Chromatographic analysis of cis/trans carotenoid isomers

Abstract

Cis/trans configurations of carotenoids are known to effect the biochemistry of carotenoids in certain situations. Methodology for separating carotenoid cis/trans isomers is of importance to nutritionists and food scientists because cis isomers of provitamin A carotenoids have lower provitamin A activities than the all- trans form. Traditional food processing and preservation methods, especially thermal treatments, induce the formation of cis isomeric forms. However, many challenges are apparent for identifying and analyzing cis/trans isomers present in foods and other biological tissues. The development of current chromatographic methods for the separation of carotenoid cis/trans isomers is reviewed. For the separation of β-carotene isomers, most procedures employ either Ca(OH) 2 or Vydac C 18 columns. In general, polymeric C 18 columns allow for the detection of cis carotenes, while monomeric C 18 columns provide for some separation of certain xanthophylls. The main cis isomers detected in foods are the 13- cis and 9- cis forms, although other forms have also been found (mainly 15- cis and various di- cis isomers). More studies involving the metabolism and physiological consequences of cis/trans isomers in the diet are needed. However, due to limitations in current techniques, further method development in the area of separation, detection and quantitation of cis/trans carotenoid isomers will be required.