Eumitrin L: a new xanthone dimer from the lichen Usnea baileyi

Area of Science:

• Natural Product Chemistry
• Lichenology
• Pharmacognosy

Background:

• Lichens are a rich source of diverse secondary metabolites.
• Usnea baileyi is a lichen species known for its potential chemical constituents.

Purpose of the Study:

• To isolate and characterize new and known compounds from the lichen U. baileyi.
• To evaluate the isolated compounds for tyrosinase inhibitory and antioxidant activities.

Main Methods:

• Compound isolation using column chromatography.
• Structural elucidation via spectroscopic analyses (1D, 2D NMR, DP4, ECD).
• Bioactivity assays including tyrosinase inhibition and DPPH radical scavenging.
• Molecular docking simulations.

Main Results:

• Isolation of a new dimeric xanthone, Eumitrin L, and 13 known compounds.
• Compounds 6, 7, 8, 11 demonstrated tyrosinase inhibition.
• Compounds 3, 10, 13, 14 exhibited significant antioxidant properties.
• Protocetraric acid (6) and usnic acid (10) were identified as the most active compounds.

Conclusions:

• The lichen U. baileyi produces compounds with notable biological activities.
• Eumitrin L represents a novel dimeric xanthone.
• Protocetraric acid and usnic acid show promise as natural tyrosinase inhibitors and antioxidants.