Modulation of Selective Extraction of Phenolic Compounds from Capsicum chinense By-Products via UAE/NADES: Effects of Hydrogen Bond Acceptor, Extraction Time and Drying Method

Habanero pepper (Capsicum chinense Jacq. var. Jaguar) leaves are an underutilized by-product with potential as a source of polyphenols. This study evaluated UAE/NADES extraction as a tunable strategy to modulate selective polyphenol recovery rather than only maximizing total yield. A 2 × 3 × 2 factorial design was used to assess the hydrogen-bond acceptor (HBA) in fructose-based NADES, choline chloride (ChCl) or malic acid (MAc), ultrasound-assisted extraction (UAE) time (10, 20, and 30 min), and leaf drying method: freeze-drying (FzD) or oven-drying (OvD). Total phenolic content (TPC, Folin–Ciocalteu), antioxidant capacity (Ax, DPPH assay), and individual polyphenols by UPLC-DAD were determined. The highest TPC was obtained with ChCl from FzD leaves after 10 min of UAE (36.18 ± 0.70 mg GAE/g dry leaf). Maximum Ax was observed in OvD leaves after 30 min and was similar between HBAs (ChCl: 86.43 ± 0.65%; MAc: 86.95 ± 0.18%). UPLC-DAD confirmed compound-dependent selectivity, with catechin favored in MAc-FzD at 20 min (51.14 ± 1.07 mg/g dry leaf), chlorogenic acid in MAc-OvD at 10 min (16.05 ± 0.09 mg/g dry leaf), and quercetin + luteolin in MAc-FzD at 10 min (5.37 ± 0.05 mg/g dry leaf). This selective behavior may be associated with HBA-dependent solvent–solute affinity, polarity, hydrogen-bonding interactions, UAE-driven mass transfer, and drying-induced matrix changes. It is important to note that TPC, antioxidant capacity, and individual polyphenols showed a decoupled response, indicating that the overall spectrophotometric parameters did not necessarily reflect the polyphenol profile. Overall, the results show that UAE/NADES conditions can be directed toward target polyphenol profiles, supporting the valorization of C. chinense leaves as a source of tailored polyphenol extracts for future food, cosmetic, pharmaceutical, or nutraceutical applications.