Abstract
In this study, we established a flow-rate gradient separation method to isolate four flavan-3-ol compounds with high purity from the seed coat extracts of Iris lactea by high-speed counter-current chromatography (HSCCC). First, the ethyl acetate extract was pre-separated by silica column chromatography fractionation to obtain the enriched flavan-ols sample (EFS). Then, the EFS was separated by HSCCC with a two-phase solvent system composed of n-hexane–ethyl acetate–methanol–water (0.75:12.5:1:12.5, v/v/v/v) by increasing the flow rate of the mobile phase from 1.5 to 3.0 mL/min after 120 min. The separation temperature was 30°C, the detection wavelength was 280 nm and the revolution speed was 900 rpm. By the optimized HSCCC method, 300 mg of the EFS was separated, yielding 58 mg of procyanidin B3, 72 mg of procyanidin B1, 52 mg of catechin, and 18 mg of procyanidin B7, at a purity of 98.23%, 99.05%, 99.03%, and 96.34% in 240 min. In this work, the flavan-3-ols in I. lactea are partly reviewed and the results can provide evidence to look for other rich source of procyanidins.