(Z/E)-photoisomerization of C40-carotenoids by iodine

Abstract

The compositions of stereoisomeric mixtures of β-carotene (1), zeaxanthin (2), physaliene (3), natural violaxanthin (4), ‘semi-synthetic’ violaxanthin (5), capsorubin (6), capsanthin (7) and lutein-epoxide (8) have been investigated. The effect of end groups with different structures and stereochemistry on the cis-trans equilibrium, the rates of photo-induced cis–trans rearrangement of the zeaxanthin (2) set, and the ‘specific rate’(per unit light energy at a given wavelength) for several 13-cis carotenoids (2, 4, 6, 7, 9) have been determined.