Effects of inorganic salts on the partition of iridoid glycosides in high-polarity solvent systems and their preparative separation from Lonicerae japonicae Flos by high-speed counter-current chromatography

Abstract

Iridoid glycosides are highly polar compounds in Lonicerae japonicae Flos which possesses many bioactivities such as anti-hepatitis, anti-inflammation, and anti-tumor, so establishment of an efficient method for purifying them is necessary. In this study, the effects of three factors including salt concentration, acid–base property, and ionic radius of inorganic salts on the partition of iridoid glycosides in the high-polarity two-phase solvent systems of high-speed counter-current chromatography (HSCCC) were discussed according to salting-out extraction theory. The results showed that all of the above three factors have significant adjustment effects on the partition of iridoid glycosides in the solvent systems. Subsequently, the high-polarity two-phase solvent systems composed of n-butanol:50% ammonium sulfate solution:water (3:2:2, v/v/v) and n-butanol:acetonitrile:10% sodium sulfate solution:water (3:1:2.4:2, v/v/v/v) were selected for iridoid glycosides separation using HSCCC. Five iridoid glycosides including secologanoside, vogeloside, sweroside, secoxyloganin, and demethylsecologanol were obtained from L. japonica Flos extracts, all compound purities were over 98%. All results demonstrated that the high-polarity solvent system with addition of inorganic salt is an effective method for separation of highly polar compounds from natural products by HSCCC.