Definition of usnic acid in US English:

usnic acid


  • A yellow crystalline compound which is present in many lichens and is used as an antibiotic.

    A tricyclic phenol; chemical formula: C₁₈H₁₆O₇

    • ‘Bitter orange, aristolochic acid and usnic acid are all used for weight loss.’
    • ‘I don't know anyone else who's working on the toxicity of usnic acid besides me.’
    • ‘Although several synthetic compounds inhibit this key pigment enzyme, the scientists found that usnic acid was over 10 times more effective than others tested.’


Mid 19th century: usnic from medieval Latin usnea (from Arabic ushnah ‘moss’) + -ic.


usnic acid

/ˌəsnik ˈasid/