Hande Karaköse

• Stevia rebaudiana (Bertoni) is from the Asteraceae family of plants with significant economic value due to its high content of natural zero calorie steviol glycoside sweeteners in its leaves. The leaves contain ent-kaurene glycosides, comprising stevioside, rebaudioside A, B, C, D, E, F and dulcoside A. Rebaudioside A and stevioside are the most abundant diterpene glycosides (steviol glycosides) in the leaves. The phytochemical characterization of stevia leaves is playing an important role in a future EU consumption of stevia as a novel food. For this purpose, the chemical composition of stevia (phenols and steviol glycosides detailed, with lipids and proteins in representative cases) was studied and methods have been developed for quantitative and qualitative analysis. Stevia leaves cultivated in more than ten locations inside and outside of Europe with seven different varieties, corresponding to total of 166 stevia samples, were extracted and their chemical composition was profiled and quantified by LC-MS for steviol glycosides and polyphenols (chlorogenic acids and flavonoids). Profiling, identification and quantification of terpenoids and lipids were achieved by using GC, GC-MS and MALDI-TOF techniques. In addition, protein extraction and analysis was carried out to identify potentially allergenic proteins in stevia leaves. Protein separation and isolation was achieved with 2-dimensional electrophoresis (2DE) and MALDI-TOF MS analysis was performed for the identification of individual proteins. Furthermore, as stevia may cultivated within various regions of the EU with different soil and climatic conditions it is important to know whether an EU-common specification will be achieved and how stevia leaves from regions outside EU can be distinguished on a scientific basis. For this purpose, principal component analysis (PCA) was performed based on the LC-MS dataset of stevia phenols. In addition, effect of growth origin and variety on stevia secondary metabolite profile was analyzed statistically by ANOVA (analysis of variance).