Preparative isolation and purification of anthocyanins from purple sweet potato by high‐speed counter‐current chromatography

High‐speed counter‐current chromatography (HSCCC) was applied to the preparative isolation and purification of peonidin 3‐ O ‐(6‐ O ‐( E )‐caffeoyl‐2‐ O ‐β‐ D ‐glucopyranosyl‐β‐ D ‐glucopyranoside)‐5‐ O ‐β‐ D ‐glucoside ( 1 ), cyanidin 3‐ O ‐(6‐ O ‐ p ‐coumaroyl)‐β‐ D ‐glucopyranoside ( 2 ), peonidin 3‐ O ‐(2‐ O ‐(6‐ O ‐( E )‐caffeoyl‐β‐ D ‐glucopyranosyl)‐6‐ O ‐( E )‐caffeoyl‐β‐ D ‐glucopyranoside)‐5‐ O ‐β‐ D ‐glucopyranoside ( 3 ), peonidin 3‐ O ‐(2‐ O ‐(6‐ O ‐( E )‐feruloyl‐β‐ D ‐glucopyranosyl)‐6‐ O ‐( E )‐caffeoyl‐β‐ D ‐glucopyranoside)‐5‐ O ‐β‐ D ‐glucopyranoside ( 4 ) from purple sweet potato. Separation of crude extracts (200 mg) from the roots of purple sweet potato using methyl tert ‐butyl ether/ n ‐butanol/acetonitrile/water/trifluoroacetic acid (1:4:1:5:0.01, v/v) as the two‐phase solvent system yielded 1 (15 mg), 2 (7 mg), 3 (10 mg), and 4 (12 mg). The purities of 1 – 4 were 95.5%, 95.0%, 97.8%, and 96.3%, respectively, as determined by HPLC. Compound 2 was isolated from purple sweet potato for the first time. The chemical structures of these components were identified by 1 H NMR, 13 C NMR and ESI‐MS n .