SOME NATURAL AND SYNTHETIC ANTIOXIDANTS AS STABILIZERS OF BETA -CAROTENE CONVERSION INTO VITAMIN A

: The effect of antioxidants (vitamins C and E, quercetin, probucol, butylated hydroxytoluene) on the oxidation of beta-carotene and its conversion into retinal under the influence of beta-carotene 15,15'- dioxygenase (CDO) from rat intestinal mucosa was studied. The activity of CDO decreased in the presence of oxidants. Antioxidants protected both the substrate and the enzyme. The extent of the protection depended on the antioxidant type. The combined injection of antioxidants and beta-carotene to animals completely or partially prevented the inhibition of the intestinal CDO which was caused by products of non-enzymatic oxidation of beta-carotene. Vitamins C and E, which protected the enzyme--substrate complex in vivo and in vitro, were found to be the most efficient protectors of beta-carotene conversion into retinal.