Carotenoids and carotenoid esters in potatoes (Solanum tuberosum L.):: New insights into an ancient vegetable

The carotenoid pattern of four yellow- and four, white-fleshed potato cultivars (Solanum tuberosum. L.), common on the German market, was investigated using HPLC and LC(APCI)=MS for identification and quantification of carotenoids. In each case, the carotenoid pattern was dominated by violaxanthin, antheraxanthin, lutein, and zeaxanthin, which were present in different ratios, whereas neoxanthin, beta-cryptoxanthin, and beta,beta-carotene generally are only minor constituents. In contrast to literature data, antheraxanthiin was found to be the only carotenoid epoxde present in native extracts: The total concentration of the four main carotenoids reached 175 mug/100 g, whereas the sum of carotenoid esters accounted for 41-131 mug/100 g. Therefore, carotenoid esters are regarded as quantitatively. significant compounds in potatoes. For LC(APCI)-MS analyses of carotenoid. esters, a two-stage, cleanup procedure was developed, involving column chromatography on silica gel and enzymatic cleavage of residual triacylglycerides by lipases. This facilitated. the direct identification of several. potato carotenoid esters without previous isolation of the compounds. Although the unequivocal identification of all parent carotenoids was not possible, the cleanup procedure proved to be highly efficient for LC(APCI)-MS analyses of very-low amounts of carotenoid esters.