Trihydroxyflavones from Scutellaria baicalensis: Separation by a Facile MEKC Technique and Comparison to an Analytical HPLC Method

Abstract

Phenolic were extracted from the roots of Scutellaria baicalensis Georgi (Labiatae) using methanol. The phenolics of the crude extract were examined by high‐performance liquid chromatography (HPLC) using an analytical C18 column coupled with ultraviolet‐diode array detection (UV‐DAD). Chromatograms were compared with those acquired by micellar electrokinetic chromatography (MEKC) with UV‐DAD. A good separation of the phenolics from the crude extract was achieved by the electrophoretic technique, and in a shorter time than by HPLC. Two dominant flavones, believed to be 5,6,7‐trihydroxyflavone and 5,6,7‐trihydroxyflavone‐7‐O‐β‐D‐glucopyranosiduronate, which are commonly referred to as baicalein and baicalin, respectively, were then isolated from the crude extract using a semi‐preparative HPLC method on a RP‐18 column. The identities of the separated trihydroxyflavones were confirmed by NMR spectroscopies and mass spectrometry as being baicalein (1) and baicalin (2). The employment of MEKC coupled with UV‐DAD as a technique to separate and to identify phenolic compounds, or their classes in natural products research, is expected to expand over the next decade.