Preparative isolation of six major saponins from Platycodi Radix by high-speed counter-current chromatography.

INTRODUCTION

Platycosides, the primary constituents of Platycodi Radix, are known to have numerous and varied biological activities, exerting anti-inflammation, anti-allergy, anti-tumour, anti-obesity and anti-hyperlipidemia effects. However, effective methods for isolating and purifying platycosides from Platycodi Radix are not currently available.

OBJECTIVE

To develop an efficient method for the preparative separation of six platycosides from Platycodi Radix by high-speed counter-current chromatography (HSCCC) coupled with an evaporative light scattering detection (ELSD) system.

METHODOLOGY

Preparative separation was performed by water extraction using reversed-phase C(18) column chromatography on an HSCCC-ELSD system. A two-phase solvent system comprised hexane-n-butanol-water (1:40:20, v/v) and (1:10:5, v/v) was employed. Two other key parameters, revolution speed of the separation column and flow-rate of the mobile phase, were also investigated for optimum HSCCC performance. Each peak fraction obtained from separation of the platycosides was collected according to the ELSD elution profile and determined by HPLC.

RESULTS

Using the described method, six platycosides, all with purities of over 94%, could be isolated from 300 mg of the platycoside-enriched fraction. Their structures were characterized by electrospray ionisation mass spectrometry (ESI-MS), (1)H-NMR and (13)C-NMR.

CONCLUSION

Six of the main bioactive platycosides in Platycodi Radix could be isolated and purified systematically by HSCCC.