Identification of the major compounds in extracts of Verbena officinalis L. (Verbenaceae) by HPLC with post-column derivatization

A qualitative reversed-phase HPLC method has been developed for the analysis of 50 % MeOH extracts of Verbena officinalis L. (Verbenaceae) leaves. The method enables separation of the main constituents: iridoids, flavonoids and phenolic acid derivatives. Simultaneous detection at different wavelengths, measurement of the UV spectrum of each separated compound during elution and co-injection of reference substances facilitated easy and rapid identification of verbenalin, hastatoside and verbascoside. As some of these compounds, mainly flavonoids, have closely related structures, however, characterization by derivatization with reagents inducing a shift of UV absorption maxima was required. This furnished additional structural information. The reagents were adapted for compatibility with the solvent system used for the chromatographic separation.