contains about 30 percent of its calories from fat, most meals are adequate for carotenoid absorption (Williams, Borleau and Erdman, 1998). Estimated lycopene intake in two studies varied from 593 mg/day using the U. S. Department of Agriculture-National Cancer Institute carotenoid food composition database to 1615 mg/day using the Block-NCI Health Habits and History Questionnaire (Clinton, 1998).
Table 1: Approximate lycopene content of various foods.
Table 2: Relative abundance of lycopene isomers in various commercial tomato products
Adapted from: Nguyen and Schwartz, 1998
III. Overview of lycopene chemistry.
i) Structure: Lycopene is an acyclic carotenoid which has 11 conjugated double bonds arranged linearly (Clinton, 1998). Lycopene lacks the beta-ionone ring structure so lacks the provitamin A activity of other carotenoids. The structure of carotenoids determines their color and photochemical properties, and lycopene produces the red color in fruits (Clinton, 1998).
ii) Function: The carotenoids act as antioxidants by quenching singlet oxygen. Of all the carotenoids tested, lycopene has been found to be the most efficient in quenching singlet oxygen. It has the ability to lose all the newly acquired energy through a series of rotational and vibrational interactions with the solvent and regenerate the intact lycopene (Krinsky, 1998).
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