Solvent-Dependent Flavonoid Profiles of Aronia melanocarpa Extracts Obtained Using Choline Chloride-Based Deep Eutectic Solvents and Their Antioxidant and Antimicrobial Activities

The present study compared the effectiveness of methanol and two choline chloride-based deep eutectic solvent systems containing lactic acid and citric acid for the extraction of phenolic compounds from Aronia melanocarpa. Extraction was performed under previously optimized conditions using a solid-to-liquid ratio of 1:20, an extraction temperature of 50 °C, and an extraction time of 60 minute. The phenolic composition of the extracts was determined by liquid chromatography coupled with high-resolution mass spectrometry. Antioxidant activity was evaluated by free radical scavenging and reducing power assays, while antimicrobial activity was assessed against nine bacterial strains and Candida albicans using the agar well diffusion method. The solvent system markedly influenced the phenolic and flavonoid composition of the extracts. The methanol extract contained the highest levels of chlorogenic acid (19,441.85 µg/g extract), quinic acid (433,957.67 µg/g extract), and isoquercitrin (16,010.96 µg/g extract). In contrast, the citric acid-based deep eutectic solvent extract was enriched in quercetin (2,649.73 µg/g extract), isorhamnetin (125.77 µg/g extract), narcissin (270.01 µg/g extract), liquiritigenin (1,383.35 µg/g extract), and phloridzin (437.59 µg/g extract). The lactic acid-based deep eutectic solvent extract exhibited the strongest free radical scavenging activity, with IC₅₀ values of 16.54 and 35.16 µg/mL, and also showed the highest cupric ion reducing antioxidant capacity. In contrast, the methanol extract demonstrated the greatest ferric ion reducing capacity. The citric acid-based deep eutectic solvent extract produced the largest inhibition zones against most of the tested microorganisms. These findings demonstrate that deep eutectic solvent composition determines not only the phenolic and flavonoid profile of Aronia melanocarpa extracts but also their dominant antioxidant mechanism and antimicrobial effectiveness, highlighting the potential of solvent-directed extraction for obtaining extracts with targeted biological properties.