Crypto xanthin

Organs n Carotenoids Zeaxanthin Crypto-Xanthin Lycopene a-Carotene (i-Carotene... 

The U.S./Canadian Dietary Reference Values report (Institute of Medicine, 2001) introduced the term retinol activity equivalent to take account of the incomplete absorption and metabolism of carotenoids 1 RAE = 1 /xg of all-fra s-retinol, 12 /xg of /3-carotene, and 24 /xg of a-carotene or /3-crypto-xanthin. On this basis, 1 iu of vitamin A activity = 3.6 /xg of /3-carotene or... 

In addition to the actual forms of vitamin A, related compounds, known as carotenes, are found in several fruits and vegetables. Carotene is also called (1) provitamin A, because it can be converted to vitamin A in the body and (2) precursor of vitamin A, because it precedes vitamin A. At least 10 of the carotenoids found in plants can be converted with varying efficiencies into vitamin A. Four of these carotenoids alpha-carotene, beta-carotene, gamma-carotene, and crypto-xanthine (the main carotenoid of corn)—are of particular importance due to their provitamin A activity. Of the four, beta-carotene (see Fig. V-25) has the highest vitamin A activity and provides about two-thirds of the vitamin A necessary for human nutrition. 

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