Preparative separation of caffeoylquinic acid isomers from Lonicerae japonicae Flos by pH-zone-refining counter-current chromatography and a strategy for selection of solvent systems with high sample loading capacities.

Caffeoylquinic acid derivatives exhibit anti-inflammatory, antioxidant, and antibacterial activities. We successfully applied pH-zone-refining counter-current chromatography (pH-ZRCCC) to separation of isomeric caffeoylquinic acids from Lonicerae japonicae Flos using a two-phase solvent system composed of ethyl acetate-n-butanol-acetonitrile-water (3:1:1:5, v/v/v/v). Trifluoroacetic acid (10 mM) was added to the upper phase as a retainer and ammonium hydroxide (10 mM) was added to the lower phase as an eluter. As a result, 167.8 mg of chlorogenic acid, 15.9 mg of isochlorogenic acid B, 103.4 mg of isochlorogenic acid C, and 156.0 mg of isochlorogenic acid A were obtained from 1.2 g of crude extract, and all compound purities were over 96%. In addition, by comparing the numeric values of partition coefficient of compounds, it was found that larger differences between the K values of adjacent compounds in the solvent systems resulted in higher sample loading capacities. pH-ZRCCC method is an efficient preparative separation of isomeric caffeoylquinic acids from natural products.