Sissel Hertzberg

The structure of myxoxanthophyll

Abstract The structure of myxoxanthophyll, the characteristic xanthophyll of blue-green algae, has been investigated by chemical and physical methods including NMR and mass spectra. The evidence presented suggests that chromatographically homogeneous myxoxanthophyll is a mixed (1′,2′-dihydro-3′,4′-didehydro-3,1′-dihydroxy-γ-caroten-2′-yl)-glycoside (IVc and IVd) 1 in which rhamnose is the dominant sugar moiety and a hexose a minor component.

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—II. : The carotenoids of Aphanizomenon flos-aquae

Abstract The carotenoid composition of Aphanizomenon flos-aquae has been re-examined in a quantitative manner. The epiphasic fraction comprised β-carotene (I), flavacin, aphanin and aphanicin. The last two were shown to be identical with echinenone (IV) and canthaxanthin (VI) respectively. The hypophasic fraction contained in addition to aphanizophyll small amounts of myxoxanthophyll. Aphanizophyll and myxoxanthophyll are different pigments.

New carotenoid glycosides from oscillatoria limosa

Abstract The carotenoid composition of Oscillatoria limosa has been studied in a quantitative manner. In addition to β-carotene, cryptoxanthin, echinenone, canthaxanthin and a zeaxanthin-like carotenoid, three new glycosidic carotenoids were encountered. These were assigned the gross structures myxol-2′- O -methylmethylpentoside (I), oscillol-2,2′-di-( O -methyl-methylpentoside) (IX) and 4-keto-myxol-2′-methylpentoside (XIII) on the basis of chemical and spectral evidence. The mass spectra of the acetylated glycosides were particularly informative.

The structure of oscillaxanthin

Abstract The chemical structure of oscillaxanthin has been investigated by modern methods including NMR and mass spectrometry and glycoside hydrolysis. The evidence obtained supports the tridecaene octa-ol structure 1,1′-dihydroxy-2,2′-di-β- l -rhamnosyl-1,2,1′,2′-tetrahydro-3,4,3′,4′-tetradehydrolycopene (I).

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).

The constitution of aphanizophyll

Abstract Chemical and physical evidence in favour of aphanizophyll being 4-hydroxymyxoxanthophyll (I) is discussed.

Alginate as Immobilization Material for Biocatalysts in Organic Solventsa

Entrapment in Ca-alginate gels can be accomplished under very mild conditions and is widely used for immobilization of whole Due to the high porosity of the alginate gel, free enzyme will normally leak out. However, in typical hydrophobic solvents, the enzyme will be retained inside the hydrogel bead. In these systems, the alginate gel beads will retain their volume. To establish the operational ability of alginate in continuous processes, some basic studies have been carried out and the results are summarized in this work. The volume stability (shrinkage) of calcium alginate gel beads made from both “high-G” (Laminaria hyperborea stipes, LF 10/60, provided by Protan A/S, Drammen, Norway) and “low-G” (Macrocystis pyriferu obtained from the Kelco Division of Merck, San Diego, California) alginates was studied for a range of organic solvents. The leakage of enzyme from “high-G” gel beads was also studied. The alginate beads were applied for lipase-catalyzed reactions in nonaqueous solvents. Lipase-catalyzed esterification and transesterification reactions in organic solvents are by now well established.6.’ These reactions have also been carried out in immobilized systems using different matrices such as hydrophobic and hydrophilic photo-cross-linkable resin prepolymers and urethane prepolymer~,’.~ as well as silica” and celite.’ The use of calcium alginate+ntrapped lipase for hydrolysis of triglycerides G-blocks.

ENZYMATIC HYDROLYSIS OF ESTERS OF ALKALI LABILE CAROTENOLS

Esters of alkali labile carotenols were hydrolyzed enzymatically with pig liver esterase in Tris-HCl buffer containing 10-85% methanol or acetone.The natural acetates peridinin, fucoxanthin, 19′-butanoyloxyfucoxanthin, pyrrhoxanthin and synthetic actinioerythrol diacetate provided the corresponding carotenols in 85%, 45%, (5 + 5 + 30)%, 65% and (30 + 3)% of the recovered carotenoid with total pigment recoveries 60%, 73%, 88%, 52% and 66%, respectively.(3RS, 3′RS)-Astaxanthin dipalmitate was converted enzymatically with lipase in low yield to the monopalmitate and free astaxanthin (5% + 6%, pigment recovery 93%) with a preferred hydrolysis of the S-ester. The (R,R:R,S:S,S) ratio of substrate dipalmitate and product astaxanthin changed from 1:2:1 to 1:5:3.

Carotenoids with two chromophores: carotenoid retinoates

In this study, carotenoid retinoates are described for the first time. The preparation was achieved by the azolide method. Various sec carotenols reacted with N-retinoylimidazol in the presence of catalytic amounts of sodium hydride. Mono- and diretinoates of (3R,3′R)-zeaxanthin and its (3S,3′S)-enantiomer, (9Z,9′Z; 3R,3′R)-alloxanthin, (3R,3′R)-7,8,7′,8′-tetrahydro-3,3′-dihydroxy-β,β-carotene-8,8′-dione and (3R,6R,3′R,6′R)-ε,ε-carotene-3,3′-diol (lactucaxanthin), as well as monoretinoates of (3R,3′RS,6′R)-3′-methoxy-β,ε-caroten-3-ol, (3R,3′RS,6′R)-3-methoxy-β,ε-caroten-3′-ol, (2R,6′RS)-β,ε-caroten-2-ol, (3R,3′S; meso)-astaxanthin and (2′R)-aleuriaxanthin are reported in this study. Spectroscopic properties (1H-NMR mass spectrometry, visible and circular dichroism spectra) are discussed. Studies on other carotenoid derivatives with two chromophores are referred to here.