Natural deep eutectic solvents (NADESs) coupled with ultrasound-assisted extraction (UAE) were evaluated as an extraction technique for phenolic compounds from Crataegus monogyna leaves and flowers. Nine well-known hydrophilic NADESs were investigated as green extraction media, and their extractability was assessed in terms of major individual compounds, total flavan-3-ols and proanthocyanidins, as well as antioxidant activity. Water and ethanol–water solutions (70% and 50%, v/v) were used as reference solvents. An HPLC method was developed and partially validated for the quantitative determination of key individual components, including chlorogenic acid, hyperoside, vitexin, vitexin-2″-O-rhamnoside, and vitexin 2″-O-(4‴-O-acetyl)-rhamnoside. The subsequent chemometric analysis of the datasets revealed that the NADES systems choline chloride:urea:water (1:1:6) and choline chloride:glucose:water (5:2:25) exhibited pronounced extraction performance for all investigated metabolites, while preserving high antioxidant activity of the extracts. Pearson correlation coefficients and corresponding p-values demonstrated strong and statistically significant relationships among the majority of the investigated parameters: solvents’ physicochemical properties, the yield of phenolic compounds, and the antioxidant activity of the hawthorn extracts. The results highlight the potential of choline chloride based NADESs containing urea or glucose as alternative solvents for the green production of hawthorn-derived ingredients for functional foods, nutraceuticals, and herbal preparations, thereby contributing to the development of scalable, application-oriented extraction technologies.
Petkov et al. (Thu,) studied this question.