Enzymatic Acylation of Isoorientin and Isovitexin from Bamboo-Leaf Extracts with Fatty Acids and Antiradical Activity of the Acylated Derivatives

Abstract

This study enzymatically acrylates two flavonoids from bamboo-leaf extracts, isoorientin and isovitexin, with different fatty acids as acyl donors using Candida antarctica lipase B (CALB). The conversion yield ranged from 35 to 80% for fatty acids with different chain lengths. Higher isoorientin and isovitexin conversion yields (>75%) were obtained using lauric acid in tert-amyl-alcohol as the reaction medium. (1)H and (13)C nuclear magnetic resonance spectroscopy analysis showed that, in the presence of CALB, acylation occurred at the isoorientin and isovitexin primary hydroxyl group of glucose moiety and only monoesters were detected. Introducing an acyl group into isoorientin and isovitexin significantly improved their lipophilicity but reduced their antiradical activity.