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).     

Minor and trace sterols in marine invertebrates V. isolation,structure elucidation and synthesis of 3β-hydroxy-26,27-bisnorcholest-5-en-24-one from the sponge Psammaplysilla Purpurea

The free sterol mixture of the sponge Psammaplysilla purpurea was shown to contain aplysterol as the major constituent. In addition to other sterols such as 5,7-cholestadien-3β-ol, cholesterol, 5α-cholestan-3β-ol, 24ε-methylcholesta-5,22-dien-3β-ol, 24ε-methylcholesterol, 24ε-ethylcholesta-5,22-dien-3β-ol and 24,28-dehydroaplysterol, a new minor sterol was isolated and shown by spectral analysis as well as partial synthesis to be 3β-hydroxy-26,27-bisnorcholest-5-en-24-one. The sterol mixture contains no other short side chain or 24-keto sterols except for small amounts of 3β-hydroxypregn-5-en-20-one and 3β-hydroxy-5α-pregnan-20-one.     

STEROLS OF 14 SPECIES OF MARINE DIATOMS (BACILLARIOPHYTA)1

The sterol compositions of 14 species of marine diatoms were determined by gas chromatography and gas chromatography-mass spectrometry. A variety of sterol profiles were found. The sterols 24-methylcholesta-5,22E-dien-3β-ol, cholest-5-en-3β-ol, and 24-methylcholesta-5,24(28)-dien-3β-ol, previously described as the most common sterols found in diatoms, were major sterols in only a few of the species. In light of this and other recent data, it is clear that these three sterols are not typical constituents of many diatom species. Most of the centric species examined had 24-methylcholesta-5,24(28)-dien-3β-ol and 24-methylcholest-5-en-3β-ol as two of their major sterols. The exception was Rhizosolenia setigera, which possessed cholesta-5,24-dien-3β-ol as its single major sterol. In contrast to the centric species, the pennate diatoms examined did not have any particular sterols common to most species. Minor levels ofΔ⁷-sterols, rarely found in large amounts in diatoms, were found in four species. C₂₉sterols were found in many species; seven contained 24-ethylcholest-5-en-3β-ol and three contained 24-ethylcholesta-5,22E-dien-3β-ol, reinforcing previous suggestions that C₂₉ sterols are not restricted to higher plants and macroalgae. 24-Ethylcholesta-5,22E-dien-3β-ol may prove to be useful for taxonomy of the genus Amphora and the order Thalassiophysales. A major sterol of Fragilaria pinnata was the uncommon algal sterol 23,24-dimethylcholesta-5,22E-dien-3β-ol. Cholesta-5,24-dien-3β-ol was the only sterol found in the culture of Nitzschia closterium. This differed from previous reports of 24-methylcholesta-5,22E-dien-3β-ol as the single major sterol in N. closterium. Two C₂₈ sterols possessing an unusual side chain were found in Thalassi-onema nitzschioides, a C_28:2 sterol (16%) and a C_28:1 sterol in lower abundance (2.5%), which may be 23-methylcholesta-5,22E-dien-3β-ol and 23-methyl-5α-cholest-22E-en-3β-ol, respectively. The species Cylindrotheca fusiformis, T. nitzschioides, and Skeletonema sp. may be useful as direct sources of cholesterol in mariculture feeds due to their moderate to high content of this sterol.     

Biosynthesis of Δ5.23 sterols in etiolated coleoptiles from Zea mays

In addition to the previously found ergosta-5, E-23-dien-3β-ol and 5α-ergosta-7, E-23-dien-3β-ol, the following Δ23 sterols have been identified in etiolated maize coleoptiles: cyclosadol, 4α, 14α-dimethyl-5α-ergosta-8, E-23-dien-3β-ol, 4α, 14α-dimethyl-9β, 19-cyclo-5α-ergosta-8, E-23-dien-3β-ol and 4α-methyl-5α-ergosta-7, E-23-dien-3β-ol. The incubation of maize coleoptile microsomes in the presence of cycloartenol and of [¹⁴C-methyl]S-adenosyl methionine gave a mixture of labelled 24-methylene cycloartanol and cyclosadol. No trace of cyclolaudenol could be detected in these conditions. It is suggested that Δ²³ sterols are products of the C-24 methyltransferase reaction and they probably do not arise from a Δ²⁴ → Δ²³ isomerization occurring at a later stage of the biosynthesis. The Δ¹³-sterols may play an intermediary role in the biosynthesis of 24-methyl sterols in this plant material.     

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.     

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.     

Investigations on the Δ23-, Δ24(28)- and Δ25-Sterols of zea mays

The sterols of Zea mays shoots were isolated and characterized by TLC, HPLC, GC/MS and ¹H NMR techniques. In all, 22 4-demethyl sterols were identified and they included trace amounts of the Δ²³-, Δ²⁴- and Δ²⁵-sterols, 24-methylcholesta-5,E-23-dien-3β-ol, 24-methylcholesta-5,Z-23-dien-3β-ol, 24-methylcholesta-5,25-dien-3β-ol, 24-ethylcholesta-5,25-dien-3β-ol and 24-ethylcholesta-5,24-dien-3β-ol. In the 4,4-dimethyl sterol fraction, cycloartenol and 24-methylenecycloartanol were the major sterol components but small amounts of the Δ²³-compound, cyclosadol, and the Δ²⁵-compound, cyclolaudenol, were recognized. These various Δ²³- and Δ²⁵-sterols may have some importance in alternative biosynthetic routes to the major sterols, particularly the 24β-methylcholest-5-en-3β-ol component of the C₂₈-sterols. Radioactivity from both [2-¹⁴C]MVA and [methyl-¹⁴C]methionine was incorporated by Z. mays shoots into the sterol mixture. Although 24-methylene and 24-ethylidene sterols were relatively highly labelled, the various Δ²³- and Δ²⁵-sterols contained much lower levels of radioactivity, which is possibly indicative of their participation in alternative sterol biosynthetic routes. (24R)-24-Ethylcholest-5-en-3β-ol (sitosterol) had a significantly higher specific activity than the 24-methylcholest-5-en-3β-ol indicating that the former is synthesized at a faster rate.     

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.     

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.     

Sterols of the lichen Pseudevernia furfuracea

A mixture of C₂₇, C₂₈ and C₂₉ sterols was isolated from the lichen Pseudevernia furfuracea and characterized by means of GLC and MS. Mono-, di- and tri-unsaturated sterols were identified as well as a small amount of fully saturated sterols (stanols). Only a part of the total sterols present in the lichen tissue was easily extractable with organic solvents. Another portion was only obtained after saponification of the lichen residue remaining after extraction with organic solvents. The composition of these two fractions difrered considerably, the former contained predominantly 5a,8a-epidioxy-5a-ergosta-6,22-dien-3β-ol (ergosterol peroxide) and 24-ethylcholesta-5,22-dien-3β-ol while in the latter 24-ethylcholesta-5,22-dien- 3β-ol and C₂₈ triene sterols were the main components.     

Dehydrodinosterol,dinosterone and related sterols of a non-photosynthetic dinoflagellate, Crypthecodinium cohnii

The heterotrophic dinoflagellate Crypthecodinium cohnii contained the 4α-methyl sterols, dinosterol, dehydrodinosterol (4α,23,24-trimethylcholesta-5,22-dien-3β-ol) and the tentatively identified 4α,24-dimethyl-cholestan-3β-ol and 4α,24-dimethylcholest-5-en-3β-ol. The major 4-demethyl sterol was cholesta-5,7-dien-3β-ol which was accompanied by a smaller amount of cholesterol and traces of several other C₂₇,C₂₈ and C₂₉ sterols. In addition, a 3-oxo-steroid fraction was isolated and the major component identified as dinosterone (4α,23,24-trimethylcholest-22-en-3-one). The possible biosynthetic relationships of these compounds are discussed.     

Effect of ay-9944 on sterol biosynthesis in Chlorella sorokiniana

When Chlorella sorokiniana was grown in the presence of 4 ppm AY-9944 total sterol production was unaltered in comparison to control cultures. However, inhibition of sterol biosynthesis was shown by the accumulation of a number of sterols which were considered to be intermediates in sterol biosynthesis. The sterols which were found in treated cultures were identified as cyclolaudenol, 4α,14α-dimethyl-9β,19-cyclo-5α-ergost-25-en-3β-ol, 4α,14α-dimethyl -5α-ergosta-8,25-dien-3β-ol, 14α-methyl-9β,19-cyclo-5α-ergost-25-en-3β-ol, 24-methylpollinastanol, 14α-methyl-5α-ergost-8-en-3β-ol, 5α-ergost -8(14)-enol, 5α-ergost-8-enol, 5α-ergosta-8(14),22-dienol, 5α-ergosta-8,22-dienol, 5α-ergosta-8,14-dienol, and 5α-ergosta-7,22-dienol, in addition to the normally occurring sterols which are ergosterol, 5α-ergost-7-enol, and ergosta-5,7-dienol.The occurrence of these sterols in the treated culture indicates that AY-9944 is an effective inhibitor of the Δ⁸ → Δ⁷ isomerase and Δ¹⁴-reductase, and also inhibits introduction of the Δ²²-double bond. The occurrence of 14α-dimethyl-5α-ergosta-8,25-dien-3β-ol and 14α-methyl-9β,19-cyclo-5α-ergost -25-en-3β-ol is reported for the first time in living organisms. The presence of 25-methylene sterols suggests that they, and not 24-methylene derivatives, are intermediates in the biosynthesis of sterols in C. sorokiniana.     

The identification of 24-methylene-24,25-dihydrolanosterol and other possible ergosterol precursors in Phycomyces blakesleeanus and Agaricus campestris

The following sterols have been isolated from the fungi, Phycomyces blakesleeanus and Agaricus campestris: ergosterol, lanosterol, 24-methylene-24,25-dihydrolanosterol and episterol. 4,4-Dimethyl-5α-ergosta-8.24(28)-dien-3β-ol and 4α-methyl-5α-ergosta-8,24(28)-dien-3β-ol have been tentatively identified. Evidence for the incorporation of label from l-methionine-[methyl-¹⁴C] into some of these sterols in P. blakesleeanus has been obtained. The significance of these sterols in ergosterol biosynthesis is discussed.     

Dinoflagellate sterols IV: Isolation and structure of 4α,23ξ,24ξ-trimethylcholestanol from the dinoflagellate Glenodiniumhallii

The dinoflagellate $\text{Glenodinium}$$\text{hallii}$ was investigated for its sterol composition. Five of the six sterols were isolated and identified as cholest-5-en-3β-ol, (24ξ)-24-methylcholest-5-en-3β-ol, stigmasta-5,22-dien-3β-ol, (22E,24R)-4α,23,24-trimethyl-5α-cholest-22-en-3β-ol, and 4α,23ξ,24ξ-trimethyl-5α-cholestan-3β-ol.     

Effect of fenarimol 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 fenarimol, 14α-methyl sterols accumulated. Eight 14α-methyl sterols, including two new compounds, 4α,14α-dimethyl-stigmasta-8,Z-24(28)-dien-3β-ol and 14α-methyl-stigmasta-8,Z-24(28)-dien-3β-ol, were identified. Fenarimol probably inhibited the 14α-methyl demethylation. Cell lines growing permanently in 2 fenarimol-supplemented medium were obtained.     

Sterols of the unicellular algae Nematochrysopsis roscoffensis and Chrysotila lamellosa: isolation of (24E)-24-n-propylidenecholesterol and 24-n-propylcholesterol

Two rare C₃₀-sterols, (24E)-24-n-propylidenecholest-5-en-3β-ol and 24-n-propylcholest-5-en-3β-ol, and (24S)-24-ethylcholesta-5,22-dien- 3β-ol (stigmasterol) are the major sterols of Nematochrysopsis roscoffensis, a Chrysophyte of the Sarcinochrysidales order. This unique sterol composition is different from the sterol contents of other Chrysophytes and justifies the peculiar position of the Sarcinochrysidales, which are by some characteristics morphologically and biologically related to the Phaeophyceae. The presence of (24S)-24-methylcholesta-5,22-dien-3β-ol (24-epibrassicasterol) as a major sterol in Chrysotila lamellosa is in accordance with the few previous results obtained from other Prymnesiophyceae, although the presence of the other major sterol, (24R)-24-ethylcholesta-5,22-dien-3β-ol (poriferasterol) has never been reported in these algae.     

硬孔灵芝的化学成分研究

采用硅胶柱层析法进行分离纯化,从硬孔灵芝Ganoderma duropora的氯仿萃取物中分离得到甾类化合物8种。根据波谱数据,化合物1-8结构分别被鉴定为:麦角甾醇、麦角甾-7,22-二烯-3β-醇、麦角甾-7,22-二烯-3-酮、6,9-环氧麦角甾-7,22-二烯-3β-醇、过氧麦角甾醇、3,5-二羟基麦角甾-7,22-二烯-6-酮、β-谷甾醇和胡萝卜苷。     

The occurrence of C29 sterols with different configurations at C-24 in Cucurbita Pepo as shown by 270 MHz NMR

The 270MHz NMR spectra of the major sterols of pumpkin seeds show that the configuration at C-24 of 24-ethyl-5α-cholesta-7,22,25-trien-3β-ol and 24-ethyl-5α-cholesta-7,25-dien-3β-ol is 24β_F = (24S) whereas the α-spinasterol has the 24α_F = (24S) configuration.     

Detection of the ergosterol and episterol isomers lichesterol and fecosterol in nystatin-resistant mutants of Neurospora crassa

Wild-type Neurospora crassa is completely inhibited by 5 ppm nystatin. Ultraviolet-induced mutants have been isolated that grow in the presence of 60 ppm of the antibiotic. Gas-liquid chromatographic, mass spectroscopic, and nuclear magnetic resonance analyses showed the wild-type sterols to be ergosterol (ergosta-5,7,22-trien-3β-ol) and episterol (ergosta-7,24(28)-dien-3β-ol) in a 3:1 ratio. The mutants contained lichesterol (ergosta-5,8,22-trien-3β-ol) and fecosterol (ergosta-8,24(28)-dien-3β-ol) in a 2:1 ratio, differing from the wild type only in the position of the B-ring unsaturation. A deficiency of an ergosta-8,24 (28)-dien-3β-ol:ergosta-7,24(28)-dien-3β-ol isomerase is indicated.     

Sterols of morphologically distinct,okadaic acid-producing Prorocentrum texanum var. texanum and var. cuspidatum isolated from the Gulf of Mexico

Prorocentrum texanum var. texanum and its morphologically distinct yet genetically identical (as based on the sequences of five genes) variety P. texanum var. cuspidatum represent a species of Prorocentrum recently isolated from the Gulf of Mexico. Together, these two varieties represent a sister species to Prorocentrum micans. P. micans has had its sterols, which are ringed lipids common to eukaryotic cell membranes, shown in some studies to be comprised of cholesterol (cholest-5-en-3β-ol), 23,24-dimethyl-cholesta-5,22-dien-3β-ol, 23,24-dimethyl-5α-cholest-22E-en-3β-ol, dinosterol, and 4α,23,24-trimethyl-5α-cholestan-3β-ol (dinostanol) as major sterols, thus placing it within a previously identified cluster of dinoflagellates characterized by the predominance of cholesterol and dinosterol. In this study we have determined the sterol compositions of these two varieties of P. texanum to be abundant in cholesterol, 23,24-dimethyl-cholesta-5,22-dien-3β-ol, 23,24-dimethyl-5α-cholest-22E-en-3β-ol, dinosterol, and dinostanol such that the varieties are virtually indistinguishable from each other, making them both in general agreement with the sterols of P. micans, its closest species relative. This expands our knowledge of the sterols of this environmentally important dinoflagellate genus.