All-trans β-carotene is absorbed preferentially to 9-cis β-carotene, but the latter accumulates in the tissues of domestic ferrets (mustela putorius puro)

Abstract

The algae Dunaliella bardawil and Dunaliella salina naturally contain large concentrations of all-trans and 9-cis β-carotene (βC). The purpose of this study was to compare the relative serum and tissue accumulation of all- trans and 9-cis βC in ferrets fed different ratios of all-trans/9-cis βC derived from two commercial sources, D. bardawil or D. salina (Betatene). Male ferrets (7 wk old) were fed carotene-free, pelleted diets for 27 d. Beginning on d 18, groups of ferrets (n = 6 or 7) received daily, one of six oral supplements varying in ratios of 9-cis and all-trans βC mixed with ~1.0mL of Ensure. Four supplements containing 5.2-8.3 μmol total βC were prepared from a 20% Betatene preparation, D. bardawil, a high-cis Betatene preparation, and Betatene further enriched in 9-cis βC with all-trans βC/9- cis βC ratios of 2.2, 1.5, 0.6 and 0.4, respectively. Two control supplements, high and low βC, were prepared from commercial βC beadlets. The high control supplement had an all-trans/9-cis ratio of 19.0, whereas 9- cis βC was not detected in the low supplement. On d 27, serum and tissues were obtained for HPLC analysis of βC and its isomers. Analysis of livers showed that all-trans βC was the primary isomer present, but 9-cis and other isomers were also detected in all groups. The hepatic all-trans/9-cis ratios were 5.9, 4.9, 2.5, 1.4, 52.2 and 47.5, respectively, for the groups listed above. Lower amounts of all-trans and 9-cis βC were found in kidneys compared with the liver, but ratios of all-trans/9-cis were not different among groups. Only trace amounts of 9-cis βC were found in serum. These results demonstrate that the algae D. bardawil and D. salina provide a bioavailable source of βC isomers, but, as in humans, absorption of 9-cis βC is poor and any 9-cis βC absorbed is apparently cleared by the liver.