Carotenoid composition and its chemotaxonomic significance in leaves of ten species of the genus Ceratozamia (Cycads).

The qualitative composition and localization of carotenoids in leaflets of ten species of the genus Ceratozamia (Cycads) was investigated, and the distributions of 16 of these carotenoids, which were isolated and differently located in the chloroplast, are discussed. Eight classic carotenoids are located in the thylakoidal membranes of the chloroplasts of all ten of the species examined. In contrast, eight red keto-carotenoids are unusually located in several plastoglobules present in the stroma of nine species Ceratozamia mexicana Brongn. excluded. The characteristic red-brown transitory coloration shown by the newly formed leaflets during the first stages of development is due to this latter keto mixture. It is constituted of three very rare keto-carotenoids, which were, in our case, identified for the first time from the photosynthetic tissues (semi-beta-carotenone, triphasiaxanthin, and beta-carotenone). It is also constituted of four others, which are completely novel (ceratoxanthin, ceratozamiaxanthin, kuesteriaxanthin, and ceratoxanthone). Some hypotheses about their presence and function are presented.