Extraction and Purification of Acylated Anthocyanins

Anthocyanins (ACNs) are secondary metabolites widely distributed in nature and possess many different healthy properties that make these compounds useful as food supplements other than as ingredients for the dye industry. Therefore, the isolation of ACNs, including their acylated derivatives (AACNs), is a key step, and their extraction from the natural matrices is necessary to have concentrated and stable extracts. AACNs are generally more stable than the corresponding ACNs due to the presence of acyl residues on their skeleton. Over the years, different approaches have been set up to extract AACNs, and today the conventional solid to liquid method is overcome, even if still used, especially on a large scale; in this case, a purification step is required before the extract concentration process. As regards the extraction solvents, generally aqueous or hydroalcoholic mixtures are used, and acidification (using hydrochloric, malic, tartaric, ascorbic, citric, or acetic acid) adjusts the pH, increasing the extraction yield and stability. The need to have sustainable and green methods led to the development of different processes based on the use of water, ethanol, or natural deep eutectic solvents (NaDES). Ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and pressurized liquid extraction (PLE) are the currently most used approaches. As the development of such methods needs the set-up of different experimental parameters, the design of experiment (DoE) approach is a useful tool to reduce time, cost, and solvent consumption.