Matrix-Driven Modulation of Phenolic Profiles from Euterpe oleracea and Oenocarpus bacaba Using Natural Deep Eutectic Solvents

Abstract

This study investigated the influence of solvent composition on the extraction efficiency and selectivity of phenolic compounds from the Amazonian fruits açaí (Euterpe oleracea) and bacaba (Oenocarpus bacaba). Six choline chloride-based natural deep eutectic solvents (NaDES), combined with different hydrogen bond donors (glycerol, 1,2-propanediol, citric acid, lactic acid, oxalic acid, and urea), were compared with acidified methanol. Extracts were evaluated for total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity using FRAP, DPPH, and ORAC assays. In açaí, methanol exhibited the highest TPC and reducing capacity, whereas acid-based NaDESs enhanced phenolic recovery in a matrix-dependent manner. In bacaba, choline chloride–citric acid enhanced total phenolic recovery compared to methanol, highlighting matrix-dependent solvent performance. Differences among FRAP, DPPH, and ORAC responses reflected variations in phenolic composition rather than total concentration alone. HPLC-DAD analysis revealed solvent-selective enrichment of anthocyanins, chlorogenic acid, flavan-3-ols, and rutin, particularly with acid-based NaDES formulations. Molecular docking provided complementary mechanistic insight by indicating favorable interactions between major phenolics and polyphenol oxidase. Overall, the results indicate that choline chloride-based NaDESs can function as tunable extraction systems capable of modulating phenolic profiles in a matrix-dependent manner, representing promising alternatives to conventional organic solvents for phenolic recovery from Amazonian fruits.