Cis-lycopene is more bioavailable than trans-lycopene in vitro and in vivo in lymph-cannulated ferrets.
Lycopene is the predominant carotenoid in tomatoes and tomato-based foods and is also a predominant carotenoid in human serum and tissues. Intake of lycopene-rich foods was recently associated with decreased risk for several chronic diseases. The observation that serum and tissue lycopene is more than 50% cis-lycopene, whereas tomatoes and tomato-based foods contain mainly all-trans-lycopene, has led to the hypothesis that cis-isomers of lycopene are more bioavailable. We tested this hypothesis both in vitro (study 1) and in vivo (study 2). In study 1, bile acid micelles containing crystalline lycopene were prepared. The crystalline lycopene used for these analyses was 54.4% cis-lycopene. The optically clear micelle preparation contained 75.9% cis-lycopene in repeated analyses. In study 2, mesenteric lymph duct cannulated ferrets were used to study the in vivo absorption of lycopene from LycoredTM (an ethyl acetate extract of tomatoes containing 5% lycopene by weight; of which 91% was all-trans lycopene). Before being anesthetized, male ferrets (n = 7) were dosed orally with 40 mg lycopene per kg body weight in soybean oil. Lymph secretions were collected, on ice, for 2 h. The residual stomach and small intestinal contents, mucosa lining, lymph secretion and serum were analyzed by HPLC. Whereas the dose, stomach and intestinal contents contained 6.2-17.5% cis-lycopene, the mesenteric lymph secretions contained significantly more, 77.4%, cis-lycopene (P < 0.01). These studies demonstrate that in ferrets, cis-isomers of lycopene are more bioavailable than trans-lycopene probably because cis-isomers are more soluble in bile acid micelles and may be preferentially incorporated into chylomicrons.