PTP1B inhibitory secondary metabolites from the Antarctic lichen Lecidella carpathica

Abstract

Protein tyrosine phosphatase 1B (PTP1B) is an attractive therapeutic target for diabetes, playing a major role in negative regulation of the insulin signaling pathway. Bioassay-guided investigations of an MeOH extract of the Antarctic lichen, Lecidella carpathica, afforded three PTP1B inhibitory metabolites: hopane-6α,22-diol (1), brialmontin 1 (2), and atraric acid (3), along with two aromatic metabolites (4 and 5) previously isolated from a different Antarctic lichen species. Their structures were determined by analysis of NMR and MS data. Compounds 1？3 inhibited PTP1B activity in a dose-dependent manner with IC50 values of 3.7, 14.0 and 51.5 μM, respectively, and kinetic analyses of PTP1B inhibition by compounds 1 and 2 suggested that these compounds inhibit PTP1B activity in a competitive manner. In addition, 6,22-hopanediol (1) displayed some selectivity toward PTP1B over other protein tyrosine phosphatases, such as TCPTP (IC50 = 8.4 μM), SHP-2 (IC50 > 68 μM), LAR (IC50 > 68 μM), and CD45 (IC50 > 68 μM).