Analysis and stability of the constituents of Curcuma longa and Harpagophytum procumbens tinctures by HPLC-DAD and HPLC–ESI-MS

In the present study two methods based on liquid chromatography with diode array detection (HPLC-DAD) coupled to an electrospray ionisation (ESI-MS) interface were developed for the determination of constituents in the tinctures (60%, v/v, DER 1:5) of turmeric (Curcuma longa L.) and Devil's claw (Harpagophytum procumbens L.). The developed simple and effective assays permitted the quality control of both tinctures. The aim of this work was to assess the qualitative and quantitative profile of the constituents of two widely marketed commercial preparations and to evaluate chemical stability of their marker constituents during accelerated thermal stability test by HPLC analysis. Characteristic constituents of C. longa rhizomes are the curcuminoids, whereas characteristic constituents of H. procumbens are acylated iridoid glycosides and phenylethylalcohols. Constituents of Devil's claw tincture (mainly iridoids) were more stable than curcuminoids of turmeric.