Optimization of Eco-Friendly Extraction of Bioactive Compounds from Mentha spicata L. Using Ultrasound-Assisted Extraction Combined with Choline Chloride-Based Deep Eutectic Solvents

Abstract

Three choline chloride (ChCl)-based deep eutectic solvents (DESs) as a new type of green solvents were used for the ultrasound-assisted extraction (UAE) of bioactive compounds from Mentha spicata L. DES containing ChCl and malonic acid (MalA) was selected as the most promising, providing a more effective extraction of antioxidants from spearmint. Response surface methodology (RSM) and a Box-Behnken design (BBD) with three variables, ChCl:MalA molar ratio, water content (WC) in DES, and extraction time (t), were implemented for optimizing the extraction conditions. The optimal conditions were calculated to maximize the antioxidant capacity (AC) determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and cupric reducing antioxidant capacity (CUPRAC) assays, total phenolic acids (TPAc), total flavonoid aglycones (TFAgly), and total flavonoid glycosides (TFGly). The phenolic profiles in the obtained extracts were analyzed using ultra-performance liquid chromatography (UPLC), revealing that rosmarinic acid, ellagic acid, rutin, kaempferol, and kaempferol-3-O-rutinoside were predominant in the DES extracts.

Keywords: Antioxidant capacity; Extraction; Green solvents; Phenolic compounds; Response surface methodology; Spearmint; Ultra-performance liquid chromatography.