Food-grade deep eutectic solvent extraction of antioxidant polyphenols from peppermint (Mentha × piperita L.): Screening, optimization and metabolite profile

Abstract

Peppermint (Mentha × piperita L.) is a popular medicinal and aromatic plant, cultivated in several areas around the globe. Its functional and therapeutic potential has been largely attributed to its polyphenolic composition, yet rather a few investigations have delt with the preparation of polyphenol-enriched extracts from this plant. On this ground, this study was undertaken with the scope to establish a green, highly efficient extraction process, using food-grade deep eutectic solvents (DES). After an initial screening of several food-compatible DES reported in the literature, it was found that the most effective was glycerol-choline chloride (GL-ChCl), at a molar ratio of 2/1. This DES was subsequently used to carry out process optimization, using response surface methodology. The optimized conditions were determined to be DES/water proportion of 65 % (w/w), 143 min resident time and 80 °C. Under these conditions, the yield in total polyphenols was 72.78 ± 7.14 mg gallic acid equivalents g−1 of dry mass. Comparison with water and 60 % aqueous ethanol showed that extraction with GL-ChCl may provide extracts enriched in polyphenols, with increased antioxidant activity. The chromatographic analysis of the optimally produced extract revealed that the polyphenolic profile was dominated by eriocitrin, accompanied by luteolin glycosides and rosmarinic acid.