actions. Its antiseptic actions may be useful in treating cystitis, respiratory infections, and wounds. 1

Dosage

The balsam of larch is used at a concentration of 10% to 20% in gels and ointments for colds and fevers. No clinical trials have been published addressing its safety or efficacy. 14

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

None well documented.

Adverse Reactions

There is no apparent allergy or toxicity to larch-derived arabinogalactans. 2 One source advises caution with the use of L. decidua in patients suffering from kidney disease. 1

Toxicology

Arabinogalactan produced no adverse reactions in single IV doses administered to mice at 5000 mg/kg or at repeated doses in rats for 90 days at 500 mg/kg/day. 4

Bibliography

1. Chevallier A. Larch. Encyclopedia of Medicinal Plants . New York: DK Publishing, 1996;224.
2. Benedikt H. Arabinogalactans: New Immune Boosting Fiber. Natural Pharmacy 1999;3:12.
3. Odonmazig P, et al. Structural and molecular peoperties of the arabinogalactan isolated from Mongolian larchwood ( Larix dahurica L.). Carbohydr Res 1994;252:317-24.
4. Groman E, et al. Arabinogalactan for hepatic drug delivery. Bioconjug Chem 1994;5(6):547-56.
5. Prescott J, et al. Larch arabinogalactan for hepatic drug delivery: isolation and characterization of a 9 kDa arabinogalactan fragment. Carbohydr Res 1995;278(1):113-28.
6. Niemann G, et al. Phenolics from Larix needles. XΙΙΙ. Analysis of main Larix flavonoids by high-pressure liquid chromatography. Planta Med 1977;31(3):297-301.
7. Ohtsu H, et al. 18-nor-Abietatrienes from the cones of Larix kaempferi. J Nat Prod 1998;61(3):406-408.
8. Ohtsu H, et al. Abietane diterpenoids from the cones of larix kaempferi. J Nat Prod 1998;61(10):1307-9.
9. Niemann G. Phenolics from Larix needles. 8. Flavonoids of L. leptolepis. Planta Med 1974;26(2):101-3.
10. Bruns K. Diterpene. VΙ. Neutral constituent of the resin from Larix europaea D.C. Tetrahedron 1969;25(8):1771-75.
11. Hauer J, et al. Mechanism of stimulation of human natural killer cytotoxicity by arabinogalactan from Larix occidentalis. Cancer Immunol Immunother 1993;36(4):237-44.
12. Enriquez P, et al. Conjugation of adenine arabinoside 5′-monophosphate to arabinogalactan: synthesis, characterization, and antiviral activity. Bioconjug Chem 1995;6(2):195–202.
13. Owen P, et al. Xanthine oxidase inhibitory activity of northeastern North American plant remedies used for gout. J Ethnopharmacol 1999;64(2):149-60.
14. Gruenwald J, ed. PDR for Herbal Medicines . 2nd ed. Montvale, NJ: Thomson Medical Economics; 2000: 457-458.

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