Large-scale separation of baicalin and wogonoside from Scutellaria baicalensis Georgi by the combination of pH-zone-refining and conventional counter-current chromatography

The combined use of pH-zone-refining counter-current chromatography (CCC) and conventional CCC was successfully employed for the preparative separation and purification of baicalin and wogonoside from the traditional Chinese medicinal herb Scutellaria Baicalensis Georgi. A more environmentally friendly biphasic solvent system composed of n-butanol-ethyl acetate-water (2:3:5, v/v) was used for pH-zone-refining CCC, in which trifluoroacetic acid was added to a final concentration of 10 mmol L^-1 in the organic phase and ammonia was added to a final concentration of 10 mmol L^-1 in the aqueous phase while a two-phase solvent system composed of ethyl acetate-ethanol-3 mmol L^-1 hydrochloric acid (10:1:10, v/v) was used for the conventional CCC. Two elution modes including reverse displacement mode and normal displacement mode were investigated for pH-zone-refining CCC. The first run provided 186.7 mg of baicalin with a purity of 95.3% and 143.4 mg of a mixture of baicalin and wogonoside from 500 mg of the crude extracts of Scutellaria Baicalensis Georgi by pH-zone-refining CCC with reverse displacement elution mode. The mixture was further separated by means of a second run in conventional CCC, yielding 64.3 mg of baicalin with a purity of 98.2% and 46.1 mg of wogonoside with a purity of 98.9%.