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 (C-18 RP) thin-layer chromatography (TLC) and C-18 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 C-18 RP-HPTLC plates. Cycloartenol could be separated from related compounds only on C-18 RP-TLC but not on the C-18 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 C-18 RP be performed before HPLC analysis. (C) 2009 Elsevier B.V. All rights reserved.