Effectiveness of Natural Deep Eutectic Solvents (NADES) in Extracting Bioactive Compounds from <i>Salvia sclarea</i> : HPLC-DAD Analysis, Antioxidant and Enzymes Inhibition Potential Evaluation

The current study aimed to investigate the efficacy of green solvents to extract bioactive compounds from S. sclarea and evaluate their antioxidant and enzyme inhibition potential. Three natural deep eutectic solvent (NADES) formulations were synthesized: NADES-1 (choline chloride: citric acid 1:2), NADES-2 (choline chloride: glucose 1:2), and NADES-3 (choline chloride: glycerol 1:2). The HPLC-DAD analysis of NADES extracts showed that rosmarinic acid was found in high concentrations in NADES-2 (44.56 ± 0.28 μg/g), NADES-3 (29.49 ± 0.31 μg/g), and NADES-1 (25.63 ± 0.35 μg/g), respectively, while trans-cinnamic acid was detected exclusively in NADES-1. Similarly, chlorogenic acid and p-hydroxy benzoic acid were detected only in NADES-2, whereas ellagic acid was unique to NADES-3. In vitro antioxidant activity, assessed via different assays including (1) the β-carotene-linoleic acid test, (2) the DPPH test, (3) the ABTS test, (4) the CUPRAC test, and (5) the metal chelating test, demonstrated significant antioxidant activity across all NADES extracts, with NADES-2 exhibiting superior efficacy, exceeding the performance of reference standards (BHA and α-tocopherol). Furthermore, NADES-2 exhibited considerable inhibitory effects against AChE (IC50 = 107.7 ± 0.95 μg/mL) and BChE (IC50 = 96.81 ± 0.87 μg/mL). Conversely, each of the NADES extracts showed minimal inhibition of urease (<21%), indicating limited relevance for urease-related pathologies. These findings underscore the capacity of NADES as sustainable, high-efficiency solvents for the targeted extraction of bioactive phytochemicals, with NADES-2 emerging as a particularly promising candidate for antioxidant and cholinesterase-inhibitory applications. Further studies are recommended to elucidate the mechanistic underpinnings of NADES selectivity and to expand their utility in large-scale extraction and isolation of bioactive compounds from natural sources.