Abstract: The main crystalline princiiple "Baicalein" from the root of the Chinese drug Huang-Chin (Scutellaria baicalensis Georg.) of Labiatae has been proved to be effective in lowering blood pressure without any toxic effect, even when large doses are administered as shown by pharmacological and clinical tests The method for extracting, Baicalin has been improved, and as much as twothirds of the time required by the old procedure (Shibata et aL Acta Phytochim. (1922-23) I, 105) were saved by using the improved method. The maximum yield of the improved method could be as high as 5.4 per cent. A monomethyl ether of Baicalin was obtained by using the ordinary amount of diazomethane for methylation while a dimethyl ether was formed with an excess of the reagent. The following six derivatives have been prepared and all of them are considered as new compotmds. 1) 6-Methyl ether Baicalein methyl ester C₂₃H₂₂O₁₁, m.p. 218-220℃. 2) 5,6-Dimethyl ether Baicalein methyl ester C₂₄H₂₄H₂O, m.p. 198℃. 3) 6-Methyl ether Baicalein methyl ester tetra-acetate C₂₃H₁₈O₁₁ (COCH₃)₄,m.p. 190℃. 4) 5,6 Dimethyl ether Baicalein methyl ester tri-acetate C₂₄H₂₁O₁₁ (COCH₃)₃,m.p. 220℃. 5) 5,6-Dimethyl ether Baicalein C₁₇H₁₄O₅, m.p. 209--208℃. 6) 5,6-Dimethyl ether-7-acetyl Baioalein C₁₉H₁₆O₆, m.p. 156--158℃. (m.p. are uncorrected)