Planta Med. 2002 Dec; 68(12): 1063-5.

Inhibition of VHR dual-specificity protein tyrosine phosphatase activity by flavonoids isolated from Scutellaria baicalensis: structure-activity relationships.

Lee MS, Oh WK, Kim BY, Ahn SC, Kang DO, Sohn CB, Osada H, Ahn JS.

Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, South Korea.

Three flavonoids: norwogonin, dihydronorwogonin and baicalein, were isolated from the roots of Scutellaria baicalensis, as potential inhibitors of VHR dual-specificity protein tyrosine phosphatase (DS-PTPase). Norwogonin (IC 50 = 1.1 microM), dihydronorwogonin (IC 50 = 2.9 microM) and baicalein (IC 50 = 2.4 microM) showed potent inhibitory activity toward VHR, but had no inhibitory activity against T-cell protein tyrosine phosphatase or serine/threonine protein phosphatase 1. From comparisons to the inhibitory activities of other similar flavonoids, it could be suggested that the presence of a hydroxy group in the B ring of flavonoids interferes with the inhibitory activity toward VHR DS-PTPase.