Preparation and purification of raffinose family oligosaccharides from Rehmannia glutinosa Libosch. by fast protein liquid chromatography coupled with refractive index detection

Abstract

Raffinose family oligosaccharides (RFOs) were extracted and isolated from Rehmannia glutinosa Libosch. by using microwave-assisted extraction and fast protein liquid chromatography coupled with refractive index detection (FPLC-RID). After extraction with 60% ethanol (v/v) and decolorization with MCI gel CHP20P, total oligosaccharides were purified by using FPLC-RID coupled with the Bio-Gel P2 column eluted with water at the flow rate of 0.3mL/min. Three pure oligosaccharides (DP3–DP5) were obtained with the yields of 1.72%, 7.52% and 0.51%, respectively, as well as identified as raffinose, stachyose and verbascose from the results of liquid chromatography coupled with tandem mass spectroscopy (LC–MS/MS) and gas chromatography coupled with mass spectroscopy (GC–MS) analysis. A large-scale of pure RFOs was automatically and efficiently separated from R. glutinosa by using FPLC-RID method, which was beneficial for the qualitative and quantitative analysis of RFOs in R. glutinosa and their products.