Abstract
High-speed counter-current chromatography was successfully applied to separate and purify bioactive ingredients from sweet potato leaves. Four caffeoylquinic acid derivatives and a mixture of two flavonoids were successfully obtained in one step. The caffeoylquinic acid derivatives were 3-O-caffeoylquinic acid (1), 4,5-di-O-caffeoylquinic acid (4), 3,5-di-O-caffeoylquinic acid (5), and 3,4-di-O-caffeoylquinic acid (6). The two-phase solvent system was composed of n-hexane\ethyl acetate\ethanol\water\acetic acid (1:5:2:4:0.1, v/v). The upper layer was used as the stationary phase, and the lower layer was used as the mobile phase. The flow rate was 1.5 mL/min, the revolution speed was 850 rpm, and the injection volume was 280 mg. The mixture of flavonoids was separated by preparative high-performance liquid chromatography into quercetin-3-O-β-D-galactopyranoside (2) and quercetin-3-O-β-D-glucoside (3). The purities of compounds 1–6 were 95.8% (5.4 mg), 99.5% (6.1 mg), 98.7% (15.1 mg), 97.8% (14.5 mg), 96.2% (10.3 mg), and 96.8% (7.8 mg), respectively, as determined by HPLC with a pulsed amperometric detector. The chemical structures were identified by electrospray ionization-tandem mass spectrometry and nuclear magnetic resonance imaging. The results showed the efficiency of the method in purifying bioactive compounds from sweet potato leaves, and compound 2 was separated from sweet potato for the first time.
ACKNOWLEDGMENT
This study was supported by the Education Department of Hunan Provincial (10C0799) and the Science and Technology Department of Hunan Provincial (2009NK3099).