ANTOXIDANT ACTIVITY AND PHENOLICS COMPOSITION IN STEVIA REBAUDIANA PLANTS OF DIFFERENT ORGIN

Abstract

The antioxidant activity and total phenolic contents in leaves and leaf extracts of Stevia plants grown under the different conditions of Egypt, India, Paraguay, Greece and Spain were studied. The moderate levels of total phenolics (from 5.64 to 6.45 mg mL-1) was found in Stevia leaf extracts from Egypt, India and Greece which can depend from the climate conditions during growing season of Stevia plants. High amounts of total phenolics contained leaves of Stevia plants from Paraguay and Spain (from 8.69 to 9.44 mg mL-1). The antioxidant activity in Stevia plants from Paraguay was about 46% and from Spain about 57%. The individual profile of phenolic acids differed between samples, Stevia leaf extracts from Greece, Spain and Paraguay has been shown the high contents of caffeic acid (29.9, 22.1 3 and 16.2 µM mL-1 respectively) and catechin (52.9, 64.2 and 48.1 µM mL-1) as compared to samples from Egypt and India. In these variants were present the high content of steviolbioside and RT 21 too. In same time another redistribution quantity of identified phenolics compounds in their composition compared with all experimental samples has been presented in the Stevia leaves from Greece. In leaf extract from Greece quantity of steviolbioside was less on 50% compared with variants of leaf extracts from India and Spain.