Geometrical isomers of violaxanthin in orange juice

The geometrical isomers of carotenoids are now attracting considerable interest, due in part to the fact that they are known to behave differently in terms of susceptibility to oxidation, vitamin A activity and bioavailability. The study of such isomers has been facilitated by the development of the C30 stationary phase, which has made it possible to evaluate their occurrence in any source in a rapid fashion. In this study, the violaxanthin ((3S,5R,6S,3′S,5′R,6′S)-5,6:5′,6′-diepoxy-5,6,5′,6′-tetrahydro-β,β-carotene-3,3′-diol) fraction of orange juice (Citrus sinensis L. Osbeck) was isolated by thin-layer chromatography (TLC) to identify the different geometrical isomers occurring in it. Under the HPLC conditions described, several violaxanthin isomers were detected, of which (all-E)-violaxanthin and, above all, (9Z)-violaxanthin, happened to be the most important in quantitative terms.