Carotenoids are the most widespread pigments in nature and they appear in all algae, higher plants, and many photosynthetic bacteria. Their role is to protect from light radiation in the red, orange, or yellow wavelengths. Chemically speaking, carotenoids are tetraterpenes, whereas carotenes are hydrocarbons and xanthophylls contain one or more ox­ygen molecules (Lobban and Harrison, 1994). All xanthophylls synthesized by higher plants, e. g. violaxanthin, antheraxanthin, zeaxanthin, neoxanthin, and lutein, can also be synthesized by green algae. However, these possess additional xanthophylls, that is, loroxanthin, astaxanthin, and canthaxanthin. Diatoxanthin, diadinoxanthin, and fucoxanthin can also be produced by brown algae or diatoms (Guedes et al., 2011c). In general, green algae contain p-carotene, lutein, violaxanthin, neoxanthin, and zeaxanthin, whereas red species contain mainly a — and p-carotene, lutein, and zeaxanthin. p-carotene, violaxanthin, and fucoxanthin are present chiefly in brown species (Haugan and Liaaen-Jensen, 1994).

Extraction of carotenoids from algae has been boosted in recent years in the alimentary and aquaculture fields (Lamers, Janssen et al., 2008), driven by consumers’ environmental and health awareness and commercial feasibility. The major large-scale applications are food and health. Carotenoids’ antioxidant properties have been shown to play a role in preventing pathologies linked to oxidative stress (Yan, Chuda et al., 1999).

Recall that most oxidation reactions in foods are deleterious, e. g., degradation of vitamins, pigments, and lipids, with consequent loss of nutritional value and development of off — flavors (Bannister, O’Neill et al., 1985; Fennema, 1996). On the other hand, carotenoids are particularly strong dyes, even at ppm levels. Specifically, canthaxanthin, astaxanthin, and lutein have been in regular use as pigments and accordingly have been included as ingredi­ents of feed for salmonid fish and trout as well as poultry, to enhance the reddish color of fish meat or the yellowish color of egg yolk (Lorenz and Cysewski, 2000; Plaza, Herrero et al.,

2009) . Furthermore, p-carotene has experienced an increasing demand as pro-vitamin A (ret­inol) in multivitamin preparations. It is usually included in the formulation of healthy foods under antioxidant claims (Krinsky and Johnson, 2005; Spolaore, Joannis-Cassan et al., 2006). Some carotenoids are part of vitamins, which have diverse biochemical functions, including hormones, antioxidants, mediators of cell signaling, and regulators of cell and tissue growth and differentiation (Holdt and Kraan, 2011).

In humans, oxidation reactions driven by reactive oxygen species can lead to protein damage as well as DNA decay or mutation; these may, in turn, lead to several syndromes, such as cardiovascular diseases, some kinds of cancer, and degenerative diseases, besides aging in general (Kohen and Nyska, 2002). As potential biological antioxidants, carotenoids have the ability to stimulate the immune system and may be involved in as many as 60 life — threatening diseases, including various forms of cancer, coronary heart diseases, premature aging, and arthritis (Mojaat, Pruvost et al., 2008). Carotenoids exhibit hypolipidemic and hypocholesterolemic effects as well (Guedes et al., 2011c). A summary of these bioactivities is provided in Table 10.5.

Concerning carotenoid extraction, methodologies such as solvent extraction, supercritical extraction, or expanded bed absorption chromatography can be applied, as described by Liam et al. (Liam, Anika et al., 2012).