Investigations of Carotenoid Reactions on Micro-Cel

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The reactivity of carotenoids with Micro-Cel C, a common chromatographic adsorbent, has been investigated further. α-Carotene was substantially converted to 4-hydroxy-α-carotene. Neither 4,4'-dihydroxy-α-carotene nor 3'-hydroxy-α-carotene was formed, suggesting that the reaction was limited to positions allylic to the conjugated double bond system. β-Apo-8-carotenal also underwent hydroxylation at the allylic 4-position of the β-ring, while retinal and β-ionone did not react. Lycopene reacted to such an extent that none of it remained unchanged. Other important characteristics of the reaction were determined by using β-carotene as the substrate. The hydroxylation process was stopped when Micro-Cel C was washed with acetone or methanol prior to mixing with β-carotene. Used Micro-Cel C could be recycled after removing the acetone from the first extraction of pigments. Drying the Micro-Cel C at 100 °C for 20 h decreased the amount of isocryptoxanthin produced but increased the level of dehydro-β-carotene 200-fold. The water content of the adsorbent was shown to play a key role in the reaction. The reaction was also shown to be solvent dependent. Petroleum ether was the best solvent while ethyl ether, chloroform, and acetone were inhibitors to different degrees. Methanol and ethanol changed the course of the reactions. © 1984, American Chemical Society. All rights reserved.

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Journal of Agricultural and Food Chemistry