The beta-carotene-rich alga Dunaliella bardawil as a source of retinol in a rat diet.

1. Dunaliella bardawil, a beta-carotene-accumulating alga, has been tested as a source of retinol and beta-carotene in a diet given to rats. The beta-carotene in this alga is composed of about equal amounts of the 9-cis and all-trans isomers. Male weanling rats were fed on a retinol-deficient diet for 60 d. Thereafter, the rats were divided into groups and fed on a diet deficient in retinol or supplemented with retinol, synthetic beta-carotene, dry alga or an algal oil-extract. Following further growth for 7 d, samples were taken for liver analyses of retinol, retinol isomers and beta-carotene. 2. Liver analyses revealed a comparable content of retinol and normal conversion rates in the rats grown on the diets supplemented with synthetic or natural beta-carotene. Rats fed on the alga and the algal-oil-supplemented diets accumulated 9-cis retinol in addition to the all-trans isomer. Rats fed on synthetic beta-carotene, alga and algal oil had a liver retinol: beta-carotene value of about 3:1. 3. These studies demonstrate the possibility of using dried D. bardawil or an oil extract of the alga as a dietary natural beta-carotene supplement which satisfies the total requirement of retinol in rats. 4. Rats fed on alga or on algal oil, accumulated in the liver 9-cis beta-carotene and all-trans beta-carotene in a ratio similar to that present in the alga.