Preparative Isolation of Anthocyanins from Purple Sweet Potato by High-speed Counter-current Chromatography
High-speed counter-current chromatography(HSCCC) was successfully applied to separate and purify anthocyanins from purple sweet potato.With a two-phase solvent system composed of n-butanol-ethylacetate-0.5% acetic acid(3∶1∶4,V/V),the upper phase as stationary phase,the lower phase as mobile phase at a flow rate of 2.0 mL/min,and injection volume of 300 mg,a mixgure of two anthocyanins was received by undertaking HSCCC.Subsequently,a refining HSCCC was performed to separate and purify these two compounds,with a two-phase solvent system of 0.2% trifluoroacetic acid-n-butanol-methyl tertiary butyl ether-acetonitrile(6∶5∶2∶1,V/V),the upper phase as stationary phase,the lower phase as mobile phase at a flow rate of 1.5 mL/min,and injection volume of 100 mg.the two compounds were obtained separately with purities of 98.5% and 96.7%,respectively.The chemical structures of the two isolated compounds were identified by UV-VIS、ESI-MS/MS and NMR.Compound 1 was identified as peonidin 3-O-{6-O-(E)-caffeyl-2-O-[6-O-(E)-p-hydroxybenzoy-β-D-glucopyranoside]-β-D-glucopyranoside}-[5-O-(β-D-glucopyranoside)] and Compound 2 was identified as peonidin3-O-{6-O-(E)-caffeyl-2-O-[6-O-(E)-ferulyl-β-D-glucopyranoside]-β-D-glucopyranoside}-[5-O-(β-D-glucopyranoside)].63 mg of Compound 1 and 48 mg of Compound 2 were obtained from 450 g of purple sweet potato.In conclusion,counter-current chromatography was shown to be an efficient,stable and reliable technique for the isolation of anthocyanins from purple sweet potato.