CAS 125-46-2PubChem CID 5646
Usnic Acid
Usnic acid is a furandione found uniquely in lichen that is used widely in cosmetics, deodorants, toothpaste and medicinal creams as well as some herbal products. Taken orally, usnic acid can be toxic and has been linked to instances of clinically apparent, acute liver injury. — LiverTox
- IUPAC name
- 2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyldibenzofuran-1,3-dione
- Molecular formula
- C18H16O7
- Molecular weight
- 344.3 g/mol
- Exact mass
- 344.08960285 Da
- XLogP3
- 1.4
- Topological polar surface area
- 118.0 Ų
- Hydrogen-bond donors
- 2
- Hydrogen-bond acceptors
- 7
- Covalent units
- 1
- Defined stereocentres
- 0
Also known as
UsniacinUsnoUsninic acid1,3(2H,9bH)-Dibenzofurandione, 2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-2,6-Diacetyl-7,9-dihydroxy-8,9b-dimethyl-1,3(2H,9bH)-dibenzofurandione0W584PFJ77NSC-85171,3-(2H,9bH)-Dibenzofurandione, 2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-
16 more reported names
RefChem:901508204-740-72,6-diacetyl-3,7,9-trihydroxy-8,9b-dimethyldibenzofuran-1-oneCHEBI:38319UsneinUsnicAcidUsninsaeure7-Hydroxy-(S)-usnateusnic-acidL-Usnic acidNSC 85172,6-Diacetyl-7,9-dihydroxy-8,9b-dimethyldibenzo[b,d]furan-1,3(2H,9bh)-dioneNSC5890NSC8517(+/-)-Usnic acidNSC5889
External database identifiers
- ChEBI:CHEBI:2264
- ChEMBL:CHEMBL1375951
- EPA DTXSID:DTXSID0040123
- PubMed:38724177
- PubMed:37840363
- PubMed:32508146
- PubMed:31715134
- PubMed:27497765
- PubMed:27369375
- PubMed:25870318
- PubMed:25078063
- PubMed:23686521
- PubMed:23422721
- PubMed:23099095
- PubMed:22777745
Evidence from additional scientific databases
NIH PubChem PUG-View
Exact identifier match5646
Attributed physical-property, hazard, environmental and use annotations.
- Color/Form: ... yellowish /colored/ pigment. Source: Hazardous Substances Data Bank (HSDB)
- Color/Form: Yellow orthorombic prisms from acetone Source: Hazardous Substances Data Bank (HSDB)
- Color/Form: Crystalline yellow solid Source: Hazardous Substances Data Bank (HSDB)
- LogP: log Kow = 2.88 Source: Hazardous Substances Data Bank (HSDB)
- Melting Point: 204 °C Source: Hazardous Substances Data Bank (HSDB)
- Physical Description: Yellow solid; [Merck Index] Yellow crystalline solid; [MSDSonline] Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
- Solubility: Solubility at 25 °C (g/100 ml): acetone, 0.77; ethyl acetate, 0.88; fural, 7.32; furfuryl alcohol, 1.21 Source: Hazardous Substances Data Bank (HSDB)
- Solubility: Solubility at 25 °C (g/100 ml): water, <0.01 Source: Hazardous Substances Data Bank (HSDB)
- Signal: Danger Source: European Chemicals Agency (ECHA)
- GHS Hazard Statements: H301 (70.2%): Toxic if swallowed [Danger Acute toxicity, oral]; H302 (29.8%): Harmful if swallowed [Warning Acute toxicity, oral]; H400 (70.2%): Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard]; H410 (70.2%): Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard] Source: European Chemicals Agency (ECHA)
- Precautionary Statement Codes: P264, P270, P273, P301+P316, P301+P317, P321, P330, P391, P405, and P501 (click each P-code to see the statement) Source: European Chemicals Agency (ECHA)
- ECHA C&L Notifications Summary: Aggregated GHS information provided per 94 reports by companies from 5 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.; Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown. For more detailed information, please visit ECHA C&L website. Source: European Chemicals Agency (ECHA)
- Sources/Uses: Antibacterial compound present in lichens; [Merck Index] Used as preservative and antibiotic (folk remedy); [HSDB] Used as a topical antibiotic; Workers exposed to lichens (forestry and horticulture) may develop allergic contact dermatitis. [Kanerva, p. 1845] Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
- Activities with risk of exposure: Ingesting herbal remedies [Category: Food & Drugs] Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
- Uses: Medicine: antibiotic /SRP: folk remedy/ Source: Hazardous Substances Data Bank (HSDB)
- Uses: Preservative Source: Hazardous Substances Data Bank (HSDB)
- Uses: Usnic acid is effective in vitro against ...anerobic bacteria. Source: Hazardous Substances Data Bank (HSDB)
Mapped by: Existing checksum-valid CAS to unique PubChem CID match. Retrieved: 2026-08-31. Open source record
Scientific classifications and hazard annotations provide context and do not replace the market-specific regulatory decision shown above.
Additional source coverage and match status
| Source | Result | Checked |
|---|---|---|
| NIH PubChem PUG-View | Exact match | 2026-08-31 |
A recorded no-match is useful evidence that the source was checked; it is not a claim that the substance does not exist elsewhere.
Retrieved from NIH PubChem on 2026-09-02 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.