Carotenoid Profiling of a Red Seaweed Pyropia yezoensis: Insights into Biosynthetic Pathways in the Order Bangiales

Carotenoids are natural pigments that contribute to light harvesting and photo-protection in photosynthetic organisms. In this study, we analyzed the carotenoid profiles, including mono-hydroxy and epoxy-carotenoids, in the economically valuable red seaweed Pyropia yezoensis, to clarify the detailed biosynthetic and metabolic pathways in the order Bangiales. P. yezoensis contained lutein, zeaxanthin, -carotene, and -carotene, as major carotenoids in both the thallus and conchocelis stages. Monohydroxy intermediate carotenoids for the synthesis of lutein with an epsilon-ring from -carotene, -cryptoxanthin (,epsilon-caroten-3'-ol), and zeinoxanthin (,epsilon-caroten-3-ol) were identified. In addition, -cryptoxanthin, an intermediate in zeaxanthin synthesis from -carotene, was also detected. We also identified lutein-5,6-epoxide and antheraxanthin, which are metabolic products of epoxy conversion from lutein and zeaxanthin, respectively, by LC-MS and H-1-NMR. This is the first report of monohydroxy-carotenoids with an epsilon-ring and 5,6-epoxy-carotenoids in Bangiales. These results provide new insights into the biosynthetic and metabolic pathways of carotenoids in red seaweeds.