Large-scale purification of unstable, water-soluble secologanic acid using centrifugal partition chromatography

IntroductionSecologanic acid, a major secoiridoid in the flower buds of Lonicera japonica, is a fragile, highly polar compound that readily changes to epivogeloside or vogeloside after being dissolved in methanol. Thus, it is very difficult to obtain secologanic acid on a large-scale. ObjectiveTo develop a centrifugal partition chromatography (CPC) method for large-scale purification of secologanic acid with high purity from the flower buds of L. japonica. MethodsAfter fractionation with Diaion HP-20 macroporous resin, 30% methanol eluent was purified by CPC with a ternary biphasic solvent system with ethyl acetate/isopropanol/water (6:4:10, v/v/v). CPC was performed separately twice with the same solvent system, first in descending mode and second in ascending mode. ResultsAfter the first CPC operation, a secologanic acid enriched fraction (586mg) was obtained from 3g of crude extract, and secologanic acid (206mg) was isolated with a purity over 93% in the subsequent ascending mode with the same solvent system from a 586mg enriched fraction. In addition, it was confirmed that epivogeloside and vogeloside were reversely converted to secologanic acid in an aqueous acidic solution. ConclusionThese results demonstrate that CPC is a simple, effective, and rapid method for the purification of secologanic acid in the flower buds of L. japonica. Purification of secologanic acid, a major secoiridoid in the flower buds of Lonicera japonica, at a large-scale was performed by CPC with a ternary biphasic solvent system with ethyl acetate/isopropanol/water (6:4:10, v/v/v). CPC was performed separately two times with the same solvent system, first in descending mode and second in ascending mode. Secologanic acid converted to artifacts, epivogeloside or vogeloside in methanolic solution that was also reversed addition of acidic aqueous solution.