Two molecules that share the same chemical formula can produce significantly different effects in an organism as a result of differences in their structure and arrangement, called isomerism.
The natural Astaxanthin molecule has two characteristic asymmetric carbon atoms that produce three different stereoisomers: (3S,3’S), (3R,3’S), and (3R,3’R). All have the same physical properties except for the direction in which they rotate polarized light, hence called optical isomers or enantiomers. Chemical behavior of the enantiomers can be very different when they react with biologically active molecules that are also optical isomers.
Optical isomers exist in many biologically active molecules of human body like enzymes, amino acids, proteins, DNA and sugars, so Astaxanthin enantiomers
can produce quite different biological and physiological effects when consumed by humans.
“Nature identical” claim of artificial astaxanthin synthesized from petrochemicals is not true, as it has different isomers that could act adversely upon health. Its main composition are 3R, 3’S and 3R, 3’R enantiomers, whose different physiological responses have not been studied. Remember the sad story about thalidomide optical isomers.
The 3S, 3’S optical isomer of astaxanthin has always been in the human food chain and it is safe. From microalgae phytoplankton through shrimp zooplankton and fishes, this wonderful molecule reaches food for human consumption. We do not expect surprise effects from the 3S, 3’S isomer.