The keto-carotenoids of two marine coccoid members of the Eustigmatophyceae

Open Access
Publisher Website
Google Scholar
Abstract
In addition to previously reported major xanthophylls, Nannochloropsis (Nannochloris) oculata (Droop) Hibberd and Nannochloropsis (Monallantus) salina (Bourrelly) Hibberd were found to produce minor amounts of cryptoxanthin epoxides, zeaxanthin, antheraxanthin, neoxanthin, and eight to ten keto-carotenoids during photoautotrophic growth in culture. Five of the keto-carotenoids were identified as echinenone, canthaxanthin, astaxanthin and its monoester, and astacene. Culture ageing of both algal species from about 2 to 14 weeks caused a three- to fivefold increase in the proportions of both canthaxanthin and the astaxanthin family, and this increase was accompanied by a corresponding decrease in the combined zeaxanthin-antheraxanthin-violaxanthin group. However, the keto-carotenoids never achieved ageing-associated predominance in the total carotenoid mixture, where violaxanthin and vaucheriaxanthin ester persisted as the major xanthophylls. Astaxanthin and astacene have not been previously recorded from any member of the Eustigmatophyceae. The controversial question of eyespots occurring in N. oculata cells is discussed, and its probable connection with extraplastidic astaxanthin accumulation is considered.