Application of lactic acid-based natural deep eutectic solvents for the extraction of phenolic compounds from winter savory

Satureja montana L. (Lamiaceae), known as winter savory, is an aromatic plant native to the Balkan Peninsula, valued for its use as a culinary spice. A diverse range of secondary metabolites, including phenolic compounds, contributes to the reported antioxidant, antidiabetic, anti-inflammatory, analgesic, and antimicrobial potential of this plant. Natural deep eutectic solvents (NADES) are systems designed according to the principles of green chemistry, with demonstrated high efficiency in the extraction of phenolics. The use of NADES, particularly those based on food-grade components, offers a sustainable and potentially food-compatible extraction approach for recovering bioactive compounds. Therefore, the aim of this study was to evaluate the applicability of lactic acid-based NADES in microwave-assisted extraction (MAE) of S. montana herb, with a focus on their efficiency in extracting selected phenolic compounds compared with water and ethanol.

Two NADES systems were prepared by heating and stirring, using food compatible components - lactic acid as the hydrogen bond donor and glucose or glycerol as hydrogen bond acceptors. In addition to NADES, water and 70% ethanol were used as extraction solvents. MAE was carried out in three 5-second cycles, at a microwave power of 180 W. The chemical profile of the extracts was assessed by High-Performance Liquid Chromatography (HPLC).

Rosmarinic acid, trans-cinnamic acid, rutin, quercetin, and naringenin were identified and quantified by HPLC. Extracts obtained using lactic acid:glucose system contained higher levels of rutin, quercetin, naringenin, and trans-cinnamic acid than those obtained with other solvents. Ethanol was more effective for rosmarinic acid extraction, while water was the least efficient solvent.

The obtained NADES-based extracts could be further explored as potential nutraceuticals, pending additional evaluation of their biological activity and safety.

Acknowledgments: This work was supported by the Provincial Secretariat for Higher Education and Scientific Research, Province of Vojvodina (Grant No. 003874431 2025 09418 003 000 000 001).