Interaction of flavones from the roots of Scutellaria baicalensis with the benzodiazepine site.

A radioreceptor binding assay was used to guide the isolation of four chemical constituents in the organic solvent extracts of Scutellaria baicalensis Georgi capable of binding to the benzodiazepine site (BZD-S) of the GABAA receptor: wogonin (Ki = 2.03 +/- 0.24 microM), baicalin (Ki = 77.10 +/- 4.79 microM), baicalein (Ki = 5.69 +/- 0.95 microM), and scutellarein (Ki = 12.00 +/- 1.27 microM). All four compounds contain the flavonoid phenylbenzopyrone nucleus. Based on BZD-S binding, the order of affinity among these four compounds was wogonin > baicalein > scutellarein > baicalin.