Türkiye’deki Bazı Polygala L. (Polygalaceae) Taksonlarının Fitokimyası ve Kemotaksonomisi

Abstract

In this thesis, it is aimed to reveal the phytochemistry and chemotaxonomy of some Polygala L. (Polygalaceae) taxa in Turkey. The genus is represented by 17 native and one cultivated species in Turkey. Five of these taxa are endemic. Phytochemical studies have been performed on the roots of P. azizsancarii and whole plant of P. inexpectata, both of which are narrow endemic species. Various compounds were isolated from the methanol extracts of the plants by using different chromatographic techniques. The structures of the isolated compounds were then determined by spectroscopic methods, including 1D-NMR (1H NMR, 13C NMR, DEPT-135), 2D-NMR (COSY, NOESY, HSQC, HMBC), INADEQUATE, HRMS and X-ray crystallographic studies. In total, 19 compounds were isolated. Based on the available spectroscopic data, the structures of 19 compounds were established as two previously undescribed xanthones; 3-O-β-D-glucopyranosyloxy-1,6-dihydroxy-2,5,7-trimethoxyxanthone (or sancaroside A) and 3-O-β-D-glucopyranosyloxy-1,6-dihydroxy-2,7-dimethoxyxanthone (or sancaroside B); seven previously described xanthones, one lignan, one flavone glycoside, and nine sucrose esters. Metabolomic profiling of the plants was performed using an LC-qTOF-MS system. Isolated compounds, four reference compounds (namely hederagenin, polygalaksanton III, tenuifolin, and senegenin) and the compounds found in the device library were all included during inter-taxa screening. The metabolomic fingerprints of the plant species belonging to nine different taxa were subsequently classified by multivariate data analysis. The principal component analysis (PCA) yielded both similar and different metabolomic profiles between taxa. Considering the PCA analysis results, P. supina and P. pruinosa were distinguished from other taxa by having similar chemicals, while P. venulosa and P. major had similar chemicals. P. inexpectata, however, was shown to have a different chemical content from all other taxa. In addition, an inter-taxa chemotaxonomic approach was implemented according to the K-Means clustering method by including the isolated chemicals and four references. The optimum clustering of Polygala taxa was estimated to be two by using the base packages in the R studio environment. It was observed that P. turcica represented the transition between the botanical groups. In a group of taxa that were divided into two with P. turcica in terms of chemical content, P. supina, P. pruinosa and P. inexpectata constituted one group, while P. papilionacea, P. vulgaris, P. venulosa, P. major and P. monspeliaca constituted the other group. The determining chemicals in our analyses were identified as 3'-O-feruloyl-sucrose (or sibiricose A5), 3'-O-(sinapoyl)-sucrose, 6-O-sinapoyl, 3'-O-trimethoxy-cinnamoyl-sucrose (or tenuifoliside C), 3-O-β-D-glucopyranosyloxy-1,6-dihydroxy-2,5,7-trimethoxyxantone (or sancaroside A) and 1,3,6-trihydroxy-2,5,7-trimethoxyxantone. In conclusion, the results of the first PCA analysis and the results obtained by the K-Means clustering method are mostly in agreement.