Isolation and structural elucidation of the predominant geometrical isomers of alpha-carotene.
The recent development and application of a polymeric C30 stationary phase have given unique separations of cis-trans carotenoid isomers in reversed-phase (RP) liquid chromatography (LC) owing to the exceptional shape selectivity of this stationary phase. In the present research, several geometrical isomers of alpha-carotene were at least partially resolved from a photo-isomerized mixture when chromatographed on a 3-microns polymeric C30 column. Double bond configurations of the five predominant alpha-carotene peaks, as isolated on a semi-preparative C30 column, were unambiguously assigned using 1H nuclear magnetic resonance (NMR) spectroscopy, giving the following order of elution: 13-cis, 13'-cis, all-trans, 9-cis, and 9'-cis geometrical forms. Electronic absorption spectra for these isomers were in agreement with the identification of peaks. The alpha-carotene isomers separated and identified herein had not been previously resolved in RPLC. Confirmation of the structures of geometrical alpha-carotene isomers will aid further studies on the possible physiological roles of these compounds in biological tissues.
Emenhiser
C
C
Department of Food Science, North Carolina State University, Raleigh 27695-7624, USA.
Englert
G
G
Sander
L C
LC
Ludwig
B
B
Schwartz
S J
SJ
D002338:Carotenoids / Q000737:chemistry* / Q000302:isolation & purification*; D002853:Chromatography, Liquid / Q000379:methods*; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy
D002338:Carotenoids; C041635:alpha-carotene