Botanical Name: Salix alba, Salicaceae

Common names: White Willow, Willow

Similar species: There are over 500 species in the Salix genus, most of which are generally considered by herbalists to be similar to Salix alba, which is considered to be officinal.  This includes old world species such as s. fragilis, S. purpurea, S. daphnoides S. babylonica and S. viminalis, as well as North American species such as S. nigra, S. hookeriana, S. lucida, S. scouleriana, S. sitchensis, and S. barclayi.  Many of the species in the only other genera in the Salicaceae, such as Populus tremuloides, are considered to be very similar to Salix, although some such as Populus balsamifera are harvested for its resin, rather than the bark or leaves.

Plant description: The various species of Willow present some enormous difficulties when it comes to sorting them out, even to the trained botanist.  Individual species can display a high degree of variability, and hybridization is common.  Generally speaking, Willow can be recognized by the single scale on the leaf bud, and the tiny flowers contained in dense spikes called catkins, with male and female catkins on separate shrubs or trees.  Although there are many species of Willow that are small shrubs, or occur en masse in dense thickets, the European White Willow can be a very large singular tree, from 8 to 24 meters in height, with many round, widely spreading branches.  New branches have a greenish smooth bark, but as they age the bark becomes very thick, cracked and grayish-brown. The grayish-green leaves are alternate, on short petioles, lanceolate to elliptically lanceolate, broadest a little above the middle, tapering toward each end, the margin serrate.  They are covered in silvery hairs, primarily on the lower surface, found most plentifully on the younger leaves.  The tiny inconspicuous yellowish flowers are borne in catkins on short stalks, with 3 or 4 spreading, leafy bracts, terminal, cylindrical, and elongated. The seed capsule ovate, brown, smooth, and small.

Habitat, ecology and distribution: White Willow is originally native to Europe, introduced to temperate North America as an ornamental and used by farmers on the prairies as a windbreak. Willow trees can be found almost anywhere in temperate areas of the world, from the coastal regions up into the subalpine, and even into the artic tundra. Willows are water-loving plants first and foremost, and can be easily found along rivers and streams, in floodplains and along lakeshores, in wet meadows, thickets and open moist forests.
Part used: catkins, leaves, bark.

History: According to the English herbalist Culpepper Willow is governed by the Moon, and perhaps because of this Willow seems to maintain a kind of quiet but nonetheless ubiquitous anonymity in the background of the forest, defying easy botanical classification.  Willow has given freely of herself however, and has been used for countless millennia all over the world as both a medicine and in technology, as a tool or in construction.  Willow is no doubt familiar to the human psyche, and like the moon during the Middle Ages, anyone who points out its virtues to an enthusiastic degree may be taken as a kind of lunatic that belongs at the herbal funny farm.  In 1838 Willow yielded the glycoside salicin, isolated from her bark in 1838 by the Italian chemist Rafaele Piria.  Salicin derived from Willow bark later served as the crude resource for the development and production of acetylsalicylic acid or aspirin during Nazi Germany.  Since that time Willow has once again retained her quiet role, the matter-of-fact take on Willow that it is nothing more than a kind of lethargic and weak-kneed precursor of its (mutant) child, aspirin.   

Constituents: The constituents in the various species of Salix are generally taken to be somewhat similar by herbalists, but are probably found with a high degree of variability, even within the same species.  This is likely due to specific ecological factors that may be reflected in the botanical diversity of Willow.  For this reason Willow is often marketed as a standardized extract, containing a specified amount of the phenolic glycoside salicin.  The reported salicin content in White Willow is among the lowest of the Willows, at about 0.5%, compared to S. fragilis, S. daphnoides and S. purpurea which are stated to contain upwards of 1-10% salicin.  Other related phenolic glycosides in Willow includes salicortin, salireposide, picein and triandrin, as well as acetylated salicin, salicortin and salireposide, and esters of salicylic acid and salicyl alcohol.  Willow however is also noted for its tannin content, reported from 3.3 to 20% in the leaves and bark.  These include tannins of the catechin type, with variable amounts of gallo tannins, as well as condensed tannins derived from catechin and epicatechin. Other constituents include flavonol glycosides, including narigenin, isosalipurpuroside and isoquercitin.  By some reports the pattern of phenolic glycosides in the leaves and the bark are identical (Duke 2002; Newall et al 1996, 268; Bradley et al 1992, 224; Felter and Lloyd 1893).

Medical Research: The compound salicin is hydrolyzed in the intestinal mucosa into its aglycone saligenin, which is then absorbed and then oxidized in the blood and liver into salicylic acid.  Although maintaining similar anti-inflammatory effects as acetylsalicylic acid, salicylic acid has significantly fewer side effects, and no activity on platelet function (Bradley et al 1992, 224).  The usefulness of Willow however appears to extend beyond its salicin content. Researchers evaluated the pharmacokinetics of salicin and its major metabolites in ten healthy volunteers after oral administration of a standardized Willow bark extract corresponding to 240 mg salicin, given in two equal doses at the outset of the study and three hours later. Over a period of 24 hours, the urine and serum levels of salicylic acid and its metabolites were determined using reverse-phase high-performance liquid chromatography. Salicylic acid was determined as the major metabolite of salicin detected in the serum (86% of total salicylates), besides salicyluric acid (10%) and gentisic acid (4%). Peak serum levels of salicylic acid were on average 1.2 mg/l, the serum concentration time curve equivalent to 87 mg acetylsalicylic acid.  The researchers concluded that the formation of salicylic acid alone is therefore unlikely to explain analgesic or anti-rheumatic effects of Willow bark (Schmid et al 2001).
•Arthritis and joint pain: In a placebo-controlled blinded clinical trial, 210 patients with chronic low back pain received either an oral Willow bark extract with either 120 mg (low dose) or 240 mg (high dose) of salicin, or placebo, in a 4-week blinded trial. The principal outcome measure was the proportion of patients who were pain-free without the NSAID tramadol for at least 5 days during the final week of the study. The percentage of pain-free patients in the last week of treatment were 39% in the group receiving high-dose extract, 21% in the group receiving low-dose extract, and 6% in the placebo group.  The response in the high-dose group was evident after only 1 week of treatment (Chubaski et al 2000). A Willow bark extract, provided in a dose corresponding to 240 mg of salicin per day, was compared to placebo in a 2-week, double-blind, randomized controlled trial of 78 arthritic patients. A statistically significant difference between active treatment and placebo group was observed in all dimensions of assessment, indicating the superiority of willow bark extract over placebo (Schmid et al 2000). Researchers compared the effects of a proprietary extract of Willow bark and rofecoxib, a selective inhibitor of the enzyme cyclo-oxygenase-2 (COX-2), in an open, randomized, post-marketing study of patients with acute exacerbations of low back pain over a 6-month period. Using computer-generated random list, 114 patients were allocated to receive a daily dose of herbal extract containing 240 mg of salicin and 114 were allocated to receive 12.5 mg of the synthetic COX-2 inhibitor rofecoxib.  All patients were free to use whatever additional conventional treatments were thought necessary. The researchers report that the outcome measures were well matched between the two therapies, with a similar incidence of adverse effects.  The researchers conclude that because there is no significant difference between them, the Willow bark was a better therapy simply because it was less expensive (Chrubasik et al 2001).
•Cardiovascular: In a randomized double-blind clinical study of 51 patients researchers investigated if Willow bark affects platelet aggregation.  Thirty-five patients suffering from acute exacerbations of chronic low back pain received either Willow bark extract standardized to 240 mg salicin/day or placebo.  A further sixteen patients with stable chronic ischemic heart disease were given 100 mg acetylsalicylate per day.  Platelet aggregation was studied using an aggregometer, with arachidonic acid, adenosine di-phosphate and collagen as the aggragating agents.  Willow bark was found to have a minimal effect upon platelets (Krivoy et al 2001).

Toxicity: Duke reports an oral LD50 for salicin administration in rats as 1890 mg/kg (1985, 542).

Herbal action: bitter tonic, astringent, styptic, analgesic, anti-inflammatory, antipyretic

Indications: atonic dyspepsia, catarrhal states of the digestive, respiratory and genitourinary tract, diarrhea, dysentery, intermittent fever, spermatorrhea, prostatitis, cystitis, and ovaritis, passive hemorrhage, atonic menorrhagia, leucorrhea

Contraindications and cautions: Individuals sensitive to aspirin and other salicyclates such probably avoid Willow bark.  Concurrent administration of Willow with salicylate drugs, as well as methotrexate, anticoagulants and other cardiovascular drugs is best avoided.  Large doses and standardized extracts should be avoided in pregnancy and lactation.

Medicinal uses: Willow bark is an important bitter tonic with marked astringent properties, making it useful in chronic hypersecretory states, such as mucus discharges, passive hemorrhage, leucorrhea, humid asthma, diarrhea and dysentery.  In the treatment of inflammatory joint disease Willow is unlikely to provide the same relief as aspirin, and if applied as a simple for its salicin content, will typically require such large doses that the tannins become potentially toxic (Bergner 2001).  Nonetheless Willow leaf and bark have been traditionally used as anti-inflammatory and analgesic agents in conditions such as arthritis and gout, although it is probably better suited as a preventative, in mild to moderate conditions, or when taken over the long term as a decoction or infusion.  Combined with other herbs such as Zingiber and Curcuma, Willow helps to address a broad range of musculoskeletal symptoms and acts to relieve chronic pain.  Willow has long been considered to be an important remedy in intermittent fevers, but is avoided at the first onset of a fever.  Culpepper thought Willow a useful herb for hemorrhages generally, taken both internally and applied externally over wounds and cuts.  Willow is equally useful when used as a fomentation for indolent ulcers.  Both Culpepper and Galen thought Willow to some extent a useful hepatic remedy in the treatment dandruff and skin blemishes.  Culpepper states that Willow is an anaphrodisiac, a view latter confirmed by the Eclectics, who describe Willow as an important therapeutic agent in "…libidinous suggestions and lascivious dreams terminating in pollutions" and in "…extreme forms of sexual perversion, satyriasis, erotomania, and nymphomania" (Felter and Lloyd 1893).  For this purpose the Eclectics preferred a decoction of the catkins of Salix nigra.  To this extent Willow was considered a helpful treatment in spermatorrhoea and in atonic states of the reproductive system, especially where those parts had suffered from recent 'overuse'. 

Pharmacy and dosage:
•Fresh Plant Tincture: catkins, leaves, bark, 1:2, 95% alcohol, 3-60 gtt
•Dry Plant Tincture: dried bark, 1:5, 1-5 mL
•Cold Infusion: fresh aerial parts, 1:20, 200 mL
•Decoction: catkins, bark, 1:20, 60-90 mL
•Powder: 3-5 g

REFERENCES

Bergner, Paul. 2001. Salix: Willow bark and NSAID. Medical Herbalism: Materia Medica and Pharmacy. Originally published in Medical Herbalism 3(2):7. Boulder, CO: Bergner Communications
Bradley, Peter R. ed. 1992. British Herbal Compendium. Bournemouth, UK: British Herbal Medicine Association.
Chrubasik S, Kunzel O, Model A, Conradt C, Black A. 2001. Treatment of low back pain with a herbal or synthetic anti-rheumatic: a randomized controlled study. Willow bark extract for low back pain. Rheumatology Dec;40(12):1388-93
Chrubasik S, Eisenberg E, Balan E, Weinberger T, Luzzati R, Conradt C. 2000. Treatment of low back pain exacerbations with willow bark extract: a randomized double-blind study. Am J Med Jul;109(1):9-14
Cook, WM. H. 1869. The Physiomedical Dispensatory.  Cincinnati: self-published.  Digitized version available from http://medherb.com/cook/home.htm.
Duke, James. 1985. CRC Handbook of Medicinal Herbs. Boca Raton: CRC Press.
Evans, W.C. 1989. Trease and Evans Pharmacognosy London: BailliËre Tindall.
Felter, HW and JU Lloyd. 1893. King's American Dispensatory. Digitized version available from http://www.ibiblio.org/herbmed/eclectic/kings/main.html.
Krivoy N, Pavlotzky E, Chrubasik S, Eisenberg E, Brook G. 2001. Effect of salicis cortex extract on human platelet aggregation. Planta Med Apr;67(3):209-12
Moore, Michael.  1979. Medicinal Plants of the Mountain West. Santa Fe: Museum of New Mexico Press
Newall, Carol A., Linda A. Anderson and J.D. Phillipson. 1996. Herbal Medicines: A Guide for Health-Care Professionals. London: The Pharmaceutical Press.
Schmid B, Kotter I, Heide L. 2001. Pharmacokinetics of salicin after oral administration of a standardised willow bark extract. Eur J Clin Pharmacol Aug;57(5):387-91
Schmid B, Ludtke R, Selbmann HK, Kotter I, Tschirdewahn B, Schaffner W, Heide L. 2000. Effectiveness and tolerance of standardized willow bark extract in arthrosis patients. Randomized, placebo controlled double-blind study. Z Rheumatol Oct;59(5):314-20
Weiss, Rudolf. 1988. Herbal Medicine. Translated by A.R. Meuss. Beaconsfield, England: Beaconsfield Publishers