In vitro absorption and lipid-lowering activity of baicalin esters synthesized by whole-cell catalyzed esterification

Baicalin, a phenolic glycoside with good lipid-lowering activity, has poor intestinal absorption due to low lipophilicity. In this study, six ester derivatives of baicalin, named BECn (n = 2, 3, 4, 6, 8, and 10) based on their fatty chain lengths, were synthesized by whole-cell catalyzed esterification to improve lipophilicity, and the intestinal absorption and lipid-lowering activity of the synthesized esters were investigated using cell models in vitro. BEC2, BEC3, and BEC4 exhibited higher P_app values than baicalin in Caco-2 cell monolayers. The lipid-lowering activity of the three esters was stronger than baicalin in the cell models of hepatic steatosis, adipocytes and foam macrophages, and was attributed to their higher intracellular accumulation and stronger direct activation of the carnitine palmitoyltransferase 1A. Moreover, these esters were easily hydrolyzed by carboxylesterase and were unstable at pH 7.4, which significantly weakened their absorption and lipid-lowering activity. This study laid the foundation for industrial production and practical application of BAI esters.