Salicylic acid

August 25, 2015
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Salicylic acid (2-hydroxybenzoic acid) is a white solid first isolated from the bark of willow trees (Salix spp.), from which it gets its name. It also occurs as the free acid or its esters in many plant species.

In an early (1966) biosynthetic process, researchers at Kerr-McGee Oil Industries (now part of Andarko Petroleum) prepared salicylic acid via the microbial degradation of naphthalene. It is now commercially biosynthesized from phenylalanine.

Acetylsalicylic acid (aspirin), a prodrug to salicylic acid, is made by an entirely different process. Curiously, salicylic acid is also a metabolite of aspirin.

Salicylic acid and its esters are used as food preservatives, in skin-care products and other cosmetics, and in topical medicines. In 2015, J. L. Dangl, S. L. Lebeis, and co-workers at the University of North Carolina, Chapel Hill, discovered that native salicylic acid plays a role in determining which microbes are in the root microbiome of Arabidopsis thaliana, a weed that grows in Europe and Asia.

MOTW update:
November 4, 2024

Salicylic acid1 occurs naturally in willow trees and other plant species; and it is commercially biosynthesized from phenylalanine. It and its esters are used as food preservatives and in cosmetics and topical medicines. It is also a precursor of acetylsalicylic acid.

Beginning in the 2000s, salicylic acid and several other key chemicals stopped being produced in the United States because of low-priced competition from China. In October, Michael McCoy at C&EN reported on an initiative by the US Department of Defense to “reshore” 22 of these chemicals. Earlier this year, DOD funded Lacamas Laboratories (Portland, OR) to produce seven of the compounds, including salicylic acid. DOD has additional plans to reshore 28 more chemicals.

1. CAS Reg. No. 69-72-7.

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