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Abstract
  • Triterpenic acids (TA) are a structurally diverse class of triterpenoids and are widely distributed secondary metabolites in plants. The TA ursolic acid and oleanolic acid are known best and found in high concentrations in plants of the Rosaceae family - most prominently in apples. However, little information is available about the occurrence of TA in other Rosaceae species, despite the use of their fruits as food.In this thesis, a simple and efficient extraction strategy was developed for the isolation and purification of TA from Rosaceae fruits. The strategy involved the removal of water-soluble matrix compounds and the extraction of TA with ethyl acetate, achieving high extraction yields with up to >2 g TA/100 g dry apple peel, and high purity with up to 70 g TA/100 g extract. The protocol was optimized for application in educational institutions, including minimally equipped laboratories, and allowed the rapid extraction of TA within a few hours. Analytical methods based on gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID) were established for the quantitative and comprehensive analysis of TA patterns in Rosaceae fruits. Chromatographic separation in GC analyses was performed on a non-polar column and, in combination with the selection of specific fragment ions in MS detection, enabled the qualitative and quantitative analysis of more than 20 naturally occurring and modified TA derivatives. Quantification was carried out by external calibration with internal standards and validated regarding sensitivity, accuracy and precision.The analysis of quantitative TA patterns in 17 Rosaceae genera revealed high TA levels in edible fruits of the subfamily Amygdaloideae. In the food-related genera, the number of detected TA as well as their concentrations were lowest in Rubus and Fragaria and were highest in Malus. While no genus- or species-specific TA patterns were evident, the TA composition appeared to be stable within individual cultivars or varieties. These results highlight on the one hand the potential of Rosaceae fruits as a natural and sustainable source of TA and their nutritional relevance, and on the other hand their role in improving the chemotaxonomic differentiation of Rosaceae cultivars.
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