SEPARATION OF DITERPENOID ALKALOIDS BY HIGH PERFORMANCE CENTRIFUGAL PARTITION CHROMATOGRAPHY

Abstract

Complex diterpenoid alkaloids of close Rfvalues have been separated by High Performance Centrifugal Partition Chromatography (HPCPC). Model LLB-M (Series 1000) by Sanki Laboratories Inc. was used for these separations. Especially highly polar (on Al2O3) alkaloids which could not be isolated by conventional methods using a solid support, owing to irreversible retention, could be isolated easily as this separation method can be used in the reverse phase mode by careful selection of the biphasic solvent system. The HPCPC instrument was found easy to handle, dependable, applicable to the entire range of polarity of diterpenoid alkaloids, and gave reproducible results. When some of the fractions furnished a mixture of minor alkaloids, the mixture was resolved by a quick separation technique such as separation on a Chromatotron and preparative TLC. In all, eight different mixtures of known as well as crude alkaloidal mixtures were separated and the results are reported here. Isolated pure known compounds were identified through their spectroscopic (IR., 1H, 13C, DEPT NMR) and physical data, as well as comparison of their TLC behavior with that of authentic samples. A new diterpenoid alkaloid, 13-acetylvakhmatine (20), was also isolated in one of the separations.