Selective distribution of β-carotene stereoisomers in rat tissues

Dunaliella, a β-carotene-accumulating alga containing equal amounts of 9-cis and all-trans β-carotene stereoisomers, was compared with synthetic β-carotene composed of all-trans β-carotene with small residues of 15-cis β-carotene in rats. This study determined the bioavailability of the β-carotene stereoisomers in rats that were vitamin A depleted and fed with either Dunaliella β-carotene powder or synthetic all-trans β-carotene, both at 1 g/kg diet. Weight gain and tissue weights of rats in all groups were not different. High-performance liquid chromatography analysis for the distribution of vitamin A and carotenes in tissues and plasma showed that the original algal stereoisomers ratio of .92 was reduced in the liver and spleen to .78 and .56, respectively. The 15-cis-to-all-trans ratio in synthetic β-carotene of .05 was increased in the liver and spleen to .54 and .21, respectively. The selective distribution of β-carotene stereoisomers in rat tissues was directed to the spleen, an organ involved in immune response.