Separation and identification of some common isomeric plant triterpenoids by thin-layer chromatography and high-performance liquid chromatography.

Chromatographic separation of 10 triterpenoids (alpha-amyrin, beta-amyrin, delta-amyrin, lupeol, lupenon, lupeol acetate, cycloartenol, cycloartenol acetate, ursolic acid, oleanolic acid) and 2 sterols (stigmasterol and beta-sitosterol) was studied. The chromatographic techniques included silica gel and reversed-phase (C18 RP) thin-layer chromatography (TLC) and C18 RP high-performance liquid chromatography (HPLC) using UV and mass spectrometric (MS) detection with atmospheric pressure chemical ionization (APCI). The TLC separation of the isomeric triterpenols lupeol, alpha-amyrin, beta-amyrin and cycloartenol was achieved for the first time using C18 RP-HPTLC plates. Cycloartenol could be separated from related compounds only on C18 RP-TLC but not on the C18 RP-HPLC. delta-Amyrin isolated from the tomato fruit surface extract could be separated from other amyrins only by HPLC. Tandem mass spectrometry allowed discrimination between the isomers lupeol, alpha-amyrin, beta-amyrin, delta-amyrin, cycloartenol and between lupeol acetate and cycloartenol acetate. The combination of 3 TLC methods and 2 HPLC methods enables qualitative determination of all 12 compounds and proves to be useful for the analysis of plant extracts. It is recommended that TLC screening on silica gel and C18 RP be performed before HPLC analysis.