29 December 2008

Make some salicylic acid and call the doctor in the morning

John R. Paterson, Gwendoline Baxter, Jacob S. Dreyer, John M. Halket, Robert Flynn, James R. Lawrence (2008). Salicylic Acid sans Aspirin in Animals and Man: Persistence in Fasting and Biosynthesis from Benzoic Acid Journal of Agricultural and Food Chemistry, 56 (24), 11648-11652 DOI: 10.1021/jf800974z

Salicylic acid is a plant metabolite present in many plants, including rice, barley and soybean. Its functions in plants range from heat production to disease resistance (Raskin, 1992). In humans, it has fever and pain reducing effects. It is also the synthetic precursor of the drug aspirin, acetylsalicylic acid.

In this paper, Paterson et al. present several intriguing pieces of evidence on the presence of salicylic acid in the blood of various animals and humans. Among the more than 30 animals they tested, 2 birds, the burrowing owl and the Nene had the highest blood concentrations of salicylic acid (9.9 and 5.6 μmol/L, respectively). They were followed by both herbivorous and carnivorous species, including the Asian elephant (1.6 μmol/L), the Burmese python (1.4 μmol/L ) and the tiger (0.67 μmol/L). The only animals that had levels of salicylic acid below the limit of detection of the method used were 2 crustacean species that were also the only invertebrates in the list.

Likewise, vegetarian and nonvegetarian humans who had not recently consumed aspirin had overlapping ranges of blood salicylic acid levels and comparable median values of 0.11 and 0.07 μmol/L, respectively. In comparison, the median level of salicylic acid in the blood of aspirin users was 10 μmol/L. In addition, salicylic acid was found in the blood of 6 patients who had been fasting prior to abdominal surgical procedures.

Interestingly, in 2 groups of germ-free mice and rats serum salicylic acid levels were higher than those in control groups.

The authors conclude that humans not only obtain some salicylic acid from the foods they consume but that they also appear to synthesize it endogenously. One speculation presented in the paper is that salicylic acid, similar to its functions in plants, may also have defensive and regulatory roles in animals.

Raskin, I. Role of salicylic acid in plants. Annu. Rev. Plant Physiol. Plant Mol. Biol. 1992.43:439-463. pdf

1 comment:

thalarctos said...

This is very interesting--thank you for posting it, and bringing it to my attention.

I am currently trying to track down the accuracy of anecdotes I have heard regarding animals chewing on willow bark in a method consistent with using it to relieve pain. Whether or not any of the anecdotes are true, I cannot say, but the intersection of salicylic acid and animals is a very interesting topic.