[Phenolic constituents from lichen Usnea longissima]

Area of Science:

• Natural Product Chemistry
• Pharmacology
• Lichenology

Background:

• Lichens are a rich source of diverse secondary metabolites.
• Usnea longissima is a lichen species with potential for novel compound discovery.
• Investigating lichen metabolites is crucial for identifying new bioactive compounds.

Purpose of the Study:

• To isolate and identify chemical constituents from the lichen Usnea longissima.
• To evaluate the anti-inflammatory potential of the isolated compounds.
• To report novel natural products and compounds new to the Usneaceae family.

Main Methods:

• Extraction and isolation using various chromatographic techniques (silica gel, Sephadex LH-20, ODS, semi-preparative HPLC).
• Structure elucidation through comprehensive spectroscopic data analysis.
• In vitro anti-inflammatory assay measuring nitric oxide (NO) production in RAW 267.4 cells.

Main Results:

• Sixteen compounds were successfully isolated and identified.
• Useanol (1) was identified as a new natural product.
• Compounds 3, 4, 8, 10, 12, and 13 were reported for the first time from the Usneaceae family.
• Compounds 1, 8, and 13 exhibited significant anti-inflammatory activity with IC₅₀ values of 6.8, 3.9, and 4.8 μmol•L⁻¹, respectively, outperforming controls curcumin and indomethacin.

Conclusions:

• Usnea longissima is a valuable source of bioactive secondary metabolites.
• Compounds 1, 8, and 13 possess notable anti-inflammatory properties.
• Further research into these compounds may lead to the development of novel anti-inflammatory agents.