Ratanhiaphenol III from Ratanhiae radix is a PTP1B inhibitor.

The inhibition of protein tyrosine phosphatase 1B (PTP1B) is considered a valid strategy to combat insulin resistance and type II diabetes. We show here that a dichloromethane extract of Ratanhiae radix ( RR_EX) dose-dependently inhibits human recombinant PTP1B in vitro and enhances insulin-stimulated glucose uptake in murine myocytes. By determination of the PTP1B inhibiting potential of 11 recently isolated lignan derivatives from RR_EX, the observed activity of the extract could be partly assigned to ratanhiaphenol III. This compound inhibited PTP1B in vitro with an IC (50) of 20.2 µM and dose-dependently increased insulin receptor phosphorylation as well as insulin-stimulated glucose uptake in cultured myotubes. This is the first report to reveal an antidiabetic potential for a constituent of rhatany root, traditionally used against inflammatory disorders, by showing its capability of inhibiting PTP1B.