Evaluation of new extraction approaches to obtain phenolic compound-rich extracts from Stevia rebaudiana Bertoni leaves

Microwave-assisted extraction (MAE) and pressurized liquid extraction (PLE) using food-grade solvents were applied to Stevia rebaudiana Bertoni leaves in order to obtain phenolic compound-rich extracts. The influence of various extraction parameters (i.e. solvent composition, temperature, time) on the total phenolic content was evaluated, reaching the highest phenol content (79 +/- 9 mg gallic acid equivalents/g dried leaves) with PLE using 50% aqueous ethanol at 200 degrees C. In addition, high-performance liquid chromatography coupled to electrospray ionization quadrupole-time of flight mass spectrometry was used to characterize the bioactive compounds in the richest extracts. A variety of phenolic compounds was identified, mainly phenolic acids and flavonoids, along with the diterpene glycosides responsible for the sweet taste. This study indicates that PLE represent a powerful tool to obtain Stevia extracts suitable for human consumption which can be used as source of antioxidant compounds and non caloric sweeteners.