Controlled acid hydrolysis and kinetics of flavone C-glycosides from trollflowers

Acid hydrolysis mechanisms of orientin-2″-O-galactopyranoside (OGA), orientin and other flavone C-glycosides in the trollflowers (Trollius chinensis Bunge) were studied in this report for the first time. Hydrolysis parameters including temperature, acidity, solvent and reaction time were comprehensively investigated. OGA could be hydrolyzed to orientin, followed by an isomerization to isoorientin via a reversible Wessely–Moser rearrangement reaction under stronger acidic conditions. A first-order kinetic model fitted the hydrolysis process of OGA well. Under the optimal hydrolysis conditions of 80 °C, 1.0 mol/L H+ and 7 h reaction time, about 77% OGA was transformed to orientin with no detectable isoorientin. These results could be helpful for better understanding of the acid hydrolysis kinetics of flavone C-glycosides, as well as the preparation of these valuable components under controlled acid hydrolysis conditions.

Graphical abstractUnder controlled acidic conditions, orientin-2″-O-galactopyranoside (1) could be hydrolyzed to orientin (2); orientin (2), and vitexin (3) could be hydrolyzed to corresponding isoorientin (4) or isovetexin (5) via a reversible Wessely–Moser rearrangement reaction. A first-order kinetic model fitted the hydrolysis process of 1.Figure optionsDownload full-size imageDownload as PowerPoint slide