Carotenoids in the Stick Insect, Ectatosoma tiaratum Isolation of ß,£-Caroten-2-ol and ß,£-Caroten-2-one

2-Oxo-carotenoids, 2-Hydroxy-carotenoids, [uC]/?-Carotene, Metabolism, Stick Insects The carotenoids of the stick insect, Ectatosoma tiaratum, were studied by spectroscopic and chemical methods. The /?,/?-type pigments are /?,/?-carotene, /?,/?-caroten-2-one, /?,/?-caroten-2-ol, /?,/?-carotene-2,2'-dione, 2'-hydroxy-/?,/?-caroten-2-one, ß,^-carotene-2,2'-diol, 3,4-didehydro-/?,/?carotene-2,2'-dione, 2'-hydroxy-3,4-didehydro-/?,/?-caroten-2-one, and 3,4,3',4'-tetradehydro-/?,/?carotene-2,2'-dione. In addition, the following ft,e-type pigments were identified: ß,e-carotene, /?,e-caroten-2-ol, and /?,e-caroten-2-one. This is the first report on the occurrence of ß,ecaroten-2-ol in an animal and of /?,e-caroten-2-one in nature at all. On treatment with BF3 in chloroform /?,e-caroten-2-ol is dehydrated to a specific product with the proposed structure of 2,3-didehydro-4,7'-re/ro-/?, e-carotene. The biogenesis of the /?,/?-type carotenoids from ß ,̂ -carotene is demonstrated by feeding [14C]/?-carotene to the insects. Radiolabel was incorporated into all major metabolites of this type. The metabolism of carotenoids in stick insects is discussed applying the “half-molecule sub­ strate” hypothesis to the enzymic transformations of the pigments.