1H HR-MAS NMR of carotenoids in aqueous samples and raw vegetables

Carotenoids are linear C-40 tetraterpenoid hydrocarbons and represent a wide category of natural pigments. They are components of the pigment system of chloroplasts and are involved in the primary light absorption and the photon canalization of photosynthesis. Moreover, they also behave as quenchers of singlet oxygen, protecting cells and organisms against lipid peroxidation. Carotenoids have a strong lipophilic character and are usually analyzed in organic solvents. However, because of their biological activity, the characterization of these compounds in an aqueous environment or in the natural matrix is very important. One of the most important dietary carotenoids is beta-carotene, which has been extensively studied both in vivo and in model systems, but because of the low concentration and strong interaction with the biological matrix, beta-carotene has never been observed by NMR in solid aqueous samples. In the present work, a model system has been developed for the detection and identification of beta-carotene in solid aqueous samples by H-1 HR-MAS NMR. The efficiency of the model has led to the identification of beta-carotene in a raw vegetable matrix. Copyright (c) 2006 John Wiley & Sons, Ltd.