Isolation of isochlorogenic acid isomers in flower buds of Lonicera japonica by high-speed counter-current chromatography and preparative high performance liquid chromatography

•A new method of isolating isochlorogenic acid was established.•Specific units of isochlorogenic acids A and C were obtained at the same time with the good purities.•The total recoveries are 80.1% and 79.8% for isochlorogenic acids A and C, respectively.•The methods had several characteristics.•This method may be a suitable alternative for large scale separation of isochlorogenic acid isomers from ‘Jinyinhua’. An efficient method was established by HSCCC combined with prep-HPLC for separating isochlorogenic acid isomers from flower buds of Lonicera japonica. The partially purified sample from the methanol extract of flower buds of L. japonica by silica gel column was separated by HSCCC to result in a fraction containing two isochlorogenic acid isomers. The fraction was further isolated by prep-HPLC to yield isochlorogenic acid A and isochlorogenic acid C with purities of 98% and 96%, and the total recoveries at 80.1% and 79.8%, respectively. The chemical structures of isochlorogenic acid isomers were confirmed by electrospray ionization mass spectrometry (ESI-MS) and 1H nuclear magnetic resonance (NMR).