Isolation of Chlorogenic Acid and Isochlorogenic Acid from Purple Sweet Potato by High-speed Counter-current Chromatography

An efficient method for isolation and preparation of two phenolic compounds,namely cyaniding 3 chlorogenic acid(compound I) and isochlorogenic acid(compound II) from purple sweet potato was established by high-speed counter-current chromatography(HSCCC).Two compounds were separated with two-phase solvent systems,ethyl acetate-methanol-water(3:1:5,V/V) and n-hexane-ethyl acetate-methanol-water(1:3:1:4,V/V),respectively,at a flow rate of 1.5 mL/min and 2.0 mL/min,respectively.However,the same revolution speed of 850 r/min and the same injection volume of 200 mg were used.The results from HPLC analysis showed 28 mg of compound Ⅰ with 98.5% purity and 42 mg compound Ⅱ with 97% purity were obtained.The chemical structures of the two compounds were identified as 3-O-caffeoylquinic acid(Ⅰ) and 3,5-O-dicaffeoyquinic acid(Ⅱ) by mass spectrometry(MS) and nuclear magnetic resonance imaging(NMR).