<jats:p>The antiinflammatory principle of the brown alga Caulocystis cephalornithos has been shown to be 6-tridecylsalicylic acid. Four other metabolites, 3-tridecylphenol, pentadec-1-ene, (E)-heptadec-3-en- 2-one and 8-hydroxy-3-undecyl-1H-2-benzopyran-1-one were also isolated from the dichloromethane extract of the freeze-dried alga.