APPROACH TO STEVIA STANDARDIZATION AS PERSPECTIVE MEDICINAL PLANT: EVALUATION OF STEVIA LEAVES FLAVONOID CONTENTS

Abstract

Stevia rebaudiana bertolli traditionally used as a sweetener has many pharmacological activities. The objects of the study were stevia leaves grown in the several districts of Russia. Together with sweet glycosides flavonoids can be a marker of stevia quality. Flavonoids from dry stevia leaves were extracted with ethanol-water solutions. The results show that the flavonoid content higher in 40 and 70% ethanol extracts. UV properties of stevia extracts were investigated. Absorption maxima at 300 and shoulder at 290 nm in stevia extracts are revealed. Chemical structures of stevia flavonoids are discussed. After adding aluminum chloride batochromic shifts in the spectra are observed. Complex of stevia flavonoids and AlCl3 had the maximum absorption at 403 nm. Aluminum chloride colorimetric assay were developed to evaluate total flavonoid contains in stevia extracts from the different Russian regions. Total flavonoid contents vary from 2 to 3 %. Maximum flavonoid content found in stevia leaves from the south of Russia.