|Smith Jr, James|
Submitted to: Journal of Cellular Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/1995
Publication Date: N/A
Interpretive Summary: The consumption of fruits and vegetables has been associated with reduced risk of several types of cancers. Carotenoids are abundant in these foods and have been proposed as cancer protective compounds because of their antioxidant and provitamin A activities. Lutein, an abundant carotenoid in many fruits and vegetables but without vitamin A activity, has been shown to possess strong antioxidant capability in laboratory studies. Results from the present study demonstrate that lutein and zeaxanthin, an isomer of lutein, are partially oxidized in vivo to several metabolites. These observations confirm the antioxidant activity of lutein in vivo which supports one of the proposed cancer protective mechanisms of carotenoids. Results and conclusions from these studies will benefit the diet and health community as well as policy makers.
Technical Abstract: Numerous epidemiological studies have demonstrated that consuming large quantities of fruits and vegetables reduces the risk for several types of human cancers. Carotenoids are abundant in fruits and vegetables and have been extensively studied as cancer preventive agents. A proposed mechanism of action for the protective effect of carotenoids against cancer is based on their antioxidant capability. Lutein and lycopene, abundant in most fruits and vegetables as well as human serum, have been shown to possess strong antioxidant capability. Among the metabolites of lutein, four result from oxidation and two from non-enzymatic dehydration. The metabolite of lycopene has been identified as 5,6-dihydroxy-5,6-dihydrolycopene, which apparently results from oxidation of lycopene to an intermediate, lycopene 5,6-epoxide the lycopene metabolite. Although, in vivo oxidation of lutein to its metabolites has been demonstrated based on data obtained from two human studies, in vivo oxidation of lycopene to its metabolite has not yet been established. Recent preliminary studies involving healthy subjects ingesting purified lutein and zeaxanthin are presented. The possible antioxidant mechanism of action for lutein and lycopene leading to the formation of the oxidation products of these promising chemopreventive agents are proposed.