Deep eutectic solvents (DES) and natural deep eutectic solvents (NADES) are promising alternatives to traditional organic solvents for the extraction of polyphenols. They provide multiple advantages, such as improved extraction efficiency and increased solubility of the target compounds. These solvents are formed by mixing hydrogen bond donors and acceptors in specific molar ratios, which lowers their melting points. DES and NADES effectively dissolve a wide range of polyphenolic compounds that possess antioxidant and anti-inflammatory properties.
DES were prepared using urea and glycerol in a 1:2 (U1G2) ratio in a silicone bath for 60 min at temperatures of 70–90 °C with constant stirring. The infrared spectra of the starting materials – glycerol and urea – as well as those of the resulting DES were recorded. DES was then applied in the solid-liquid extraction of polyphenols from Helichrysum italicum, with 70% methanol as a reference standard. After extraction, total phenolic content (TPC), total flavonoids (TFC), and antioxidant activity assessed by DPPH, HRSA, CPRAC, and in vitro anti-inflammatory activity assessed by albumin denaturation inhibition (IAD) were measured. The DES (U¹G²) extract demonstrated superior performance compared to the 70% MeOH extract, with higher dry yield (322.65 vs. 303.80 mg), total phenolics (178.50 vs. 142.85 mg GAE/g DW), and flavonoids (154.82 vs. 109.43 mg QE/g DW). Antioxidant activity was stronger in CUPRAC (264.67 vs. 203.46 mM TE/g DW), DPPH assays (IC₅₀ = 4.24 vs. 8.89 µg/mL), and hydroxyl radical scavenging activity (HRSA, IC₅₀ = 100.33 vs. 107.27 µg/mL). Slightly better inhibition of albumin denaturation (155.61 vs. 150.64 µg/mL) also indicates enhanced anti-inflammatory potential. The results highlight the efficacy and sustainability of DES-based extractions, suggesting that this environmentally friendly approach can be scaled up for commercial extract production.
