Salicylates

Salicylates are a widely distributed group of simple phenolics, found in many flowering plant families including Salicaeace (Populus sp & Salix sp) and Caprifoliaceae (Viburnum sp.) and include compounds such as salicin, methyl salicylate & salicylic acid, with salicin being the first identified compound in this class and used to create the well known pharmaceutical drug Aspirin.

When willow bark research began in 1829 the crude extraction techniques isolated salicylic acid not salicin, from the bark. Salicylic acid was adopted into mainstream therapy but had the drawback of being a strong irritant to the stomach, though far more effective as an analgesic & anti-platelet agent than the crude original. (Note: Had these scientists studied salicin instead, they would have found that nature had already designed a substance with a good yield of salicylic acid that was also kind to the stomach too!).

In the plant, salicylates act as a phytohormone involved in plant growth & development, photosynthesis, transpiration, ion uptake and transport, and the endogenous signaling involved in mediating the plants’ defense against pathogens by inducing the production of pathogenesis-related proteins. These signals can also move to nearby plants by being converted to the volatile ester, methyl salicylate, providing mutual immune support within the forest.

In the body, Salicin is converted into Salicylic acid and is used primarily as an analgesic, anti-inflammatory and anti-rheumatic agent. It is also a key ingredient in many skin care products as a keratolytic and comedolytic agent by causing the cells of the epidermis to shed more readily, opening clogged pores and neutralizing bacteria within, preventing pores from clogging up again by constricting pore diameter, and allowing room for new cell growth.

In general the action of salicylates are:

• Anti-inflammatory
• Analgesic
• Antipyretic
• Antiseptic
• Keratolytic & Comedolytic
• Note: Salicin does not demonstrate the antiplatelet effect seen with aspirin

It should be noted that salicylate-rich plants have been used traditionally and with good results for pain and inflammation, however their analgesic actions are typically slow-acting but longer lasting (won’t work fast like aspirin can for a headache).

The Pharmacology of Salicylates

Salicin derivatives are absorbed in the small intestine or carried to the distal ileum & colon where gut flora convert this glycoside into its aglycone, salicylic alcohol, via partial fermentation. The salicylic alcohol is then absorbed and oxidized in the blood, tissues, and liver to give salicylic acid, which is the main and most active form. Despite the elaborate route by which salicin delivers salicylic acid into the blood stream, the relative bioavailability and conversion of salicin to salicylic acid is relatively rapid (< 1 hour).

From studies conducted so far, salicin exerts effects on several pro-inflammatory targets including cyclo-oxygenase enzymes 1 & 2, and has been shown to produce significant inhibition of TNF-alpha and NF-K-beta.

To Summarize:

• Salicin is converted in the body into salicylic acid, which interacts with the enzymes that mediate inflammation.
• When salicin reaches the distal ileum or colon, bacterial gut flora digest salicin into salicyl alcohol & glucose
• Conversion of salicyl alcohol to salicylic acid occurs preferentially in areas of higher acidity in the blood and body tissues

Toxicity & Adverse Effects

• In high doses salicylic acid has an ototoxic effect by inhibiting prestin, which is the motor protein of the outer hair cells of the inner ear of the mammalian cochlea. It has been known to induce transient hearing loss in zinc-deficient individuals.
• Theoretically Salicylism which is an acute overdose of salicylates can produce toxicity symptoms ranging from mild nausea, vomiting, abdominal pain, lethargy, tinnitus, and dizziness, depending on the dose consumed.

Herbal Examples

• Salix sp. (Willow)
• Poplar sp.  (Poplar)
• Filipendula ulmaria (Meadowsweet)
• Viburnum opulus (Cramp bark)
• Viburnum prunifolium (Black Haw)
• Gaultheria procumbens (Wintergreen)