Synthesis and Properties of Site-Specific Acetylated Anthocyanins: Focusing on Cyanidin-3-O-glucoside and Malvidin-3-O-glucoside

Anthocyanins are widely used water-soluble pigments with various activities, which are attributed to their flavylium salt and polyhydroxy structure. However, this also leads to low lipid solubility and stability. Acylation modification has always been an attempt by researchers to improve it. In this study, two site-specific acylated anthocyanins, cyanidin-3-O-(2″-acetyl)-glucoside (C3AG) and malvidin-3-O-(2″-acetyl)-glucoside (M3AG), were prepared by optimizing the removal conditions of the protecting group through the general anthocyanin total synthesis route established in the early stage. The accurate positioning of the acylation is determined by MS/MS and 2D NMR. By comparing the oil-water partition coefficient, antioxidant activity, color, and thermal stability of the two acylated anthocyanins, it was found that the 2″ acylated anthocyanin achieved better lipid solubility and stability, but the antioxidant activity showed variability. These results together prove that these acylated anthocyanins have been optimized in application scenarios with little impact on the original activity. Therefore, this work not only provides a reference method for the acylation modification of anthocyanins but also promotes their application in the food and cosmetics industries.