Plicatic acid is a carboxylic acid from the resin acid group. It is naturally found in Thuja and cypress resin, and the main irritant and contact allergen present in thuja wood; in contrast to pine, where the primary irritant is abietic acid.

Plicatic acid
Names
IUPAC name
(7′β,8β,8′α)-3′,4,4′,8,8′,9-Hexahydroxy-5,5′-dimethoxy-2,7′-cyclolignan-9-oic acid
Systematic IUPAC name
(1S,2S,3R)-1-(3,4-Dihydroxy-5-methoxyphenyl)-2,3,7-trihydroxy-3-(hydroxymethyl)-6-methoxy-1,2,3,4-tetrahydronaphthalene-2-carboxylic acid
Identifiers
3D model (JSmol)
ChemSpider
UNII
  • InChI=1S/C20H22O10/c1-29-14-5-10-7-19(27,8-21)20(28,18(25)26)16(11(10)6-12(14)22)9-3-13(23)17(24)15(4-9)30-2/h3-6,16,21-24,27-28H,7-8H2,1-2H3,(H,25,26)/t16-,19+,20+/m0/s1 checkY
    Key: PGFBYAIGHPJFFJ-PWIZWCRZSA-N checkY
  • InChI=1/C20H22O10/c1-29-14-5-10-7-19(27,8-21)20(28,18(25)26)16(11(10)6-12(14)22)9-3-13(23)17(24)15(4-9)30-2/h3-6,16,21-24,27-28H,7-8H2,1-2H3,(H,25,26)/t16-,19+,20+/m0/s1
    Key: PGFBYAIGHPJFFJ-PWIZWCRZBT
  • O=C(O)[C@]2(O)[C@H](c1c(cc(OC)c(O)c1)C[C@@]2(O)CO)c3cc(O)c(O)c(OC)c3
Properties
C20H22O10
Molar mass 422.386 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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The highest concentrations of plicatic acid can be found in Thuja plicata (western red cedar), but Thuja occidentalis (eastern arborvitae) and Cryptomeria japonica (sugi) contain it in significant proportions as well.

Exposure to plicatic acid or Thuja wood dust can worsen asthma and provoke allergic reactions.[1]

References

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  1. ^ Ayars, GH; Altman, LC; Frazier, CE; Chi, EY (1989). "The toxicity of constituents of cedar and pine woods to pulmonary epithelium". The Journal of Allergy and Clinical Immunology. 83 (3): 610–8. doi:10.1016/0091-6749(89)90073-0. PMID 2926083.