Separation of Piper kadsura Using Preparative Supercritical Fluid Chromatography Combined with Preparative Reversed-Phase Liquid Chromatography

We have developed a separation strategy that employed preparative supercritical fluid chromatography (prep-SFC) combined with preparative reversed-phase liquid chromatography (prep-RPLC) to purify compounds from Piper kadsura. The complexity of the sample was effectively reduced by two steps of prep-SFC. The key experimental parameters of prep-SFC were systematically optimized, including an "average-pressure rule" scaling-up method for adjustment of the backpressure of the system. A mixed modifier consisting of ethanol/n-hexane was applied to provide a stable elution. Prep-RPLC was subsequently adopted to purify the SFC fractions due to its good orthogonality with SFC. Furthermore, chiral SFC was used to separate the structural analogues. As a result, 14 compounds with high purity were obtained from one fraction, including three pairs of diastereoisomers. These data indicate that the separation strategy using prep-SFC combined with prep-RPLC is an effective tool to separate complex samples such as natural products.