Pharmacognosic researches on some Scorzonera L. species growing in Turkey

Isolation of natural compounds and elucidation of their structures is significant in the scientific process due to the potential of being a new drug-active ingredient. Scorzonera L. species are known to be consumed as vegetables in the world and Turkey and used in traditional medicine. There are approximately 180 species of the Scorzonera genus worldwide and 52 species, 31 of which are endemic in Turkey. Literature survey resulted that no biochemical and phytochemical research has been done on Scorzonera aucheriana and Scorzonera coriacea plants which are endemic to Turkey. Therefore, phytochemical studies of these plant were chosen as Ph.D. thesis. Crude methanol extract from the aerial parts of plants were obtained then fractionated with n-hexane, chloroform, ethyl acetate, and water. Antioxidant effect (DPPH and FRAP), total phenolic substance and total flavonoid were determined from the crude extracts and fractions. And also, antimicrobial activities (three grams (+), three grams (-), one gram, and two fungi) of crude extracts/fractions were investigated. Isolation and purification were carried out on the fractions of S. aucheriana using various chromatographic methods, and a total of 22 compounds were isolated. Characterization of isolated compounds were carried out using advanced spectroscopic methods. Among them, twelve compounds were new (scorzoaucerioside I-V, iso-scorzopygmecoside, scorzonerenon, scorzoaucerin A-D and taraxasterol oleate) and ten of them were known compounds (astragalin, scorzopygmecoside, scorzocreticoside II, scorzocretisin, 3,5-O-dicaffeoil-epi-quinic acid, 3,5-O-dicaffeoilquinic acid, ptiloepoxide, taraxasterol, lupeol, and β-sitosterol). All compounds were isolated for the first time from S. aucheriana. As a result of biological activity studies, among the fractions of S. aucheriana and S. coriacea, the best antioxidant activity was determined in the ethyl acetate fraction, and the strongest antimicrobial activity was found in the chloroform and ethyl acetate fractions. It has been determined that MIC values of scorzoaucerioside II-III, iso-scorzopygmecoside, and scorzoaucerin A within the range of 21.2-47.5 μg/mL and they showed selective anti-tuberculosis activity. In addition, it was determined that scorzonerenone was selective and effective against Pseudomonas aeruginosa strains at low doses (100 μg/mL). According to the DPPH and FRAP method, the iso-scorzopygmecoside showed the highest antioxidant activity.