The Potential of Cold Plasma and Electromagnetic Field as Stimulators of Natural Sweeteners Biosynthesis in Stevia rebaudiana Bertoni.

Augustė Judickaitė,Irina Filatova,Veronika Lyushkevich,Vida Mildažienė,Rasa Žūkienė

doi:10.3390/plants11050611

Abstract

Stevioside (Stev) and rebaudioside A (RebA) are the most abundant steviol glycosides (SGs) responsible for the sweetness of Stevia rabaudiana Bertoni. As compared to Stev, RebA has a higher sweetening potency, better taste and therefore is the most preferred component of the stevia leaf extracts. The aim of this study was to determine the effect of pre-sowing seed treatment with abiotic stressors cold plasma (CP) and electromagnetic field (EMF) on the amount and ratio of RebA and Stev in the leaves of stevia. Additionally, the effect on total phenolic content, flavonoid content and antioxidant activity was investigated. Seeds were treated 5 and 7 min with cold plasma (CP5 and CP7 groups) and 10 min with electromagnetic field (EMF10 group) six days before sowing. The germination tests in vitro demonstrated that all treatments slightly increased germination rate and percentage. HPLC analysis revealed that CP and EMF had strong stimulating effect on SGs accumulation. All treatments increased RebA concentration approximately 1.6-fold; however, the ratio of RebA/Stev decreased from 8.5 in the control to 1.9, 2.5 and 1.1 in CP5, CP7 and EMF10 groups respectively, since the concentration of Stev increased more than RebA, 7.1, 4.6 and 11.0-fold, respectively, compared to control. However, treatments had opposite effect on total phenolic content, flavonoid content, and antioxidant activity. We have demonstrated for the first time that short time pre-sowing treatment of stevia seeds with CP and EMF can be a powerful tool for the enhancement of biosynthesis of RebA and Stev, however it can have negative impact on the content of other secondary metabolites.

Highlights

Publisher’s Note: MDPI stays neutralStevia rebaudiana Bert. (Bertoni) is a perennial shrub indigenous to Paraguay, SouthAmerica, and nowadays it is cultivated abundantly in many countries as economically important source of natural low-calorie sweeteners, steviol glycosides (SGs) [1]
We have reported for the first time that short time pre-sowing treatment of stevia seeds with cold plasma (CP) and electromagnetic field (EMF) can be a powerful tool for the enhancement of biosynthesis/accumulation of rebaudioside A (RebA)
Based on some our previous studies on different plant seeds [25,26,28,29], the chosen durations for seed treatments were 5 and 7 min for cold plasma, and 10 min for EMF treatment

Summary

Introduction

(Bertoni) is a perennial shrub indigenous to Paraguay, South. America, and nowadays it is cultivated abundantly in many countries as economically important source of natural low-calorie sweeteners, steviol glycosides (SGs) [1]. Steviabased sweeteners have increased in market usage due to growing consumer demand for natural products with low or no added sugars. There are at least 38 steviol glycosides identified in stevia to date [3]. Rebaudioside A (RebA) and stevioside (Stev) are the most abundant steviol glycosides (SGs) responsible for the sweetness of stevia (Figure 1). As compared to Stev, RebA has an additional glucose monomer that gives it a higher sweetening potency and RebA is the most preferred component of the stevia leaf extracts. Stev and RebA account for more than

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