The fatty acid and sterol composition of two marine dinoflagellates

The fatty acid, sterol and chlorophyll pigment compositions of the marine dinoflagellates Gymnodinium wilczeki and Prorocentrum cordatum are reported. The fatty acids of both algae show a typical dinoflagellate distribution pattern with a predominance of C₁₈, C₂₀ and C₂₂ unsaturated components. The acid 18:5ω3 is present at high concentration in these two dinoflagellates. G. wilczeki contains a high proportion (93.4%) of 4-methyl-5α-stanols including 4,23,24-trimethyl-5α-cholest-22E-en-3β-ol (dinosterol), dinostanol and 4,23,24-trimethyl-5α-cholest-7-en-3β-ol reported for the first time in dinoflagellates. The role of this sterol in the biosynthesis of 5α-stanols in dinoflagellates is discussed. P. cordatum contains high concentrations of a number of δ ²⁴⁽²⁸⁾-sterols with dinosterol, 24-methylcholesta-5,24(28)-dien-3β-ol, 23,24-dimethylcholesta-5,22E-dien-3β-ol, 4,24-dimethyl-5α-cholest-24(28)-en-3β-ol and a sterol identified as either 4,23,24-trimethyl- or 4-methyl-24-ethyl-5α-cholest-24(28)-en-3β-ol present as the five major components. The role of marine dinoflagellates in the input of both 4-methyl- and 4-desmethyl-5α-stanols to marine sediments is discussed.     

Sterols and fatty acids of the marine diatom biddulphia sinensis

Nine sterols, most showing Δ⁵- or Δ^5,22-unsaturation, were identified in the marine diatom Biddulphia sinensis. One sterol, cholesta-5,22E-dien-3β-ol, comprised 70–80% of the total sterols which is the first such predominance noted in a diatom. The only Δ⁷-sterol detected was cholest-7-en-3β-ol and this was a very minor component. A sterol showing unusual side-chain alkylation,23,24-dimethylcholesta-5,22E-dien-3β-ol, was identified for the first time in a diatom. Total fatty acids exhibited a predominance of Δ⁹- 16:1, 14:0, 20:5 and 16:0, typical of diatoms, although the proportions of these acids were found to vary with culture maturity. n-Heneicosahexaene was the major hydrocarbon together with a small amount of squalene.     

Lipids of the antarctic sea ice diatom Nitzschia cylindrus

The sterol and neutral, glyco- and phospholipid fatty acid profiles of the sea ice diatom Nitzschia cylindrus, isolated from McMurdo Sound, Antarctica, are reported. Two sterols were detected, trans-22-dehydrocholesterol (66% of total sterols) and cholesterol (34%); no sterols containing alkyl groups at the C₂₄ position were present. The major fatty acids in N. cylindrus, 16:1Δ9c, 14:0, 16:0, 20:5Δ5,8,11,14,17 and 20:4Δ5,8,11,14, were typical of previous reports of diatom fatty acids. A number of long-chain monounsaturated fatty acids were also detected, with higher relative proportions present in the phospholipid fraction. GC-MS analysis of the dimethyldisulphide adducts of these monounsaturated components showed that 24: 1Δ13c, 24:1Δ15c, 26:1Δ15c and 26:1Δ17c were the major components. The distribution of these fatty acids suggests that chain elongation of monounsaturated fatty acids was occurring in N. cylindrus. The proposed chain lengthening occurring for N. cylindrus represents, to our knowledge, the first report of possible chain lengthening of monounsaturated fatty acids in microscopic algae. These features, the presence of long-chain monounsaturated fatty acids and the sterol profile, may allow the input of this alga into benthic marine sediments or food webs to be monitored.     

Lipids of the tropical seagrass Thallassia hemprichii

The component sterols, alcohols, hydrocarbons, monocarboxylic, α,ω-dicarboxylic and α- and ω-hydroxy acids from the leaves and roots of the tropical seagrass Thallassia hemprichii are reported. The leaves contained significant concentrations of cholest-5-en-3β-ol, a sterol not normally detected in either higher plants or seagrasses. The lower abundance of polyunsaturated fatty acids found in both the leaves and roots compared to other seagrass species may be a result of the warmer waters from which this species was collected. Solvent-extractable, long-chain (> C₂₂)α,ω-diacids, α- and ω-hydroxy and monocarboxylic acids were also isolated from the leaves. The distribution pattern of these lipids should enable these components along with other distinctive components to be used as chemical markers for this seagrass.     

Metabolic engineering of omega-3 long-chain polyunsaturated fatty acids in plants using an acyl-CoA Δ6-desaturase with ω3-preference from the marine microalga Micromonas pusilla

Long-chain (≥C₂₀) polyunsaturated fatty acids (LC-PUFA) EPA and DHA (20:5^{Δ5,8,11,14,17} and 22:6^{Δ4,7,10,13,16,19}) have well-documented health benefits against coronary heart disease, rheumatoid arthritis and other disorders. Currently, the predominant sources of these fatty acids are marine fish and algal oils, but research is being conducted to ensure that a sustainable, land-based production system can be developed. We here describe the metabolic engineering of an artificial pathway that produces 26% EPA in leaf triacylglycerol using a newly-identified Δ6-desaturase from the marine microalga Micromonas pusilla. We also demonstrate that this enzyme appears to function as an acyl-CoA desaturase that has preference for ω3 substrates both in planta and in yeast. Phylogenetic analysis indicates that this desaturase shares highly conserved motifs with previously described acyl-CoA Δ6-desaturases.     

Dominance of Δ5-sterols in eight species of the cactaceae

The sterols from eight species in seven genera of the Cactaceae are 24-alkyl-Δ⁵-sterols. In all eight species, Echinopsis tubiflora, Pereskia aculeata, Hylocereus undatus, Notocactus scopa, Epiphyllum sp., Schlumbergera bridgesii, Opuntia comonduensis and O. humifusa, the dominant sterol is sitosterol (24α-ethylcholest-5-en-3β-ol) at 66–87% of the total sterol composition with the 24ξ-methylcholest-5-en-3β-ol present at 8–33%. Stigmasterol (24α-ethylcholesta-5,22E-dien-3β-ol) is present at 2–8% of the total sterol in P. aculeata, H. undatus, N. scopa and Epiphyllum sp. whereas cholesterol (cholest-5-en-3β-ol) is present in six species at levels of <0.1–5.0%. Avenasterol (24-ethylcholesta-7,24(28)Z-dien-3/gb-ol) and sitostanol (24α-ethyl-5α-cholestan-3β-ol) are each present in two species.     

Sterols of Agarum cribosum: desmosterol in a brown alga

The sterol composition of the cold water brown alga Agarum cribosum was determined by GC—MS. Six of the seven sterols found were identified as stigmata-5,(E)-24(28)-dien-3β-ol (fucosterol), 24-methylenecholest-5-en-3β-ol (24-methylenecholesterol), cholest-5-en-3β-ol (cholesterol), 3β-hydroxycholest-5-en-24-one (24-ketocholesterol), 24ξ-stigmasta-5,28-diene-3β,24-diol (saringosterol) and cholesta-5, 24-dien-3β-ol (desmosterol).     

Configuration at C-24 of sterols from the liverwort Palavicinnia lyellii

The 4-desmethylsterol fraction of the liverwort Palavicinnia lyellii is composed of 36% 24β-methylcholest-5-en-3β-ol (dihydrobrassicasterol), 16% 24α-methylcholest-5-en-3β-ol (campesterol), 33% 24α-ethylcholest-5-en-3β-ol (sitosterol) and 15% 24ξ-ethylcholesta-5,22-dien-3β-ol.     

Novel dinoflagellate 4α-methylated sterols from four caribbean gorgonians

Fourteen 4α-methyl sterols have been isolated from the gorgonians Briareum asbestinum, Gorgonia mariae, Muriceopsis flavida and Pseudoplexaura wagenaari, including the following five new sterols: 4α-methyl-24-methylene-5α-cholestan-3β-ol, (24R)-4α, 24-dimethyl-5α-cholesta-7,22-dien-3,β-ol, 4α,24S(or 23ξ)-dimethyl-5α-cholest-7-en-3β-ol, (22E, 24R)-4α,23,24-trimethyl-5α-cholesta-7,22-dien-3β-ol and (24R)-4α,24-dimethyl-5α-cholesta-8(14),22-dien-3β-ol. There is strong evidence that these 4α-methyl sterols are synthesized by the algal (dinoflagellate) symbionts (zooxanthellae) of the gorgonians. It is suggested that analysis of 4Δ-methyl sterol mixtures isolated from a zooxanthellae-bearing invertebrate, collected in several different geographic locations, might give information on the specificity of the symbiotic association between a given animal species and a particular strain of zooxanthellae.     

Separation of the pentacyclic triterpenes tylolupenols A and B from Tylophora kerrii

Tylolupenols A and B from Tylophora kerrii were separated and identified as D:C-friedolup-8(9)-en-3β-ol and D:C-friedolup-9(11)-en-3β-ol, respectively.     

Two serratane triterpenes from the stem bark of Picea jezoensis var. hondoensis

Two serratane triterpenoids were isolated from the stem bark of Picea jezoenis var. hondoensis, together with two known compounds, 3β-methoxyserrat-14-en-21-one and 3β-methoxyserrat-14-en-21α-ol. The serratane triterpenoids were characterized as 14β,15β-epoxy-3α-methoxyserratan-21β-ol and 3α-methoxy-21β-hydroxyserrat-14-en-16-one, on the basis of chemical and spectroscopic evidence.     

Sterols and fatty acids of the red tide flagellates Heterosigma akashiwo and Chattonella antiqua (Raphidophyceae)

The fatty acids and sterols of the raphidophyte flagellates, Heterosigma akashiwo (Australian and Plymouth strains) and Chattonella antiqua (Japanese strain) are reported. The major sterol of both species is 24-ethylcholesterol, which is more commonly associated with higher plants and has rarely been reported in unicellular algae. C. antiqua also contained 24-dihydrozymosterol [cholest-8(9)-en-3β-ol], which is also uncommon in marine algae. The major fatty acids in both raphidophytes are 16:0, 18:4ω3, 20:5ω3, 16:1ω7 and 14:0. Polyunsaturated fatty acids accounted for 46–50% of the total fatty acids in both species. The fatty acid 18:5ω3 was detected in H. akashiwo, but not in C. antiqua. This acid is found in some dinoflagellates and Prymnesiophycean algae, but this is the first report of its presence in the Raphidophyceae. The lipid distributions obtained for H. akashiwo and C. antiqua provide unique signature profiles for use in taxonomic, food-web and organic geochemical studies. The fatty acid and sterol distributions of these two raphidophytes justify their assignment to a separate class within the ‘brown algal’ line.     

Effect of AY-9944 on sterol biosynthesis in suspension cultures of bramble cells

Bramble suspension cultures normally contain Δ⁵ sterols (sitosterol, campesterol, and isofucosterol). When the cells were grown in a medium supplemented with AY-9944, their content of Δ⁵ sterols was greatly decreased and Δ⁸ sterols accumulated. Six Δ⁸ sterols, including three new compounds, (24R)-24-ethyl-5α-cholest-8-en-3β-ol, stigmasta-8,Z-24(28)-dien-3β-ol, and 4α-methyl-stigmasta-8,Z-24(28)-dien-3β-ol, were identified. AY-9944 probably inhibited the Δ⁸→Δ⁷ isomerase. A stable cell line growing permanently in an AY-supplemented medium was obtained.     

Free sterols,steryl esters,glucosides, acylated glucosides and water-soluble complexes in Calendula officinalis

In 3- and 14-day-old seedlings and in the leaves of Calendula officinalis the following sterols were identified: cholestanol, campestanol, stigmastanol, cholest-7-en-3-β-ol, 24-methylcholest-7-en-3β-ol, stigmast-7-en-3β-ol, cholesterol, campesterol, sitosterol, 24-methylcholesta-5,22-dien-3β-ol, 24-methylenecholesterol, stigmasterol and clerosterol. Sitosterol was predominant in young and stigmasterol in old tissues. Young tissues contained relatively more campesterol but in old tissues a C₂₈Δ^5,22 diene was present suggesting transformation of campesterol to its Δ^5,22 analog, similar to that of sitosterol to stigmasterol. All the identified sterols were present as free compounds and also in the steryl esters, glucosides, acylated glucosides and water-soluble complexes. The variations in the amounts of these fractions in the embryo axes and cotyledons of 3- and 14-day-old seedlings and the distribution of individual sterols among the fractions are discussed.     

Analysis of sterols in selected bloom-forming algae in China

Sterols, a group of stable lipid compounds, are often used as biomarkers in marine biogeochemical studies to indicate sources of organic matter. In this study, sterols in 13 species of major bloom-forming algae in China, which belong to Dinophyceae, Bacillariophyceae, Ulvophyceae, and Pelagophyceae, were analyzed with gas chromatography-mass spectrometry (GC–MS) to test their feasibility in representing different types of harmful algal blooms (HABs). It was found that (24Z)-stigmasta-5,24-dien-3β-ol (28-isofucosterol) was a major sterol component in green-tide forming macroalga Ulva prolifera. In bloom-forming dinoflagellates Alexandrium spp., Prorocentrum micans and Scrippsiella trochoidea, (22E)-4α,23-dimethyl-5α-ergost-22-en-3β-ol (dinosterol) was detected in addition to cholest-5-en-3β-ol (cholesterol), (22E)-ergosta-5,22-dien-3β-ol, (22E)-stigmasta-5,22-dien-3β-ol and other minor sterol components. In brown-tide forming pelagophyte Aureococcus anophagefferens, (24E)-24-propylcholesta-5,24-dien-3β-ol ((24E)-24-propylidenecholesterol) and (24Z)-24-propylcholesta-5,24-dien-3β-ol ((24Z)-24-propylidenecholesterol) were detected together with cholesterol, (22E)-stigmasta-5,22-dien-3β-ol, stigmast-5-en-3β-ol and campest-5-en-3β-ol. Among the selected bloom-forming diatoms, Chaetoceros sp. and Pseudo-nitzschia spp. only produced cholesterol, while Cylindrotheca closterium produced solely (22E)-ergosta-5,22-dien-3β-ol. Sterol content in four bloom-forming algal species correlates well with their biomass or abundance. It's proposed that 28-isofucosterol could serve as a promising biomarker for green algae in green-tide studies. Dinosterol and (24Z)-24-propylidenecholesterol can be used as potential biomarkers to represent bloom-forming dinoflagellates and pelagophytes, while (22E)-ergosta-5,22-dien-3β-ol is not a good indicator for diatoms.     

Fatty acid and sterol compositions in mushrooms of ten species of polyporaceae

The simple lipids present in ten species of Polyporaceae (Piptororus betulinus, Coriolus pargamenus, C. versicolor, C. heteromorphus, Formitopsis cytisina, F. pinicola, Microporus flabelliformis, Gloephyllum saepiarium, Crytoderma citrinum and Grifola frondosa) were investigated. The fatty acids that these species had in common were C₁₆-saturated acids (except in P. betulinus) and C₁₈-unsaturated acids. Ergosterol and ergosta-7,22-dien-3β-ol were isolated from these mushrooms. Lupeol was obtained from G. saepiarium. Ergost-7-en-3β-ol, lanosterol and 24-methylene-24,25-dihydrolanosterol were tentatively identified.     

Sterols and fatty acids of an antarctic sea ice diatom, Stauroneis amphioxys

Unialgal clonal cultures of the diatom Stauroneis amphioxys Gregory, isolated from sea ice of the Indian Ocean sector ofthe Southern Ocean, were grown at 3° and 20°. The relative abundances offatty acids, sterols and phytol for the two cultures are comparable. The two sterols observed [24-methylcholesta-5,22E-dien-3β-ol (79%) and cholesterol (21%)] did not vary with culture temperature. The-major fatty acid composition is typical ofmost diatoms. A pronounced change of ratio with temperature occurred with the pair 16:4 Δ6, 9, 12, 15 and 16:3 Δ6, 9, 12 followed by 18:4 Δ6, 9, 12, 15:18:3 Δ9,12,15 and 20:5 Δ5,8,11,14,17:20:4 Δ8,11,14,17; thus the relative abundances of 16:4, 18:4, 20:5 and 22:6 increase at the lower growth temperature. The total amounts of unsaturated acids do not change with temperature suggesting an effect on the final desaturase step. No cryoprotective role for such changes in lipid composition was inferred.     

PIGMENTS,FATTY ACIDS,AND STEROLS OF THE TOXIC DINOFLAGELLATE GYMNODINIUM CATENATUM1

Cultures and field samples of the toxic dinoflagellate Gymnodinium catenatum Graham from Tasmania, Australia, were analyzed for pigment, fatty acid, and sterol composition. Gymnodinium catenatum contained the characteristic pigments of photosynthetic dinoflagellates, including chlorophyll a, chlorophyll c₂, and the carotenoids peridinin, dinoxanthin, diadinoxanthin, diatoxanthin, and β,β-carotene. In midlogarithmic and early stationary phase cultures, the chlorophyll a content ranged 50–72 pg · cell^?1, total lipids 956–2084 pg · cell^?1, total fatty acids 426–804 pg · cell^?1, and total sterols 8–20 pg · cell^?1. The major fatty acids (in order of decreasing abundance) were 16:0, 22:6(n-3), and 20:5(n-3) (collectively 65–70% of the total fatty acids), followed by 16:1(n-7), 18:2(n-6), and 14:0. This distribution is characteristic of most dinoflagellates, except for the low abundance (<3%) of the fatty acid 18:5(n-3), considered by some authors to be a marker for dinoflagellates. The three major sterols were 4α-methyl-5α-cholest-7-en-3β-ol, 4α,23,24-trimethyl-5α-cholest-22E-en-3β-ol (the dinoflagellate sterol, dinosterol), and 4α,23,24-trimethyl-5α-cholest-7-en-3β-ol. These three sterols comprised about 75% of the total sterols in both logarithmic and early stationary phase cultures, and they were also found in high proportions (22–25%) in natural dinoflagellate bloom samples. 4-Desmethyl sterols, which are common in most microalgae, were only present in trace amounts in G. catenatum. The chemotaxonomic affinities of G. catenatum and the potential for using specific signature lipids for monitoring toxic dinoflagellate blooms are discussed.     

Inhibitory effects of steroidal allenes on growth,development, and steroid metabolism of the silkworm,Bombyx mori

Steroidal allenes, stigmasta-5,24(28),28-trien-3β-ol (allene-I) and cholesta-5,23,24-trien-3β-ol (allene-II), were tested for their inhibitory effects on growth, development, and steroid metabolism in the silkworm, Bombyx mori. The allenic analogue (I) of stigmasta-5,24(28)-dien-3β-ol (2) was found to be a specific inhibitor for the conversion of stigmast-5-en-3β-ol (1) to stigmasta-5, 24(28)-dien-3β-ol (2) and/or stigmasta-5,24(28)-dien-3β-ol (2) to 24,28-epoxy-stigmast-5-en-3β-ol (3) This inhibitor held the larvae in the second instar for more than 20 days without developing to the third instar, when administered alone or with the dietary sterols of stigmast-5-en-3β-ol (1) or stigmasta-5,24(28)-dien-3β-ol (2). The second allene (II) with a similar structure to cholesta-5,24-dien-3β-ol (4) was also found to be an inhibitor for insect growth and development, but it appeared not to be acting via inhibition of sterol dealkylation.     

An alternative to fish oils: Metabolic engineering of oil-seed crops to produce omega-3 long chain polyunsaturated fatty acids

It is now accepted that omega-3 polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA; 20:5Δ5,8,11,14,17) and docosahexaenoic acid (DHA, 22:6Δ4,7,10,13,16,19) play important roles in a number of aspects of human health, with marine fish rich in these beneficial fatty acids our primary dietary source. However, over-fishing and concerns about pollution of the marine environment indicate a need to develop alternative, sustainable sources of very long chain polyunsaturated fatty acids (VLC-PUFAs) such as EPA and DHA. A number of different strategies have been considered, with one of the most promising being transgenic plants “reverse-engineered” to produce these so-called fish oils. Considerable progress has been made towards this goal and in this review we will outline the recent achievements in demonstrating the production of omega-3 VLC-PUFAs in transgenic plants. We will also consider how these enriched oils will allow the development of nutritionally-enhanced food products, suitable either for direct human ingestion or for use as an animal feedstuff. In particular, the requirements of aquaculture for omega-3 VLC-PUFAs will act as a strong driver for the development of such products. In addition, biotechnological research on the synthesis of VLC-PUFAs has provided new insights into the complexities of acyl-channelling and triacylglycerol biosynthesis in higher plants.