Application of HPLC coupled with DAD, APcI-MS and NMR to the analysis of lutein and zeaxanthin stereoisomers in thermally processed vegetables

Publication Type

Journal contribution (peer reviewed)

Authors

Aman, R.; Biehl, J.; Carle, R.; Conrad, J.; Beifuss, U.; Schieber, A.

Year of publication

2005

Published in

Food Chem.

Band/Volume

92/4

DOI

10.1016/j.foodchem.2004.10.031

Page (from - to)

753-763

A method for the simultaneous detn. of lutein and zeaxanthin stereoisomers by HPLC-DAD was developed. For this purpose, (Z)-isomers of lutein and zeaxanthin were prepd. by iodine-catalyzed photoisomerization and their structures elucidated by 1D- and 2D-LC-NMR spectroscopy, by APcI-MS in the pos. mode, and by UV/Vis spectroscopy. Near baseline sepn. was achieved for (13-Z)-lutein, (13'-Z)-lutein, (all-E)-lutein, (9-Z)-lutein, (9'-Z)-lutein, (13-Z)-zeaxanthin, (all-E)-zeaxanthin, and (9-Z)-zeaxanthin. The influence of selected thermal treatments on degrdn. and isomerization of lutein and zeaxanthin was assessed. Sweet corn and spinach were sterilized (Tmax = 121 C, F = 5) and blanched (t = 2 min, steam), resp. Heating resulted in decreases in total lutein content in sweet corn by 26% and in spinach by 17%. Total zeaxanthin content in sweet corn decreased by 29%. The amt. of (Z)-isomers of lutein and zeaxanthin increased in sweet corn from 12% to 30% and 7% to 25%, resp., whereas in fresh spinach a decrease in lutein (Z)-stereoisomers from 21% to 14% was obsd