Carotenoid composition of marine red algae

Photosynthetic organisms possess carotenoids that function either as accessory, photoprotective, or structural pigments. Therefore, the carotenoid profile provides information about certain photoacclimation and photoprotection responses. Carotenoids are also important chemosystematic markers because specific enzymes mediate each step of carotenoid biosynthesis. For red algae, diverse and often contradictory carotenoid compositions have been reported. As a consequence, it is difficult to infer the physiological importance of carotenoids in Rhodophyta. To characterize the relationship between carotenoid composition, rhodophycean phylogeny, and the presence of potentially photoprotective pigments, we analyzed the carotenoid composition of 65 subtropical species from 12 orders and 18 rhodophyte families. Our results showed that red algae do not present a unique carotenoid profile. However, a common profile was observed up to the level of order, with exception of the Ceramiales and the Corallinales. The main difference between profiles is related to the xanthophyll that represents the major carotenoid. In some species lutein is the major carotenoid while in others it is substituted by zeaxanthin or antheraxanthin. The presence of this epoxy carotenoid together with the presence of violaxanthin that are xanthophyll cycle (XC)-related pigments was found in four of the 12 analyzed orders. The carotenoid pigment profiles are discussed in relation to Rhodophyta phylogeny, and it is suggested that the xanthophyll cycle-related pigments appeared early in the evolution of eukaryotic phototrophs.