Protein tyrosine phosphatase 1B inhibitors from the root bark of Pseudolarix amabilis (Nelson) rehd. (pinaceae)

Abstract

Pseudolarix amabilis (Nelson) Rehd, is a monotypic genus plant belonging to the family Pinaceae. The root bark, known as “Tu-Jin-Pi” has been used for the treatment of skin diseases. During our activity screening, the water-soluble part of the 70% EtOH extract of P. amabilis bark showed excellent inhibitory bioactivities on PTP1B enzyme, leading to the phytochemical isolation of the root bark of P. amabilis. Three oleanane-type compounds (1-3) and seven phenolic compounds (4-10) were isolated, in which oleanolic acid 3-O-β-D-glucuronyl-6′-ethyl ester (1) was identified as a new saponin. The chemical structures of these compounds were elucidated by 1D/2D nuclear magnetic resonance and high resolution mass spectra. In addition, their pharmacological inhibitory bioactivities on PTP1B enzyme were evaluated, and the three oleanane-type compounds 1-3 exhibited inhibitory bioactivities with IC50 values of 1.90 ± 0.37, 19.15 ± 0.10 and 10.44 ± 0.59 μM, respectively.