Inhibitory activities of anthraquinones from Rubia akane on phosphatase regenerating liver-3.

The methanolic extract of the roots of Rubia akane (Rubiaceae) was found to show inhibitory activity on phosphatase of regenerating liver-3 (PRL-3). Bioassay-guided fractionation of the methanolic extract resulted in the isolation of two anthraquinone compounds, 2-methyl-1,3,6-trihydroxy-9,10-anthraquinone-3-O-(6'-O-acetyl)-α-rhamnosyl(1→2)-β-glucoside and 2-methyl-1,3,6-trihydroxy-9,10-anthraquinone, as inhibitors on PRL-3. These compounds inhibited PRL-3 in a dose-dependent manner with IC₅₀ values of 5.2 and 1.3 μg/mL, respectively.