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.