Carotenoid pigment found in fresh brown algae: Fucus virsoides (Don) J. Ag., Fucaceae. Also found in Zygnema pectinatum (Vauch.) Ag., Zygnemaceae and in Polysiphonia nigrescens (Dillw.) Grev., Rhodomelaceae. Isoln: Karrer et al., Helv. Chim. Acta 14, 628 (1931); Willsttter, Page, Ann. 404, 237 (1914). Structure: Bonnet et al., Chem. Commun. 1966, 515; J. Chem. Soc. C 1969, 429. Abs config: DeVille et al., Chem. Commun. 1969, 1311; K. Bernhard et al., Tetrahedron Lett. 1976, 115.