Optimization of the ultrasound-assisted extraction of anthocyanins and total phenolic compounds in mulberry (Morus nigra) pulp

Abstract

New ultrasound-assisted extraction methods for the determination of anthocyanins and total phenolic compounds present in mulberries have been developed. Several extraction variables, including methanol composition (50–100%), temperature (10–70 C), ultrasound amplitude (30–70%), cycle (0.2–0.7 s), solvent pH (3–7) and solvent-solid ratio (10:1.5–20:1.5) were optimized. A Box–Behnken design in conjunction with a response surface methodology was employed to optimize the conditions for the maximum response based on 54 different experiments. Two response variables were considered: total anthocyanins and total phenolic compounds. Extraction temperature and solvent composition were found to be the most influential parameters for anthocyanins (48 C and 76%) and phenolic compounds (64 C and 61%). The developed methods showed high reproducibility and repeatability (RSD < 5%). Finally, the new methods were successfully applied to real samples in order to investigate the presence of anthocyanins and total phenolic compounds in several mulberry jams.