|Smith Jr, James|
Submitted to: The Journal of Chromatography B: Biomedical Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/1995
Publication Date: N/A
Interpretive Summary: Carotenoids are a class of food micronutrients that have been extensively studied for their preventive effect against several cancers. Lutein, a dihydroxycarotenoid, is abundant in green vegetables and also is one of the prominent carotenoids observed in human plasma. Recently four oxidative metabolites of lutein were characterized and studied in human feeding experiments, the results of which revealed that in vivo oxidation of lutein was one of the key reactions in the metabolism of this carotenoid. The current studies further expand our knowledge of the in vivo metabolism of this important food carotenoid. Two dehydration products of lutein, anhydrolutein I and 2',3-anhydrolutein II, were isolated and extensively characterized in extracts of human plasma. Data from the isolated anhydroluteins were identical with data obtained from these compounds that had been chemically synthesized from lutein. The presence of anhydrolutein I and II in human plasma is believed to be due to the acid catalyzed dehydration of dietary lutein in the digestive system followed by the absorption of these compounds. These findings in conjunction with previous results indicate that lutein, one of the prominent carotenoids in the US food supply, is actively metabolized by the human body which may account for some of the preventive effect of this carotenoid and others against cancer.
Technical Abstract: All-E-(3R,6'R)-3-Hydroxy-3'4'-didehydro-beta,gamma-carotene (anhydrolutein I) and all-E-(3R,6'R)-3-hydroxy-2',3'-didehydro- beta,epsilon-carotene(2'3'-anhydrolutein II) have been isolated and characterized from extracts of human plasma by semipreparative High Performance Liquid Chromatography (HPLC) on a C(18)-reversed phase column. The identification of anhydroluteins was accomplished by comparison of the UV-visible absorption and mass spectral data as well as HPLC/UV-visible/mass spectrometry (MS) spiking experiments using fully characterized synthetic compounds. Partial synthesis of anhydroluteins from the reaction of lutein with 2% H(2)SO(4) in acetone, in addition to anhydrolutein I (54%) and 2',3'-anhydrolutein II (18.6%), also gave (3'R)-3'-Hydroxy-3,4'dehydro-beta-carotene (3'4'- anhydrolutein III, 19.3%). While anhydrolutein I has been shown to be usually accompanied by minute quantities of 2',3'- anhydrolutein II (ca. 7-10%) in human plasma, 3'4,'-anhydrolutein III has not been detected. The presence of anhydrolutein I and II in human plasma is believed to be due to acid catalyzed dehydration of the absorbed dietary lutein in the human digestive system.