Comparative evaluation of growth inhibitory effect of stereoisomers of fucoxanthin in human cancer cell lines

Inhibitory effects of geometrical isomers of fucoxanthin - characteristic carotenoid of brown seaweeds - on the growth of various cancer cells and on human leukemia (HL-60), colon cancer (Caco-2) and prostate cancer cells (PC-3 and LNCap) were comparatively evaluated. All trans fucoxanthin was the major geometrical isomer (∼88%) found in the fresh brown seaweed (Undaria pinnatifida) apart from a small amount of 13-cis and 13'-cis isomers (∼9%). Incubation of the fucoxanthin isomeric mixtures, all trans fucoxanthin with a small amount of 13-cis and 13'-cis isomers, produced 9'-cis isomer (5%) and increased the contents of 13-cis, and 13'-cis isomers (27%). The antiproliferative effect of the mixture of 13-cis and 13'-cis isomers was stronger than all other geometrical isomers evaluated in the study. The inhibition of growth of HL-60 cells was higher in case of 13'-cis isomer followed by 13-cis and all-trans isomers. The potent inhibitory effect of 13-cis and 13'-cis fucoxanthin on HL-60 cells and Caco-2 cells could possibly be due to their higher apoptosis inducing activity