Quality control studies and biological activity research on Stevia rebaudiana Bertoni leaves

Quality Control Studies and Biological Activity Research On Stevia rebaudiana Bertoni Leaves In this thesis, pharmacognosy research has been conducted on Stevia rebaudiana Bertoni, a South American originated plant that is native to Paraguay and Brazil. Quality control, quantitative analyses and biological activity researches were conducted on the leaves prepared from the plants cultivated in Turgutlu, Manisa of which the seeds were obtained from five different countries. Quality control and quantitative analyses were carried out based on the methods in European Pharmacopoeia. Loss on drying, total ash, ash insoluble in hydrochloric acid, determination of sulfate ash, determination of elemental content by X-ray fluorescence spectroscopy and quantitative determination of stevioside by high pressure liquid chromatography (HPLC) were conducted. Total phenolics and total flavonoid content were also determined. Antimicrobial and antioxidant activities were determined by microdiution method and DPPH radical scavenging capacity respectively. Keywords; Stevia rebaudiana Bertoni, stevioside, antioxidant, antimicrobial, HPLC, X-ray fluorescence spectroscopy