Anti-Inflammatory Activity of Aspirin - It's All About Salicylic Acid

A recent article published in the Journal of Agricultural and Food Chemistry suggests that the naturally occurring plant chemical, salicylic acid, may also occur naturally in animals, including humans.1 According to the authors, salicylic acid is "likely to become increasingly recognized as an animal bioregulator, perhaps in a class of its own."

While we've just begun to realize the importance of endogenous salicylic acid in humans, plant-derived or synthetic forms of salicylic acid have been used for centuries to treat pain, fever, and inflammation. In 1900, the German pharmaceutical company, Bayer AG, patented an acetylated form of salicylic acid known as acetylsalicylic acid, or aspirin.2

 

Name CAS Registry Number®
salicylic acid 69-72-7
acetylsalicylic acid 50-78-2

Even with such a long history of use, we have yet to uncover all there is to know about the anti-inflammatory activity of salicylic acid and aspirin. Information in the CAS databases details what we have learned from the last few decades of research. For example, John R. Vane reported in 1971 that aspirin's anti-inflammatory activity was due to its ability to inhibit the production of pro-inflammatory prostaglandins, including prostaglandin (PG) E2 (CAS Registry Number 363-24-6).3 Vane and others later reported that this inhibition depended on aspirin first being de-acetylated to salicylic acid:

  • "We conclude that the anti-inflammatory action of both drugs depends on the inhibition of PGE2 synthesis by salicylate."4

In addition to explaining why aspirin and salicylic acid have similar anti-inflammatory activity, Vane's work confirmed the 1899 claim by Bayer scientist Heinrich Dreser that aspirin is no more than a pro-drug for salicylic acid.5

Despite the evidence, aspirin's specific mechanism of action was later attributed to its unique ability to acetylate cyclooxygenase (COX) enzymes involved in prostaglandin biosynthesis - a premise that ignores the fact that salicylic acid does not have the capacity to acetylate.  A more likely mechanism for the inhibition of prostaglandin biosynthesis by salicylic acid and aspirin is described in an article published in 1999:

The authors suggest that salicylic acid and aspirin block prostaglandin production not by inhibiting cyclooxygenase enzyme activity but by inhibiting upstream expression of cyclooxygenase genes.

You can use SciFinder® or STN® to search the CAS databases for additional information about salicylic acid, aspirin, prostaglandins, and cyclooxygenase enzymes.  If your organization is enabled to use the web version of SciFinder, you can directly access details for the substances and references listed in this article.

Contributed by
Peter S. Carlton, Ph.D.
CAS Communications


References
  1. Paterson, J.R.; Baxter, G.; Dreyer, J.S.; Halket, J.M.; Flynn, R.; Lawrence, J.R. Salicylic Acid sans Aspirin in Animals and Man: Persistence in Fasting and Biosynthesis from Benzoic Acid. J. Agric. Food Chem. 2008, 56, 11648-11652.
  2. Hoffmann, F. Acetyl Salicylic Acid. U.S. Patent 644,077, Feb 27, 1900.
  3. Vane, J.R. Inhibition of Prostaglandin Synthesis as a Mechanism of Action for Aspirin-like Drugs. Nat. New Biol. 1971, 231, 232-235.
  4. Higgs, G.A.; Salmon, J.A.; Henderson, B.; Vane, J.R. Pharmacokinetics of Aspirin and Salicylate in Relation to Inhibition of Arachidonate Cyclooxygenase and Antiinflammatory Activity. Proc. Natl. Acad. Sci. USA 1987, 84, 1417-1420.
  5. Dreser, H. Pharmacological One on Aspirin (Acetylsalicylic Acid). Pflugers Arch. 1899, 76, 306-318.

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