Dunaliella bardawil, a beta-carotene-accumulating alga was treated by the bleaching
herbicide norflurazon to select sub-species rich with a mixture of 9-cis and all-trans
stereoisomers of phytoene and phytofluene. The present study determines the bioavailability
of phytoene and phytofluene with their stereoisomers in rats fed on a diet supplemented
with Dunaliella phytoene-rich spray dried powder. Three groups of female weanling
rats, eight animals each, were fed AIN diets for two weeks. The control consumed the
diet as is. The experimental group was supplemented with 50 g Dunaliella powder to
give phytoene/phytofluene at a level of 1 g/kg diet, and the placebo was provided
with the oxidized algae free of carotenoids at the same amount. Weight gain and tissues
weight of rats fed on the control diet, or on the experimental diets were statistically
same. Tissue analyses were carried out by liquid chromatography at the end of two
weeks feeding for vitamin A, carotenoids, phytoene and phytofluene and theirs stereoisomers.
Liver analyses revealed high hepatic storage of phytoene in the experimental group.
Analysis of the other tissues, adrenal, brain, heart, kidney, lung, and spleen detected
small amounts of phytoene in the adrenal, kidney and spleen and in the plasma. High-pressure
liquid chromatography for stereoisomeric composition was performed to all phytoene-containing
tissues. The original algal diet content of 9-cis-to-all-trans ratio of 1:1 was maintained
in the plasma and adrenal while in the liver, spleen and kidney the ratio was reduced
to 1:3. The preferential accumulation of all-trans phytoene over 9-cis phytoene in
the liver, spleen and kidney may be interpreted as indicating stronger antioxidative
effect of 9-cis phytoene over the all-trans isomer or alternatively, in vivo streoisomerization
of 9-cis phytoene to the all-trans structure.