Analysis of cyclic and acyclic analogs of retinol, retinoic acid, and retinal by laser desorption ionization-, matrix-assisted laser desorption ionization-mass spectrometry, and UV/Vis spectroscopy.

Laser desorption ionization (LDI)- and matrix-assisted laser desorption ionization (MALDI)-mass spectrometry (LDI-MS, MALDI-MS) at 337-nm laser wavelength were used to analyze retinol (vitamin A), retinoic acid, and retinal and their analogs 3-hydroxyretinol, 3-hydroxyretinoic acid, 3-hydroxyretinal, 4-oxoretinol, 4-oxoretinoic acid, 4-oxoretinal, 3,4-didehydroretinol (vitamin A(2)), 3,4-didehydroretinoic acid, 3,4-didehydroretinal, acycloretinol, acycloretinoic acid, and acycloretinal. The compounds exhibit sufficient ionizability which allows to obtain mass spectra by LDI which are similar in quality to those obtained by MALDI. Mass spectra were recorded with a linear time-of-flight (TOF) instrument or a reflectron-type (RETOF) instrument in positive-ion mode.

Xanthophyll esters in human skin.

Carotenol fatty acid esters in various fruits and vegetables are sources of carotenoids for humans and are cleaved during intestinal absorption to yield the parent xanthophyll. In the present study we demonstrate that low amounts of carotenol esters are present in human skin. Eighteen different carotenol fatty acid esters were separated in extracts from human skin by means of reversed-phase high-performance liquid chromatography.

High-performance liquid chromatography and laser desorption/ionization mass spectrometry of retinyl esters.

Laser desorption/ionization mass spectrometry (LDI-MS) at 337 nm laser wavelength was used to analyze retinol and several long-chain fatty acid esters of retinol. Employing this ionization technique helped to overcome the inherent problems resulting from thermal instability of retinyl esters which render this group of compounds rather difficult for standard ionization techniques. Mass spectra were recorded with a linear time-of-flight instrument in positive ion mode.

Analysis of carotenoids and carotenol fatty acid esters by matrix-assisted laser desorption ionization (MALDI) and MALDI-post-source-decay mass spectrometry.

Matrix-assisted laser desorption ionization (MALDI) time-of-flight mass spectrometry and MALDI post-source-decay (PSD) fragment ion mass analysis were employed to examine various model carotenoids and some of their fatty acid esters. It was demonstrated that the use of MALDI helps overcome problems resulting from the inherent thermal instability and lack of solubility which render this group of compounds rather difficult for conventional ionization techniques. Detection limits were in the subpicomolar range.