Graphene Oxide Nanoparticle-Assisted Promotion of Stevioside, Rebaudioside A, and Selected Biochemical Attributes in Stevia rebaudiana Bertoni.

Stevia rebaudiana Bert. is commonly known as candy leaf, sugar leaf, or sweet leaf. It is a natural sweetener that has low calories and is used as a substitute for sucrose. The objective of this research is to evaluate the effects of graphene oxide (GO) on the growth, biochemical activities, and stevioside and rebaudioside A production of Stevia in in vitro-raised plantlets. For this, green nanomaterials of GO (0, 2, 4, 6, 8, and 10 mgL^-1) were applied to the in vitro plants to enhance its sweetness by triggering the production of stevioside and rebaudioside A and other growth and biochemical parameters. It was observed that all the growth parameters of Stevia plants significantly increased with all GO treatments tested. Total chlorophyll and protein contents were increased (1.85- and 2.65-fold increase from the control) by applying 8 mgL^-1 of GO to the MS medium. The maximum value (4 mg·g^-1 of protein) of peroxidase activity (POD) was observed by applying 4 mgL^-1 of GO, 28.92-fold increase from the control. In comparison, superoxide dismutase activity (SOD) (0.4 mg·g^-1 protein) was observed with 10 mgL^-1 of GO (1.56-fold increase from the control). Stevioside (12.9 and 8.9 mg·g^-1 DW) and rebaudioside A (3.2 and 0.81 mg·g^-1 DW) were observed only at 6 and 8 mg·L^-1 treatment of graphene oxide. According to the findings, using graphene oxide (GO) had a significant impact on the growth, biochemical activities, and steviol glycoside production in Stevia. This shows that GO has the potential to be a valuable enhancer of sweetness and overall Stevia leaf quality, providing great prospects for the development of low-calorie natural sweeteners.