G. W. Patterson

Sterols ofChaetoceros andSkeletonema

Dietary sterol is required by the oyster for growth, and sterol is believed to be obtained primarily from dietary phytoplankton. Seven isolates ofChaetoceros and one ofSkeletonema, which are of potential use as oyster food, were analyzed for sterol composition using gas chromatography, high-performance liquid chromatography and gas chromatography/mass spectrometry.Skeletonema and five isolates ofChaetoceros contained cholesterol as their major sterol. Two other isolates ofChaetoceros also contained cholesterol, but 24-methylenecholesterol was the principal sterol. Cholesterol has rarely been reported as the major sterol from phytoplankton. In view of the widespread occurrence ofSkeletonema andChaetoceros in the marine environment, these algae could be an important source of the oysters cholesterol.

Effects of triparanol and AY-9944 upon sterol biosynthesis inChlorella

The growth rates of three species ofChlorella were inhibited by triparanol and AY-9944.Chlorella emersonii was noticeably more resistant to both inhibitors than the other species. A large number of sterols were isolated and identified in inhibited cultures. Ca. 18 of these were identified from nature for the first time. Triparanol resulted in inhibition of the removal of the 14α methyl group. It also inhibited the second alkylation of the side chain and, in one species, strongly inhibited the Δ8 → Δ7 isomerase reaction. InC. ellipsoidea, triparanol also inhibited Δ14-reductase and Δ7-reductase. The introduction of the Δ22 double bond was inhibited by both drugs. The effect of AY-9944 was similar to that of triparanol inC. emersonii, but it was an extremely effective Δ14-reductase inhibitor inC. ellipsoidea. These various types of inhibition of sterol synthesis indicate a lack of specificity of both drugs inChlorella and suggest that primitive plants such as these may be valuable as test organisms in an evaluation of the activity of potential inhibitors of sterol biosynthesis.

Sterols of Laminaria.

Abstract 1. 1. Fucosterol, 24-methylene cholesterol, cholesterol, saringosterol and, tentatively, desmosterol were identified in Laminaria faeroensis and L. digitata . 2. 2. Wtith the exception of choleserol, which is quantitatively a minor sterol, all the sterols were unsaturated in the side-chain. 3. 3. Laminaria is apparently unable to reduce the side-chains of these sterols to produce sterols common to other plants.

Sterols of scallop. III. Characterization of some C-24 epimeric sterols by high resolution (220 MHz) nuclear magnetic resonance spectroscopy

Alkyl sterols epimeric at C-24 isolated from the Atlantic scallop,Placopecten magellanicus, were analyzed by high resolution (220 MHz) nuclear magnetic resonance spectrometry, and their spectra compared with authentic samples. This technique was used to assign absolute stereochemistry in epimeric mixtures of 24 R and S 24-methylcholest-5-en-3β-ol, (22E)-24-methylcholesta-5,22-dien-3β-ol and 24-ethylcholest-5-en-3β-ol. It also allowed a semiquantitative estimate of the R/S isomers present in the mixture.

Sterols of eustigmatophytes.

The oyster cannot synthesize sterols from smaller molecules but must obtain them from its diet, which consists of detritus and small organisms, i.e., mostly single-celled algae. Algae differ widely in their effectiveness as oyster food. Small (<5 μm) algae which are abundant in sterols and polyunsaturated fatty acids appear to be most effective. Recent studies have shown the occurrence of cholesterol in strains of the unicellular algaeTetraselmis, Chaetoceros andSkeletonema, sometimes in large quantities. In the study reported here, six isolates of a recently constructed algal class, the Eustigmatophyceae, have been examined for sterols and fatty acids by gas chromatography and gas chromatography/mass spectrometry. All strains were shown to contain cholesterol as the principal sterol. Two isolates contained large amounts of total sterol (400–1000 fg/cell), and one (Sticho 0–18) also contained large amounts of eicosapentaenoic acid (20∶5n−3). These biochemical characteristics are desirable in a potential food source for oysters.

The occurrence of brassicasterol and epibrassicasterol in the chromophycota

Abstract 1. 1. Sterols were identified from eight isolates of five species in the Chromophycota that were cultured axenically and harvested in the stationary phase. 2. 2. Analyses were performed on four strains from the Prymnesiophyceae, two strains from the Cryptophyceae and one from the Bacillariophyceae. Most strains examined contained only one major sterol, 24-methyl-22-dehydrocholesterol. 3. 3. Analysis by capillary GC, HPLC, and in one instance NMR, showed that the two strains provisionally identified as Isochrysis contained brassicasterol (24β-methyl-22-dehydrocholesterol); whereas, all other species examined contained primarily epibrassicasterol (24α-methyl-22-dehydrocholesterol). 4. 4. Stigmasterol (24α-ethyl-22-dehydrocholesterol) accompanied epibrassicasterol in Pleurochrysis carterae. 5. 5. Analyses of C-24 alkyl isomers in these algae may provide useful information concerning their taxonomic placement. 6. 6. The occurrence of both isomers of 24-methyl-22-dehydrocholesterol in oysters is explained by the occurrence of both isomers among algae which are probably dietary sources for oysters.

Quantitative estimation of C-24 epimeric sterol mixtures by 220 MHz nuclear magnetic resonance spectroscopy

Four pairs of 24-alkyl epimeric sterols: 24α- and 24β-methylcholesterol; 24α- and 24β-ethylcholesterol; 24α- and 24β-methyl-5, 22-E-cholestadienol; and 24α- and 24β-ethyl-5, 22-E-cholestadienol, were mixed in known proportions (0, 20, 40, 50, 60, 80 and 100% of β-epimer to α-epimer). The 220 MHz nuclear magnetic resonance spectra of each of the mixtures were obtained and compared. Areas of these spectra useful in quantitative determinations were identified and discussed.

Unusual tetraene sterols in some phytoplankton

Sterols were analyzed from four phytoplankton strains which are under investigation as possible sources of food for oysters in culture. One strain ofPyramimonas contained only 24-methylenecholesterol as a major sterol component.Pyramimonas grossii, Chlorella autotrophica andDunaliella tertiolecta each contained a complex mixture of C28 and C29 sterols with Δ7, Δ5,7 and Δ5,7,9(11) nuclear double bond systems. Sterols were found both with and without the C-22 side chain double bond. Ergosterol and 7-dehydroporiferasterol were the principal sterols in each of the latter three species, which also contained the rare tetraene sterols, 24-methylcholesta-5,7,9(11),22-tetraen-3β-ol and 24-ethylcholesta-5,7,9(11),22-tetraen-3β-ol.

Sterols of Tetraselmis (Prasinophyceae)

Abstract 1. 1. Sterols were identified from 11 isolates of Tetraselmis , a unicellular Prasinophyte alga used frequently as food in mariculture. 2. 2. The principal sterol in eight isolates was either 24-methylenecholesterol or 24-methylcholesterol; the latter was determined to be campesterol in all cases. 3. 3. Campesterol is the first 24α sterol to be reported in the Prasinophyceae. 4. 4. In the remaining three isolates, cholesterol was the principal sterol with smaller amounts of 24-methylenecholesterol and campesterol present; in two of these strains total sterol approached 3% of dry weight. 5. 5. This is the first report of cholesterol as the principal sterol of a Prasinophyte; the C28 sterols found in Tetraselmis are the dominant sterols in most Prasinophyceae studied to date.

Metabolism of 2,4-3H-14α-methyl-5α-ergost-8-enol and 2,4-3H-5α-ergosta-8,14-dienol inChlorella ellipsoidea

Abstract5α-Ergosta-8,14-dienol and 14α-methyl-5α-ergost-8-enol were synthesized chemically from ergosterol and labeled with tritium at the C-2 and C-4 positions. Both labeled sterols, when incubated with growing cultures ofChlorella ellipsoidea, were converted to ergost-5-enol but not to C-27 or C-29 sterols.Chlorella ellipsoidea, thus, has the capability of removing the C-14 methyl group and converting the 8(9) and 8,14 double bond systems to the 5(6) position. Brassicasterol produced by this organism is not labeled in these experiments, indicating that it is not derived from a saturated side chain precusor.