Green extraction of anthocyanins from Solanum betaceum peel by natural deep eutectic solvents: optimization, recycling, and evaluation of antioxidant, anti-inflammatory and skin-whitening activities

Abstract

This study developed a green and sustainable extraction method for anthocyanins from Solanum betaceum peel using choline chloride–based natural deep eutectic solvents (NADES). Among seven tested systems, the choline chloride−1,4-butanediol (ChCl–BD) NADES exhibited the highest extraction yield (26.8 mg/g), significantly outperforming conventional 60% ethanol (12.3 mg/g). Optimization yielded ideal conditions of 60 °C, 1 h, a solid–liquid ratio of 1:20 g/mL, and 30% water content. The ChCl–BD DES showed good recyclability, retaining over 79% efficiency after four reuse cycles. Characterization by SEM, FTIR, and XRD confirmed effective disruption of the lignocellulosic matrix, facilitating anthocyanin release. Molecular docking revealed stronger interactions between anthocyanins and DES components than ethanol. The DES extract displayed superior thermal and storage stability, low cytotoxicity, and markedly better antioxidant, antibacterial, anti-inflammatory, and tyrosinase-inhibitory activities compared with the ethanol extract. Moreover, the DES extract exhibited enhanced skin permeation in a Franz diffusion cell assay, achieving 33.61% dermal absorption after 4 h. These results demonstrated that ChCl–BD NADES could serve as an efficient, recyclable, and multifunctional extraction platform, producing anthocyanin-rich extracts with promising applications in the fields of functional foods, cosmetics and pharmaceuticals.