Micellar electrokinetic chromatography of the constituents in Philippine lagundi (Vitex negundo) herbal products

Vitex negundo or lagundi is an important herbal medicine in Asia and various commercial products of this herb's leaves have been flooding the market. Reports on the chemical constituents of such products were limited and directed to only one selected chemical marker. Here, micellar electrokinetic chromatography using a fused silica capillary was used for analysis of the methanolic extract of Philippine lagundi herbal products. The separation solution, injection, and separation voltage was 50 mM SDS with 50 mM phosphoric acid at pH 2.5, 6 s at 25 mbar, and 20 kV at negative polarity, respectively. With UV detection at 200 nm, the LODs (S/N = 3) were in the sub-μg/mL range which were sufficient for detection without the need for on-line or off-line sample concentration. The repeatability values were all below 3.9% for migration time and peak signals. When the method was used to real samples, a flavonoid (isoorientin) and two iridoid glycosides (agnuside and negundoside) were identified as the target chemical markers within a 12 min electrophoretic run. The accuracy was from 95% to 129%. The results also suggested that agnuside was the major component in Philippine lagundi. The method was simple, effective, low cost, and can be used for authenticity evaluation of lagundi products.