Effect of Esterification of Natural Dyes with Glycosides on Dyeing Properties of Natural Fibers in Supercritical Carbon Dioxide

The color-rendering abilities of esterified natural dyes are influenced by the structure of their parent dyes and the position at which the ester group is introduced, resulting in low efficiency in screening and synthesizing suitable esterified natural dyes for dyeing natural fibers with supercritical carbon dioxide. In this study, density functional theory was used to quickly screen the parent natural dyes and esterification position of natural dyes. The findings indicated that B3LYP/def2-TZVP level and CAM-B3LYP (ω = 0.01)/def2-TZVP level yield the most accurate UV–vis absorption spectra calculations for natural dyes and their esterified derivatives, as evidenced by the smallest error compared to experimental values. The rutin, the carminic acid, and the icariin as the parent dyes were more suitable for esterification, and the introduction of ester groups solely on the glycosides of these dyes had negligible impact on their color-rendering abilities. Furthermore, considering the influence of ester groups on natural dye solubility, it was observed that the dyeing properties of glycoside esterified products derived from rutin, carminic acid, and icariin were better than those of their parent dyes, rendering them more appropriate for dyeing natural fibers in supercritical carbon dioxide.