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. Under the conditions of LDI-MS the compounds form abundant radical molecular ions (M+*), whereas in the MALDI mass spectra abundant protonated molecular ions ([M + H]+) are observed. Characteristic fragment ions provide additional structural information. High-performance liquid chromatography (HPLC) coupled with UV/Vis photodiode detection was used to assist in retinoid characterization. Synthesis of 3-hydroxyretinal, 4-oxoretinal, and acycloretinal was performed by oxidative cleavage of the all-trans-carotenoids of zeaxanthin, canthaxanthin, and lycopene.
Institut für Physiologische Chemie I, Heinrich-Heine-Universität Düsseldorf, Germany.
T
T
Wingerath
D
D
Kirsch
B
B
Spengler
W
W
Stahl
D015394:Molecular Structure; D012172:Retinaldehyde / Q000031:analogs & derivatives* / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods; D013053:Spectrophotometry / Q000379:methods; D014212:Tretinoin / Q000031:analogs & derivatives* / Q000737:chemistry*; D014801:Vitamin A / Q000031:analogs & derivatives* / Q000737:chemistry*
D014801:Vitamin A; D014212:Tretinoin; D012172:Retinaldehyde