Analysis of geometrical isomers of dietary carotenoids

Carotenoids are versatile isoprenoids of great importance in food science and nutrition. These compounds are natural colorants and key to combat vitamin A deficiency, a major global nutritional problem. In addition, carotenoids have health-promoting biological actions that can contribute to reduce the risk of serious diseases, including cancer, cardiovascular disease, skin, bone and eye conditions and metabolic disorders. Beneficial roles of carotenoids in cognition and fetal development are also attracting increased attention. The presence of double bonds cause carotenoids to be prone to geometrical isomerization. The distinction among geometrical isomers of carotenoids is important as there can be important differences in terms of bioavailability, stability during processing or even biological actions. This chapter summarizes strategies to separate and tentatively identify geometrical isomers of major dietary carotenoids (neoxanthin, violaxanthin, lutein, zeaxanthin, β-cryptoxanthin, α-carotene, β-carotene, lycopene, phytoene and phytofluene).