FWD 2 Expanded Commission E: Willow bark

Herbal Medicine: Expanded Commission E

Willow bark

Latin Name: Salix alba, S. purpurea L., S. fragilis L.
Pharmacopeial Name: alicis cortex
Other Names: bay willow (S. pentandra L.); crack willow (S. fragilis L.); purple willow (S. purpurea L.); violet willow (S. daphnoides Villars); white willow (S. alba L.)

Overview

Willow is a deciduous shrub native to Britain, central and southern Europe (Karnick, 1994), Asia, and North America (Wichtl and Bisset, 1994). The material of commerce comes mainly from southeastern European countries, including Bulgaria, Hungary, Romania, the former Yugoslavia (BHP, 1996; Wichtl and Bisset, 1994), and the United Kingdom (BHP, 1996).

Some of the modern therapeutic applications for willow bark originate from its early uses in ancient Greek medicine, which were first reported by Dioscorides in his herbal De Materia Medica written in the first century C.E. (Bown, 1995). During the Middle Ages, willow bark was used in Europe to reduce fevers and relieve pain. Willow's anti-inflammatory and fever-reducing actions are attributed to salicylates in the bark. These glycosidic constituents were first isolated by a French chemist in 1829, and were synthesized six years later (Schulz et al., 1998). Salicylic acid, first isolated from meadowsweet leaf (Filipendula ulmaria; syn. Spiraea ulmaria), is the phytotherapeutic precursor of acetylsalicylic acid, the analgesic drug now commonly known as aspirin (Bradley, 1992; Weissman, 1991; Wichtl and Bisset, 1994).

A few human studies have been found in the literature. In one double-blind study, researchers at the Centre for Complementary Health Studies at the University of Exeter in England investigated the effect of Reumalex, an over-the-counter herbal drug containing willow bark, on 82 participants suffering with chronic arthritic pain. The subjects were randomly assigned without crossover to either Reumalex or placebo. The duration of the study was two months, resulting in a small though statistically significant improvement in pain symptoms. The researchers concluded that Reumalex exhibits a mild analgesic effect in chronic arthritis at a level appropriate for self-medication (Mills et al., 1996). In a recent pilot study, the use of Salix SST, a saliva-stimulating lozenge, was subjectively evaluated as a treatment for the relief of radiation-induced xerostomia (dryness in the mouth) in 10 patients for seven days. The researchers reported a statistically significant improvement in the dryness and general comfort of the mouth as well as improved sleep and speech (Senahayake et al., 1998). In a pharmacokinetic study in humans, three tablets containing willow bark extract (standardized to provide a total dose of 55 mg salicin) were administered to 12 male volunteers in three doses over a period of eight hours. The study calculated that the half-life of the plasma was approximately 2.5 hours (ESCOP, 1997; Pentz et al., 1989).

In Germany, willow bark is official in the German Pharmacopeia and approved in the Commission E monographs. It is used as a main component of some analgesic and antirheumatic drugs (Wichtl and Bisset, 1994) such as Kneipp Rheuma-Tee N (Kneipp, 1996). In German pediatric medicine, willow bark is used as an antipyretic component of various herbal preparations, particularly in combination with diaphoretic herbs. For example, an effective herbal tea prescribed for children with influenza is composed of 30% willow bark (Salix species), 40% linden flower (Tilia species), 10% meadowsweet flower (F. ulmaria), 10% German chamomile flower (Matricaria recutita), and 10% bitter orange peel (Citrus aurantium). Willow bark is also used to treat children with pain in the extremities due to cold and flu (Schilcher, 1997). Throughout the United States and Canada, willow barks of several different species are used extensively in traditional aboriginal medicines from the Seminole people in Florida to the Eskimos in Alaska. For example, the Cherokee prepare an infusion of white willow bark (Salix alba) as a febrifuge drug to treat fever. The Blackfoot prepare a decoction of pussy willow twigs (S. discolor) as an analgesic painkiller and also as a febrifuge drug. The Iroquois prepare an infusion of sandbar willow (S. interior) stems as an analgesic drug. The Eskimo prepare an infusion of tealeaf willow (S. planifolia ssp. pulchra) bark also as an analgesic drug (Moerman, 1998).

German pharmacopeial grade willow bark consists of the dried, whole, cut, or powdered bark from young branches of Salix purpurea L., S. daphnoides Villars or other comparable Salix species, collected in the early spring. It must contain not less than 1% total salicin calculated as salicin. Botanical identity must be confirmed by thin-layer chromatography (TLC) plus macroscopic and microscopic examinations (DAB 10, 19911996). In addition to the two above mentioned species, the British Herbal Pharmacopoeia specifically allows for S. alba L., S. fragilis L., and S. pentandra L. and also requires that the dried bark contain not less than 10% water-soluble extractive (BHP, 1996). ESCOP requires that the material comply with the qualitative and quantitative criteria of the German Pharmacopeia (ESCOP, 1997).

Description

Willow bark consists of the bark of the young, two to three year-old branches harvested during early spring of S. alba L., S. purpurea L., S. fragilis L., and other Salix species [Salicaceae] and their preparations in effective dosage. The bark contains at least 1% total salicin derivatives, calculated as salicin relative to the dried herb.

Chemistry and Pharmacology

Note: As the Commission E allows for several different Salix species, the quantities of certain constituents may vary significantly depending on the species used (Meier et al., 1985; Meier et al., 1988; Thieme, 1965). Constituents include 1.511% phenolic glycosides, mainly salicylates (1.010.2%), including salicin and its derivatives (salicortin and tremulacin) (Bradley, 1992; Thieme, 1965; Wichtl and Bisset, 1994); 820% tannins, mainly catechin tannins, some gallotannins and condensed tannins (procyanidins); and 14% flavonoids, including isoquercitrin, and naringin and its glucoside (Bradley, 1992; Wichtl and Bisset, 1994). The chemistry composition of the young twigs is comparable, though in lower concentrations than the bark alone (ESCOP, 1997). The species with the highest reported salicin content are S. purpurea, S. daphnoides, and S. fragilis (Meier et al., 1985; Wichtl and Bisset, 1994).

The Commission E reported antipyretic, antiphlogistic, and analgesic activities.

The British Herbal Pharmacopoeia reported anti-inflammatory action (BHP, 1996). The British Herbal Compendium additionally reported analgesic, antipyretic, antirheumatic, and astringent actions (Bradley, 1992). The Merck Index reported analgesic action for salicin, isolated from willow bark (Budavari, 1996).

Natural salicylic acid is reported to produce fewer side effects than the synthetic acetylsalicylic acid (Meier and Liebi, 1990; Mayer and Mayer, 1949). The analgesic action of willow bark is apparently due to inhibition of prostaglandin synthesis by its salicin derivatives, which cause sensitization of peripheral pain receptors (Schilcher, 1997). Metabolites of salicin and tremulacin have demonstrated anti-inflammatory activity in vitro (Albrecht et al., 1990). Other in vitro experiments have found that salicin is stable under acidic conditions. Both saligenin and salicin have been shown to bind to human serum albumin, but saligenin has a higher affinity (ESCOP, 1997; Steinegger and Hvel, 1972).

Uses

The Commission E approved willow bark for diseases accompanied by fever, rheumatic ailments, and headaches.

The British Herbal Compendium indicates its use for rheumatic and arthritic conditions and feverish conditions such as the common cold or influenza (Bradley, 1992). ESCOP indicates it use for treatment of feverish conditions, symptomatic treatment of mild rheumatic complaints, and relief of headache (ESCOP, 1997). In France, it is allowed for use as an analgesic to treat headache and toothache pain as well as painful articular conditions, tendinitis, and sprains (Bradley, 1992; Bruneton, 1995).

Contraindications

See Interactions with Other Drugs. Despite concerns expressed by some health professionals, there is no evidence that willow preparations should be contraindicated in small children with flu to produce Reyes syndrome; the salicylates in willow metabolize differently than aspirin (acetylsalicylic acid).

Side Effects

See Interactions with Other Drugs.

Use During Pregnancy and Lactation

No restrictions known.

Interactions with Other Drugs

Because of willow bark's active constituents, interactions like those encountered with salicylates may arise. However, studies conducted thus far do not indicate this potential toxicity.

Dosage and Administration

Unless otherwise prescribed: Liquid and solid preparations for internal use with an average daily dosage corresponding to 60-120 mg total salicin (Commission E), which is equivalent to 6-12 g dried bark (Schilcher, 1997).

Note: Combinations with diaphoretic herbs may be very effective.

Dried bark: 1-3 g, three times daily (HPB, 1992; Karnick, 1994; Newall et al., 1996).

Decoction: Place 2-3 g finely chopped or coursely powdered bark in 150-250 ml cold water, bring to a boil and simmer for 5 minutes, three to four times daily (Meyer-Buchtela, 1999; Wichtl, 1989; Wichtl and Bisset, 1994).

Fluidextract 1:1 (g/ml), 25% ethanol: 1-2 ml, three times daily (Bradley, 1992; HPB, 1992; Karnick, 1994).

Tincture 1:5 (g/ml), 25% ethanol: 5-8 ml, three times daily (Bradley, 1992).

Dry extract: Standardized to contain 20-40 mg of total salicin, three times daily (Bradley, 1992; ESCOP, 1997).

References

Albrecht, M. et al. 1990. Anti-inflammatory activity of flavonol glycosides and salicin derivatives from the leaves of Populus tremuloides. Planta Med 56:660.

Bown, D. 1995. Encyclopedia of Herbs and Their Uses. New York: DK Publishing, Inc. 345.

British Herbal Pharmacopoeia (BHP). 1996. Exeter, U.K.: British Herbal Medicine Association. 188.

Bradley, P.R. (ed.). 1992. British Herbal Compendium, Vol. 1. Bournemouth: British Herbal Medicine Association. 224226.

Bruneton, J. 1995. Pharmacognosy, Phytochemistry, Medicinal Plants. Paris: Lavoisier Publishing.

Budavari, S. (ed.). 1996. The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 12th ed. Whitehouse Station, N.J.: Merck & Co, Inc. 1432.

Deutsches Arzneibuch, 10th ed. (DAB 10). 1991. (With subsequent supplements through 1996.) Stuttgart: Deutscher Apotheker Verlag.

ESCOP. 1997. 'Salicis cortex.' Monographs on the Medicinal Uses of Plant Drugs. Exeter, U.K.: European Scientific Cooperative on Phytotherapy.

Health Protection Branch (HPB) Status Manual. 1992. Ottawa: Health Protection Branch. 212.

Karnick, C.R., 1994. Pharmacopoeial Standards of Herbal Plants, Vol. 1. Delhi: Sri Satguru Publications. 321322.

Kneipp, 1996. Wegweiser zu den Kneipp Mitteln [Guide to Kneipp Remedies]. W rzburg: Sebastian Kneipp Gesundheitsmittel-Verlag. 110111.

Mayer, R.A. and M. Mayer. 1949. Biologische Salicyltherapie mit Cortex Salicis (Weidenrinde). Pharmazie 4:7781.

Meier B., O. Sticher, A. Bettschart. 1985. Weidenrinde-Qualitt. Gesamtsalicinbestimmung in Weidenrinden und Weidenprparaten mit HPLC. Dtsch Apoth Ztg 125:341347.

Meier, B. et al. 1988. Pharmaceutical aspects of the use of willows in herbal remedies. Planta Med 54:559560.

Meier, B. and M. Liebi. 1990. Salicinhaltige pflanzliche Arzneimittel. berlegungen zu Wirksamkeit und Unbedenklichkeit. Z Phytother 11:5058.

Meyer-Buchtela, E. 1999. Tee-RezepturenEin Handbuch f r Apotheker und rzte. Stuttgart: Deutscher Apotheker Verlag.

Mills, S.Y., R.K. Jacoby, M. Chacksfield, M. Willoughby. 1996. Effect of a proprietary herbal medicine on the relief of chronic arthritic pain: a double-blind study. Br J Rheumatol 35(9):874878.

Moerman, D.E. 1998. Native American Ethnobotany. Portland, OR: Timber Press. 500509.

Newall, C.A., L.A. Anderson, J.D. Phillipson. 1996. Herbal Medicines: A Guide for Health-Care Professionals. London: The Pharmaceutical Press. 268269.

Pentz, R. et al. 1989. Bioverf gbarkeit von Salicylsure und Coffein aus einem phytoanalgetischen Kominationsprparat. Dtsch Apoth Ztg (10):9296.

Schilcher, H. 1997. Phytotherapy in Paediatrics: Handbook for Physicians and Pharmacists. Stuttgart: Medpharm Scientific Publishers. 41, 6364.

Schulz, V., R. Hnsel, V.E. Tyler. 1998. Rational Phytotherapy: A Physicians' Guide to Herbal Medicine. New York: Springer.

Senahayake, F., K. Piggott, J.M. Hamilton-Miller. 1998. A pilot study of Salix SST (saliva-stimulating lozenges) in post-irradiation xerostomia. Curr Med Res Opin 14(3):155159.

Steinegger, E. and H. Hvel. 1972. Analytische und biologische untersuchungen an Salicaceen-wirkstoffen, insbesondere an salicin. II. Biologische untersuchungen [Analytic and biologic studies on Salicaceae substances, especially on salicin. II. Biological study]. Pharm Acta Helv 47(3):222234.

Thieme, H. 1965. Die Phenolglykoside der Salicaceen. Planta Med 13:431438.

Weissman, G. 1991. Aspirin. Scientific Am (Jan.):5864.

Wichtl, M. (ed.). 1989. Teedrogen, 2nd ed. Stuttgart: Wissenschaftliche Verlagsgesellschaft.

Wichtl, M. and N.G. Bisset (eds.). 1994. Herbal Drugs and Phytopharmaceuticals. Stuttgart: Medpharm Scientific Publishers. 437439.

Additional Resources

British Herbal Pharmacopoeia (BHP). 1983. Keighley, U.K.: British Herbal Medicine Association.

. 1990. Exeter, U.K.: British Herbal Medicine Association.

Deutsches Arzneibuch, 10th ed. Vol. 16. (DAB 10). 1991. Kommentar. Stuttgart: Wissenschaftliche Verlagsgesellschaft.

Dorsch, W. et al. 1993. Empfehlungen zu Kinderdosierngen von monographierten Arzneidrogen und ihren Zubereitungen. Bonn: Kooperation Phytopharmaka.

Felter, H.W. and J.U. Lloyd. 1985. King's American Dispensatory, Vols. 12. Portland, OR: Eclectic Medical Publications [reprint of 1898 original].

Hnsel, R. 1991. Phytopharmaka, 2nd ed. New York: Springer Verlag.

Hutchens, A. 1991. Indian Herbology of North America. Boston: Shambala.

Meier, B. 1989. Pflanzliche versus synthetische Arzneimittel. Schweiz Apoth Ztg (127):472477.

Schaffner, W. 1991. Bericht ber die Pilot-Studie Zeller-Rheumadragees forte/gewisse Rheumaformen. Pharmazeutisches Institut der Universitt Basel. Unpublished report for Max Zeller Shne AG, CH-8590 Romanshorn.

Tyler, V.E. 1994. Herbs of Choice: The Therapeutic Use of Phytomedicinals. New York: Pharmaceutical Products Press.

Wagner, H. and M. Wiesenauer. 1995. Phytotherapie. New York: Gustav Fischer Verlag.

Wren, R.C. 1988. Potter's New Cyclopaedia of Botanical Drugs and Preparations. Essex: The C.W. Daniel Company Ltd.

This material was adapted from The Complete German Commission E MonographsTherapeutic Guide to Herbal Medicines. M. Blumenthal, W.R. Busse, A. Goldberg, J. Gruenwald, T. Hall, C.W. Riggins, R.S. Rister (eds.) S. Klein and R.S. Rister (trans.). 1998. Austin: American Botanical Council; Boston: Integrative Medicine Communications.

1) The Overview section is new information.

2) Description, Chemistry and Pharmacology, Uses, Contraindications, Side Effects, Interactions with Other Drugs, and Dosage sections have been drawn from the original work. Additional information has been added in some or all of these sections, as noted with references.

3) The dosage for equivalent preparations (tea infusion, fluidextract, and tincture) have been provided based on the following example:

  • Unless otherwise prescribed: 2 g per day of [powdered, crushed, cut or whole] [plant part]
  • Infusion: 2 g in 150 ml of water
  • Fluidextract 1:1 (g/ml): 2 ml
  • Tincture 1:5 (g/ml): 10 ml

4) The References and Additional Resources sections are new sections. Additional Resources are not cited in the monograph but are included for research purposes.

This monograph, published by the Commission E in 1994, was modified based on new scientific research. It contains more extensive pharmacological and therapeutic information taken directly from the Commission E.

Excerpt from Herbal Medicine: Expanded Commission E Monographs
Copyright 2000 American Botanical Council
Published by Integrative Medicine Communications
Available from the American Botanical Council.