Analysis of fresh triterpenoid resins and aged triterpenoid varnishes by high-performance liquid chromatography–atmospheric pressure chemical ionisation (tandem) mass spectrometry

Abstract

Fresh triterpenoid (dammar and mastic) resins and aged triterpenoid varnishes were analysed by on-line HPLC–MS using atmospheric pressure chemical ionisation (APCI). Twenty components were identified in the fresh resins [dammarenolic acid, ursonic acid, oleanonic acid, hydroxydammarenone (I and II), dammaradienol, oleanonic aldehyde, dammarenediol, ursonic aldehyde, oleanolic aldehyde, ursolic aldehyde, hydroxyhopanone, dammaradienone, moronic acid, (3 l,8 R)-3,8-dihydroxypolypoda-13 E,17 E,21-triene, (8 R)-3-oxo-8-hydroxypolypoda-13 E,17 E,21-triene, masticadienonic acid, isomasticadienonic acid, 3- O-acetyl-3-epimasticadienolic acid and 3- O-acetyl-3-epiisomasticadienolic acid]. Analysis of the aged varnishes revealed the presence of some oxidised triterpenoid components [11-oxo-oleanonic acid, 11-oxo-oleanonic acid, 3-oxo-25,26,27-trinordammarano-24,20-lactone, 20,24-epoxy-25-hydroxy-3,4-seco-4(28)dammaren-3-oic acid and some ocotillone type molecules]. Most constituents of these complex samples were well resolved by reversed-phase HPLC. APCI-MS provides useful information about the molecular mass and the presence of certain functional groups. Specific marker compounds were found, which enable the discrimination between aged dammar and mastic varnishes by HPLC–APCI-MS. The fragmentation behaviour of triterpenoids under APCI conditions was compared to that under electron impact conditions. Mass spectrometric fragmentation of triterpenoids with a saturated ring system is straightforward. Triterpenoids with an unsaturation in the ring system probably give rise to double bond migration. Subsequent low energy MS–MS analysis does not provide more structural information, since mainly non-specific ring fragment ions are formed.