Chromatographic performance on a C 30-bonded stationary phase of monohydroxycarotenoids with variable chain length or degree of desaturation and of lycopene isomers synthesized by various carotene desaturases

Abstract

Selectivity towards geometric isomers is a superior feature of a C 30 polymeric stationary phase. Therefore, lycopene isomers synthesized in Escherichia coli transformants by catalysis of divers carotene desaturases were separated on this stationary phase. Due to their spectral characteristics and by co-chromatography with nuclear magnetic resonance-characterized carotene standards, some of them could be identified. Most of the lycopene isomers were cyclized by lycopene cyclase yielding mainly 9 Z, 13 Z and all- E β-carotene. In contrast, 7,9,7′,9′ Z prolycopene is accumulating since it cannot be converted by this enzyme. Finally several acyclic hydroxycarotenoids with a chain of 30, 40 and 45 carbon atoms differing in the length of the polyene chain from 9 to 13 were separated on the C 30 stationary phase. Longer retention times were observed when the length of the molecule increased and also when the conjugated double bond system was extended. Corresponding monocyclic carotenoids were less retained on the C 30 stationary phase and derivatives with an ϵ-ionone end group eluted earlier than with a β-end group.