Separation of Polyprenols Using a Monolithic Silica Column in High-Performance Liquid Chromatography

Abstract

The use of monolithic silica gel columns for the analysis of natural polyprenols have been described. Separation of natural polyprenols by high-performance liquid chromatography (HPLC) using the Chromolith Performance octadecylsilyl (ODS) monolithic silica column (Merck) was compared with that using a conventional microparticulate ODS-bonded silica column. A system comprising two connected monolithic columns afforded an equivalent separation at half the analysis time of the conventional method. Furthermore, ten connected columns achieved a tremendously high-resolution separation; complicated series of homologous polyprenols having geometric isomers were separated completely. Additionally, we attempted the analysis of naturally occurring polyprenols and dolichols using a monolithic silica capillary column for HPLC. First, separation of the polyprenol mixture alone was performed using a 250 × 0.2 mm i.d. ODS-monolith silica capillary column. The separation resolution (RS) between octadecaprenol (prenol 18) and nonadecaprenol (prenol 19) was two time or more higher than that recorded when a conventional ODS-silica particle-packed column (250 × 4.6 mm i.d.) was used under identical elution conditions. Next, a mixture of the prenol type (polyprenol) and dolichol type (dihydropolyprenol) was subjected to analysis using this capillary HPLC system, and each homologue was separated successfully. During analysis of the polyprenol fraction derived from Eucommia ulmoides leaves, in addition to the all-trans-polyprenol and cis-polyprenol that were previously identified, dolichols were observed as a single peak. This high-resolution and sensitive system is very useful for the analysis of compounds that are structurally similar to polyprenols and dolichols and have small amounts of these alcohols.