Astaxanthin Astaxanthin is a fat-soluble carotenoid with a unique molecular struc ture that makes it an extremely effective antioxidant and a red natural color. The micro-alga Haematococcus pluvialis is the richest natural source for astaxanthin, capable of accumulating up to 5% of its dry biomass. It is the most abundant carotenoid pigment found in aquatic animals and the marine world. It is found in sea foods such as salmon, trout, red sea bream, shrimp, lobster and caviar. In fish, astaxanthin has been shown to have a synergistic effect on other important antioxi dants such as Vitamins C and E.