Enhanced Extraction and Separation with HPLC-DAD of Phenolic and Flavonoid Antioxidants from L. Leaves Using Tailored Terpenoid-Based NADES: Comparative Assessment of Antiradical and Antimicrobial Activities.

This study evaluates Natural Deep Eutectic Solvents (NADES) for extracting antioxidant compounds from dried leaves, compared to traditional ethanol extraction. NADES were synthesized using terpenoids (menthol and β-citronellol) and organic acids (lactic and capric acid), characterized by favorable viscosity, density, and pH, ensuring liquid stability at ambient temperature. NADES extraction outperformed ethanol, with NADES 1 yielding the highest bioactive contents: 83.66 Eq GA/mg, 786.55 Eq Q/mg, and 0.78 Eq C/mg versus ethanol's 58.49 Eq GA/mg, 363.23 Eq Q/mg, and 0.44 Eq C/mg. HPLC-DAD analysis identified higher levels of phenolic acids (caffeic and syringic acid) and flavonoids (rutin and quercetin) in NADES extracts, compounds absent in ethanol. Antioxidant potential, assessed via IC values, confirmed superior activity for NADES extracts (NADES 1-Ext: IC 28.10 ± 1.73 µg/µL) compared to ethanol (IC 1615.97 ± 5.34 µg/µL), and the Trolox method has confirmed extensively this superiority. Additionally, NADES demonstrated improved antimicrobial effects, varying with microorganisms. Despite their high viscosity potentially limiting extraction efficiency, adjusting temperature offers a promising approach to enhance mass transfer. These findings emphasize NADES as a sustainable alternative for bioactive compound extraction, paving the way for optimizing extraction techniques through viscosity reduction strategies.