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 GABA(A) receptor: wogonin (K-i = 2.03 +/- 0.24 mu M), baicalin (K-i = 77.10 +/- 4.79 mu M), baicalein (K-i = 5.69 +/- 0.95 mu M), and scutellarein (K-i = 12.00 +/- 1.27 mu M) 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.