Cold plasma (CP) induced secondary metabolites changes in Stevia rebaudiana Bertoni

Abstract

The most economically important source of natural low-calorie sweeteners, steviol glycosides (SGs) is Stevia rebaudiana Bertoni with stevioside (Stev) and rebaudioside A (RebA) being the most abundant. Pre-sowing seed treatment with cold plasma (CP) was shown to stimulate SGs biosythesis/accumulation up to several folds. In addition to SGs increase, the CP-induced increase of antioxidant activity was observed as well. This study aimed to evaluate the effect and it‘s universality of two types of CP on two different Stevia rebaudiana cultivars. The effect evaluted by comparing SGs, total flavonoid content (TFC), total phenolic content (TPC) and antioxidant activity (AA). Seeds of 2 stevia cultivars – SHUG A3-6 and SHUG HIGH A3 (HYBRID) – were treated for 2, 5 and 7 min. with two different CP equipment types – captively coupled (CC – CC2, CC5 and CC7 groups) and dieletric barrier discharge (DBD – DBD2, DBD5 and DBD7 groups) plasmas – before sowing. Both CC and DBD treatments stimulated SG production; however to different extents. In HYBRID CP5 induced the highest increase of 10% in RebA+ Stev concentration, in SHUG A3-6 the highest increase was observed in DBD5 group by 1.9 fold. The overall tendency to increase Stev and decrease RebA concentrations compared to control was observed in all groups. CP did not affect TFC and TPC except for SHUG A3-6 DBD5 group – where the increase in TPC concentration by 1.6 fold was observed. AA was stimulated in both cultivars by both plasmas. The highest AA increase was observed in DBD5 groups – by 1.7 fold in SHUG A3-6 and by 2.4 fold in HYBRID. In conclusion, seed treatment with two types of CP induced SGs concentration increase due to Stev biosynthesis stimulation which, in the case of DBD, correlated with the increase in antioxidant activity and TPC concentration rather than TFC in both cultivars. *The authors marked with an asterisk equally contributed to the work.