A New VHR Dual-Specificity Protein Tyrosine Phosphatase Inhibitor fromDendrobium moniliforme

Bioassay-guided fractionation of the EtOAc-soluble extract of Dendrobium moniliforme afforded a new phenanthraquinone-type metabolite, 7-hydroxy-5,6-dimethoxy-1,4-phenanthrenequinone ( 1), along with the previously reported 5-hydroxy-3,7-dimethoxy-1,4-phenanthrenequinone ( 2). The structures of the compounds were identified mainly on the basis of MS and NMR data. Compound 1 inhibited VHR dual-specificity protein tyrosine phosphatase (DS-PTPase) activity in a dose-dependent manner, displaying an IC (50) value of 3.0 +/- 0.2 microM.