Chapter 6 Natural Deep Eutectic Solvents facilitating the extraction and storage of anthocyanins

Natural deep eutectic solvents (NADES) have a high solubilizing capacity, which is promising for their application in the extraction of active compounds from herbal medicines. Natural deep eutectic solvents are composed of neutral, acidic or basic compounds that form liquids of high viscosity when mixed in certain molar ratios. The viscosity may affect the extraction properties and stabilizing ability of NADES as well as the chromatographic properties of the extracts obtained. To address these problems, as a model, extraction methods with NADES were investigated in combination with HPLC-UV based metabolomics for the analysis of anthocyanins in flower petals of Catharanthus roseus. Stability tests of the anthocyanin extracts were also done. Multivariate data analysis indicates that NADES made of lactic acid-glucose (LGH), and 1,2-propanediol-choline chloride (PCH) present similar extractability of anthocyanins as acidified methanol. Furthermore, LGH exhibits higher stabilizing ability for cyanidin than acidified ethanol. Cyanidin was stable for 7 days at 4 oC and 3 month at -20 oC in LGH in the dark, which facilitates their extraction and analysis process. Compared with conventional organic solvents, NADES provide a greener and more stable approach for the extraction and storage of anthocyanins, implying that they have the potential to replace conventional organic solvents in health related areas such as food, pharmaceuticals, and cosmetics.