Einar Skarstad Egeland

Additional carotenoid prototype representatives and a general chemosystematic evaluation of carotenoids in prasinophyceae (chlorophyta)

Abstract Quantitative carotenoid analyses of 3 additional species representing each of three pigment types of Prasinophyte algae grown in pure culture are reported. The carotenoids were characterized by chromatographic (TLC, HPLC), spectroscopic (visible and mass spectroscopy, and, in part, 1H NMR, circular dichroism), and chemical methods. Preprasinoxanthin was isolated for the first time and the structure of 6′-hydroxysiphonaxanthin 19-(trans-Δ2-dodecenoate) was elucidated. The presence of siphonein, identified as siphonaxanthin 19-(trans-Δ2-dodecenoate) in Prasinophyceae was confirmed. Small amounts of the corresponding trans-Δ2-decenoates were present. Authentic siphonaxanthin 19-(trans-Δ2-dodecenoate) was isolated from Codium fragile for comparison. Pyramimonas amylifera belonged to the siphonein type. Prasinococcus capsulatus produced carotenoids of the prasinoxanthin/uriolide type, whereas Nephroselmis olivacea only contained common green algal carotenoids. A chemosystematic evaluation is made on the basis of 13 species examined by methods including mass spectroscopy and supplemented by less documented literature data on 26 species. Plausible biosynthetic routes are proposed from structural interrelationships, including chiralities. The Prasinophyceae displays a diversified carotenoid complement; 30 carotenoids have been identified, 14 of which are peculiar to this algal class. Three carotenoid prototypes emerge: type 1, producing only common green algal type carotenoids; type 2 with additional carotenoids of the siphonaxanthin series; and type 3 with additional carotenoids of the prasinoxanthin/uriolide series. Carotenoids with e- and γ-end groups are abundant. The 7,8-dihydro feature of the unique uriolide series is compatible with unprecedented cyclization of the least unsaturated end group of neurosporene by an e-cyclase.

Carotenoids from further prasinophytes

Abstract The qualitative and quantitative carotenoid composition of seven prasinophytes (eight clones) have been examined by chromatographic (TLC and HPLC) and spectroscopic methods (VIS, CD and mass spectra). The prasinophytes studied fall into two pigment types: (A) those producing common green algal carotenoids (β,β-carotene, β,ϵ-carotene, lutein, zeaxanthin and the epoxides violaxanthin and neoxanthin) and (B) prasinophytes synthesising carotenoids peculiar to this algal class (prasinoxanthin, anhydroprasinoxanthin, uriolide, anhydrouriolide, micromonal, anhydromicromonal, micromonol, anhydromicromonol and dihydrolutein), where prasinoxanthin is a major carotenoid. Mantoniella squamata (clone 2) was grown under both low and high light intensity, revealing differences in carotenoid composition. Lutein together with lesser amounts of zeaxanthin and its epoxides were only detected at high light intensity. Three previously unidentified carotenoids were identified as prasinoxanthin (xanthophyll K), micromonal and dihydrolutein.

PIGMENTS OF BATHYCOCCUS PRASINOS (PRASINOPHYCEAE): METHODOLOGICAL AND CHEMOSYSTEMATIC IMPLICATIONS1,2

Bathycoccus prasinos Eikrem et Throndsen exhibited a complex carotenoid distribution pattern including the carotenes β,β‐carotene (0.8% of total carotenoids) and β, ° Carotene (0.4%) and several xanthophylls. These were prasinoxanthin (49% of total carotenoids), micromonal (16%), neoxanthin (14%), uriolide (7%), violaxanthin (0.8%), 31‐dehydrouriolide (0.8%), dihydrolutein (0.1%), two partly characterized esterified carotenols (together 10%), and five minor unidentified carotenols (together 2%). The identifications were based on high‐performance liquid chromatography (HPLC), thin‐layer chromatography (TLC), visible spectroscopy (VIS), and mass spectra (MS) and in part on 1H nuclear magnetic resonance (NMR), circular dichroism (CD), and chemical derivatization. The carotenoid composition of B. prasinos was related to that of other prasinoxanthin / uriolide / micromonal‐producing prasinophytes (Mantoniella squamata, Micromonas pusilla, and Pseudoscourfieldia marina). The relative distribution of chlorophylls (w/w) were chlorophyll a (chl a; 63%), chl b (31%), and an unknown chl c‐like chlorophyll (7%) with spectral characteristics similar to magnesium 2,4‐divinylphaeoporphyrin a, monomethyl ester, compatible with other prasinophytes. The chemosystematic data and ultrastructural characteristics for the order Mamiellales are discussed. We conclude that HPLC studies alone are insufficient for the identification and characterization of the carotenoids, including the minor carotenoids essential for biosynthetic/chemosystematic considerations.

Algal carotenoids. Part 64. Structure and chemistry of 4-keto-19′-hexanoyloxyfucoxanthin with a novel carotenoid end group

The structural elucidation of a new carotenoid 4-keto-19′-hexanoyloxyfucoxanthin 5 from Emiliania huxleyi is documented by chromatographic (HPLC, TLC), spectroscopic (VIS, EIMS, FABMS, FABMSMS, 2D 1H NMR) and chemical evidence. The novel carotenoid end group exhibits particular spectroscopic and chemical properties. In particular the reactions with base and acid are investigated. Due to a very weak molecular ion upon electron impact and facile cleavage to paracentrone 20 related fragments, the new carotenoid was previously misidentified as 19′-hexanoyloxyparacentrone 3-acetate 8, also found in other prymnesiophytes (haptophytes). This novel carotenoid readily undergoes cleavage to a C31-skeletal paracentrone 20 related product upon storage, preferably in methanol solution. The new end group represents a plausible precursor for C31-skeletal methyl ketone apocarotenoid metabolites in animals, and differs from the previously suggested precursor. p