Related Experiment Video
Updated: Sep 30, 2026

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
Isomerization of trans-astaxanthin to cis-isomers in organic solvents
Abstract:
The isomerization of trans-astaxanthin to cis-isomers in organic solvents was investigated. trans-Astaxanthin was dissolved in dimethyl sulfoxide, dichloromethane, chloroform, acetone, methanol, acetonitrile, and a mixture of dichloromethane and methanol (25:75) respectively, and heated at 35 degrees C followed by analyzing cis- and trans-astaxanthins in the solutions using HPLC. The isomerization rates of trans-astaxanthin were dependent on the solvent, and the following order was found: dichloromethane > chloroform > the mixture of dichloromethane and methanol (25:75) > methanol > acetonitrile > acetone > dimethyl sulfoxide. In different solvents, the relative contents of 9-cis- and 13-cis-astaxanthins formed during isomerization were different. In all solvents, 13-cis-isomer was the main cis-isomer from trans-astaxanthin. trans-Astaxanthin dissolved in dichloromethane or chloroform was very readily isomerized to cis-isomers, especially for dichloromethane, in which a maximum isomerization percentage was found and an equilibrium practically was reached after an appropriate time interval. Results also indicated that a higher temperature could promote markedly the isomerization of trans-astaxanthin.
Related Concept Videos
Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Disubstituted Cyclohexanes: cis-trans Isomerism
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
Isomerism
Stereoisomers
Stereoisomerism of Cyclic Compounds
SN2 Reaction: Stereochemistry
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.

