Enhancement of stevioside by abiotic elicitation in Stevia rebaudiana and upregulation of INS1, TRPM5, and GLP-1 in β-cells via plant extracts.

Stevia rebaudiana is an important source of steviol glycosides with antidiabetic properties. This study evaluated the effects of abiotic elicitors, including foliar application of 5% ethanol and root-zone excess iron (150 mg/L Fe; +Fe), on stevioside accumulation and the biological activity of leaf extracts in pancreatic β-cells. Ethanol treatment significantly stimulated vegetative growth, resulting in an approximately threefold increase in fresh biomass and a 62% enhancement in photosynthetic rate, without inducing oxidative stress. HPLC analysis demonstrated that stevioside content increased by 69% in ethanol-treated plants and by 104% under + Fe conditions, while rebaudioside A remained unchanged. In MIN-6 β-cells, ethanol-derived extracts upregulated INS1 expression by 3.11-fold at 12 h and triggered strong early activation of TRPM5 (20-fold at 2 h), followed by delayed GLP-1 induction. In contrast, +Fe extracts showed weaker effects on insulin-related genes. Overall, ethanol acts as an efficient elicitor enhancing stevioside biosynthesis and insulinotropic potential in vitro.