. Carotenoids, their comparative biochemistry. Carotenoids. CONVERSION OF CAROTENOIDS INTO VITAMIN A two a-ionone residues. ^ ^ Alteration of the side chain such as occurs in [3-dihydro-carotene ^ ^ destroys vitamin A activity. M? M? Me âV° I . i He Me Me Me Me / â â > /''^y\AWv\^AyV^^ /""^JUaW^^^ y-Me He P-carotenone â/-Me Me Me Me Me P-hydroxy-carotene. Me Mp M« p-d i hyd ro-carotene Recent work by Karrer and his associates on the production of caro- tenoid epoxides, has led to the necessity of modifying somewhat the statement than an unsubstituted ^-ionone residu
. Carotenoids, their comparative biochemistry. Carotenoids. CONVERSION OF CAROTENOIDS INTO VITAMIN A two a-ionone residues. ^ ^ Alteration of the side chain such as occurs in [3-dihydro-carotene ^ ^ destroys vitamin A activity. M? M? Me âV° I . i He Me Me Me Me / â â > /''^y\AWv\^AyV^^ /""^JUaW^^^ y-Me He P-carotenone â/-Me Me Me Me Me P-hydroxy-carotene. Me Mp M« p-d i hyd ro-carotene Recent work by Karrer and his associates on the production of caro- tenoid epoxides, has led to the necessity of modifying somewhat the statement than an unsubstituted ^-ionone residue is necessary for activity because 5 : 6-diepoxides, , (3-carotene-5 : 6-5' : 6'-diepoxide are vitamin A precursors ; ^ ^ the body can presumably convert the epoxide into [3-carotene. Me Me Me-y- Me Me Me 3-carotene-5 : 6-5' : 6' diepoxide However, when 5 : 6-epoxides are isomerized to 5 : 8-epoxides such compounds, , aurochrome, are inactive. ^^ The presence of a furanoid grouping does not interfere with activity of a molecule which contains in addition an unoxidized p-ionone or a 5 : 6-epoxy group, for example, mutatochrome ^ ^' ^ ° and luteochrome ^' are active : see next page. The work on the apo-carotenes revealed another interesting fact that, from the point of view of vitamin A activity, it matters little whether the terminal group is aldehydic, carboxy, or carbonyl. This ability of the body to deal with varying terminal groups has been further demonstrated recently with derivatives of vitamin A itself: 271. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Goodwin, T. W. (Trevor Walworth). New York, Chemical Pub. Co.
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