Application of HPTLC-MS for the on-line identification of oxypregnan glycosides in Hoodia gordonii

Hoodia gordonii (Mass.) Sweet is a succulent plant from South Africa and Namibia which has been used by the indigenous people to suppress appetite. Oxypregnan glycosides (hoodigosides) are considered as active principles [1]. HPLTC methods have been previously developed for the fingerprint analysis and identification of extracts from Hoodia gordonii [2,3]. Ion-trap tandem mass spectrometry and liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry have been used for the identification of isolated steroidal glycosides in Hoodia gordonii [4].

Recently, an HPTLC-MS Interface became available, which semi-automatically can extract zones of interest directly from a TLC/HPTLC plate and can direct them into a LC-MS system so that mass spectra can be obtained [5,6]. Previously we have tested the HPTLC-MS Interface for analysis of flavonoid containing herbal drugs [7]. We now have investigated the HPTLC-MS Interface for the identification of hoodigosides in extracts of Hoodia gordonii. Extracts have been applied as bands onto HPTLC plates using an automatic TLC sampler. Separated zones were eluted from the plate by the HPTLC-MS interface using methanol as solvent delivered by an HPLC pump at 100µl/min. The interface was hyphenated to a Finnigan LCQ Deca XP Plus ion trap mass spectrometer equipped with an electro spray ionization (ESI) source. Hoodigosides M, L, U, O, E, F, J, N, and C could be identified on the basis of the mass spectra obtained by HPTLC-MS. Therefore, the HPTLC-MS interface is a quick and powerful tool for the on-line identification of hoodigosides in TLC separations and can complement the classical TLC detection tools.

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