Salicylate-containing Herbs
Summary
Salicylate-containing Herbs
introduction: Salicylates have long been known as water soluble compounds derived from a number of plants, particularly Willow (Salix
spp.) and Meadowsweet (Spirea spp.) with analgesic, antipyretic and anti-inflammatory properties. Following the identification of salicin as the active principle of Willow bark, and the subsequent synthesis of acetylsalicylic acid (aspirin), the use of natural salicylates has declined.
chemistry of salicylates:
Plant salicylates occur as phenolic glycosides, most commonly salicin, which is the glycoside of salicyl alcohol, or the related populin (benzoyl alcohol glycoside). Methyl salicylate, derived from
Gaultheria spp. (Wintergreen) also exists as a glycoside. The properties of naturally derived salicylic acid are similar to those of aspirin, which basically involve the inhibition of prostaglandin synthesis by inactivation of COX1. However, the natural form presents important differences in bioavailability and pharmacokinetic properties from pharmaceutical aspirin due to both the glycoside linkage and the absence of the acetyl group.
bioavailability of salicin and salicylate decomposition products:
Salicin is hydrolyzed to salicyl alcohol and glucose by intestinal flora. Salicyl alcohol is subsequently oxidized by the liver to salicylic acid. The largest percentage of the compounds are excreted in the urine as salicylic acid conjugates after phase 2 hepatic processing, but salicin, salicyl alcohol and salicylic acid are also excreted unchanged in small amounts.
overview of pharmacokinetic interactions:
• The importance of this biotransformation scheme is that salicin and related plant phenolic glycosides do not have the same tendency as aspirin to cause gastric hemorrhage.
• The kinetics of hydrolysis and oxidation also mean that a single dose of salicin maintains a steady state plasma concentration for up to 8 hours following ingestion, while pharmaceutical doses need to be repeated 3-4 hourly to maintain plasma levels.
• Alkaloids: It has been suggested that salicylate-containing herbs may precipitate alkaloid containing drugs upon concurrent ingestion, presumably due to the presence of the phenolic grouping: the evidence for this is lacking, and the commercial availability of salicylate- alkaloidal preparations combining, for example codeine and aspirin, would tend to suggest this interaction is not a major issue. It should be noted that many salicylate-containing herbs also have high tannin content.
pharmacodynamic interactions:
• Lack of adverse effects: Salicin and its decomposition products are less effective as prostaglandin inhibitors (COX1 is inhibited by acetylation), and are less effective as platelet aggregation inhibitors for use in the prophylaxis of stroke and thrombus formation.
• Caution in substitution: While salicylate-containing plants are essentially free from the adverse effects and interactions that occur with synthetic salicylate drugs, at the same time caution is required before substituting prescribed salicylates with salicylate-containing herbs for blood thinning, since salicylate-containing herbs are less effective.
• Free salicylic acid and trace quantities of related phenolic glycosides are widely distributed among many foods, particularly fruits. Due to the minute concentrations involved these plants are considered unimportant as medicinal herbal sources of salicylates and are not listed here. Some authorities consider the ingestion of these foods to be associated with various conditions, notably Attention Deficit issues in children.
Herbs
Common salicylate-containing herbs:
• Betula lenta (Sweet Birch)
• Betula pendula (White birch)
• Filipendula ulmaria (Meadowsweet)
• Gaultheria procumbens (Wintergreen)
• Populus balsamifera (Balsam Poplar)
• Populus nigra (Black Poplar)
• Populus candicans (Balm Of Gilead)
• Salix alba (White Willow)
• Viburnum prunifolium (Black Haw)
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Do not rely solely on the information in this article.
The information presented in Interactions is for
informational and educational purposes only. It is based on scientific
studies (human, animal, or in vitro), clinical experience, case
reports, and/or traditional usage with sources as cited in each
topic. The results reported may not necessarily occur in all
individuals and different individuals with the same medical conditions
with the same symptoms will often require differing treatments. For
many of the conditions discussed, treatment with conventional medical
therapies, including prescription drugs or over-the-counter
medications, is also available. Consult your physician, an
appropriately trained healthcare practitioner, and/or pharmacist for
any health concern or medical problem before using any herbal products
or nutritional supplements or before making any changes in prescribed
medications and/or before attempting to independently treat a medical
condition using supplements, herbs, remedies, or other forms of
self-care.
References
Bone K. Herbal Pharmacokinetics - The Behaviour of Large Molecules. In Proceedings NHAA International Conference, Sydney, Australia. 1998.
Brinker F. Herb Contraindications and Drug Interactions. Second edition., Sandy, OR: Eclectic Institute Inc, 1998.
Duke JA. Handbook of Phytochemical Constituents of GRAS Herbs and Other Economical Plants.
CRC Press. 1994.
Hoffmann D. Phytochemistry. (Forthcoming title, in press 1999, publisher to be confirmed).
McGuffin M, et al.(eds.) AHPA Botanical Safety Handbook. CRC Press, 1997.