Usimines A-C, Bioactive Usnic Acid Derivatives from the Antarctic Lichen Stereocaulon alpinum

Abstract

Usimines A-C (1？3), three new usnic acid derivatives, have been isolated from a MeOH extract of the Antarctic lichen Stereocaulon alpinum by various chromatographic methods. The structures of 1？3 were determined by analysis of their spectroscopic data (NMR, UV, MS) and by chemical methods. The known compound usnic acid (4) was also obtained. Compounds 1？4 showed moderate inhibitory activity against therapeutically targeted protein tyrosine phosphatase 1B (PTP1B).