Synnøve Liaaen Jensen

The carotenoids of blue-green algae—I. : The carotenoids of Oscillatoria rubescens and an Athrospira sp.

Abstract The carotenoid composition of Oscillatoria rubescens has been re-examined in a quantitative manner. β-Carotene, zeaxanthin, echinenone (myxoxanthin), myxoxanthophyll and oscillaxanthin were found together with small amounts of cryptoxanthin and a hydroxylated ketocarotenoid whose probable structure is 4-keto-3′-hydroxy-β-carotene (I). The carotenoids of an Athrospira sp., whose systematic position is close to that of O. rubescens , were qualitatively and quantitatively very similar to those of O. rubescens , and the Athrospira sp. can be used as a more convenient source for myxoxanthophyll and oscillaxanthin—the structures of which are not yet established.

The carotenoids of blue-green algae—III. : A comparative study of mutatochrome and flavacin

Abstract Flavacin, obtained in small quantity from Aphanizomenon flos-aquae and Oscillatoria agardhii has been directly compared with mutatochrome (III), synthesized by monoperphthalic acid oxidation of β-carotene (I) to β-carotene-monoepoxide (II) and subsequent acid rearrangement. The results favour identity, although the available evidence does not rule out stereochemical differences. Complex metal hydride reduction of mutatochrome (III) (and flavacin) resulted in hydrogenolytic opening of the oxide ring. The main product 5-hydroxy-5,6-dihydro-β-carotene (IV) was dehydrated by phosphorous oxychloride to α-carotene (V).