Xanthophyll Esters in Fruits and Vegetables
Carotenoids possessing hydroxyl groups (xanthophylls) are often found as fatty acid esters in many fruits and vegetables. The developments in high resolution chromatographic and spectroscopic techniques have led to a detailed characterization of xanthophyll esters in commonly consumed fruits and vegetables, such as apples, apricots, mandarins, mangoes, papayas, red and chili peppers, potatoes or squash. Some more rich sources have been identified, like wolfberry (goji), sea buckthorn, persimmon, whose popularity is increasing due to the high content of bioactive compounds. Esterification increases the lipophilicity of xanthophylls and contributes to the sequestration of carotenoids, to the formation of specialized structures in the chromoplasts and to an increased photoprotection. The process occurs during ripening in fruits and it is associated with a significant change in colour. Even if the specific enzymes which catalyze the esterification process were not characterized yet in fruits, detailed analytical data regarding the carotenoid composition suggested a selectivity of these enzymes for certain fatty acids and selectivity for the ring in the case of non-symmetric xantophylls. Xanthophyll esters seem to be efficiently hydrolyzed and absorbed in humans leading to a comparable bioavailability to the unesterified compounds. In addition, the xanthophyll esters preserve the antioxidant capacity of the parent compounds while having a better stability in fruits during storage and processing. All these properties are important from the perspective of the use of fruits rich in xanthophyll esters as valuable components of the human diet and as sources of bioactive compounds in the prevention of severe degenerative diseases.
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