Carbon-carbon bond cleavage of fucosterol-24, 28-oxide by cell-free extracts of silkworm Bombyx mori.

The 1500 X g supernatant of the silkworm $\text{Bombyx mori}$ gut homogenate catalyzed the conversion of 24, 28-epoxystigmast-5-en-3β-ol(III) to cholesta-5, 24-dien-3β-ol(IV) which is a key step of stigmast-5-en-3β-ol(I) dealkylation in the insects. A structural analog 24, 28-imino-stigmast-5-en-3β-ol(VI) was a potent inhibitor of this conversion.     

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 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).     

Biosynthesis of sitosterol in barley seedlings

A method is described for the chemical synthesis of stigmasta-5,24-dien-3β-ol-[26-¹⁴C] and (24S)-24-ethylcholesta-5,25-dien-3β-ol-[26-¹⁴C] (clerosterol). 28-Isofucosterol-[7-³H₂] fed to developing barley seedlings (Hordeum vulgare) was incorporated into sitosterol and stigmasterol confirming the utilisation of a 24-ethylidene sterol intermediate in 24α-ethyl sterol production in this plant. Also, the use of mevalonic acid-[2-¹⁴C(4R)-4-³H₁] verified the loss of the C-25 hydrogen of 28-isofucosterol during its conversion into sitosterol and stigmasterol in agreement with the previously postulated isomerisation of the 24-ethylidene sterol to a Δ²⁴⁽²⁵⁾-sterol prior to reduction. However, feeding stigmasta-5,24-dien-3β-ol [26-¹⁴C] to barley seedlings gave very low incorporation into sitosterol. Attempts to trap radioactivity from mevalonic-[2-¹⁴C(4R)-4-³H₁] in stigmasta-5,24-dien-3β-ol when this unlabelled sterol was administered to barley seedlings gave only a very small incorporation although both 28-isofucosterol and sitosterol were labelled.     

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.     

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.     

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.     

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 Xanthoria parietina: Evidence for two sterol ‘pools’ and the identification of a novel C,8 triene,ergosta-5,8,22-trien-3β-ol

Sterols extracted from Xanthoria parietina with organic solvents and released by saponification of the residual lichen tissue were analysed by GC-MS. The main components of the solvent-extractable sterols were two C₂₈ trienes and those of the more tightly bound sterols were ergost-5-en-3β-ol and two C₂₉ compounds. The structures of the C₂₈ compounds were shown to be ergosta-5,7,22-trien-3β-ol, Ia (ergosterol) and the previously unreported ergosta-5,8,22-trien-3β-ol, IIa, for which the name lichesterol is proposed. The main C₂₉ sterol was identified as (24R)-24-ethylcholesta-5,22-dien-3β-ol (poriferasterol).     

Free sterols of the red alga Gigartina skottsbergii

The free sterols of the red alga Gigartina skottsbergii have been identified by means of GC and GC/MS analyses. The mixture contained saturated and unsaturated C²⁷, C²⁸ and C²⁹ sterols. The major component was cholest-5-en-3β-ol. Cholesta-5,24-dien-3β-ol (desmosterol) was present in low proportion but no side chain hydroxylated components were detected.     

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 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.     

The inhibition of cholesterol biosynthesis in MRC-5 fibroblasts in culture by cholesta-5,7,9-trien-3β-ol

Cholesta-5,7,9-trienol-3β-ol is a potent inhibitor of cholesterol biosynthesis and the enzyme 3-hydroxy-3-methyl-glutaryl CoA reductase in MRC-5 fibroblasts in culture. A similar type of inhibition is not exhibited by cholesta-5,7-dien-3β-ol, cholesta-7,9-dien-3β-ol or cholesterol.     

Two new sterols from Chlorella ellipsoidea

Eight sterols were observed in Chlorella ellipsoidea and the four major components were identified as ergosterol, 5α-ergost-7-en-3β-ol, 22-trans-ergosta-5,8(9),22-trien-3β-ol and ergosta-5,8(9)-dien-3β-ol. This is the first report of the latter two sterols from green plants.     

A new saponin from seeds of Amoora rohituka

Phytochemical examination of the seeds of Amoora rohituka resulted in the isolation and identification of a new saponin, stigmasta-5,24(28)-dien-3β-O-β-d-glucopyranosyl-O-α-l-rhamnopyranoside.     

Sterols with 29, 28 and 27 carbon atoms metabolically related to cholesterol, occurring in developing and mature brain

Brain sterols from chick embryos (11 and 18 days of incubation) and mature rats, previously injected with [2-¹⁴C]mevalonate, were analysed. Acetate derivatives of the sterols were chromatographed on Silica Gel:Celite:AgNO₃ columns. Sterol fractions were assayed for radioactivity and the amounts determined by gas chromatography. Sterol structures were elucidated by gas chromatography-mass spectrometry. The method used allowed the identification of some sterols representing no more than 0-01 per cent of the total mixture. The following brain sterols were identified: cholesterol, cholestanol, cholest-5,24-dien-3β-ol (desmosterol); 4,4′-dimethyl-cholest-8-en-3β-ol, 4α-methyl-cholest-8-en-3β-ol, cholest-8-en-3β-ol, 4,4′-dimethyl-choIest-8,24-dien-3β-ol, 4α-methyl-cholest-8,24-dien-3β-ol, cholest-8,24-dien-3β-ol and cholest-7,24-dien-3β-ol. Small amounts of other sterols including polyhydroxy sterols, were also detected. There were no qualitative differences in the sterols detected in developing and mature brain. In the developing chick brain, cholesterol represented approximately 90 per cent of the total sterols. In the mature rat brain, cholesterol accounted for 98 per cent of the sterols. The adult rat brain, as well as the embryonic chick brain, demonstrated the capacity to incorporate mevalonate into cholesterol precursors and cholestanol. The sterols retaining the double bond in the lateral chain, that is, those of the Δ^8,24 series with 29, 28 and 27 carbon atoms and desmosterol, were highly labelled compared with the other identified intermediates. The possibility, supported by our data, that a preferential biosynthetic route for cholesterol exists in brain, is discussed.     

Sterol composition of Linneus torquatus (Nemertini) Anopla

The sterol fraction from the marine worm Linneus torquatus Coe (phylum Nemertini, class Anopla, family Lineidae) has been isolated, separated by HPLC and preparative TLC on AgNO₃-impregnated silica gel, and sterols identified using GC, GC-MS and NMR spectroscopy. It was shown that the fraction contains at least 12 sterols belonging mainly to Δ^5,22, Δ^5,24(28) and Δ⁵ series. The major sterol components were 24-methylcholesta-5,24(28)-dien-3β-ol, cholesta-5,22E-dien-3β-ol, 24-nor-cholesta-5,22-dien-3β-ol and cholesterol.     

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.     

Side chain-hydroxylated sterols of the red alga Asparagopsis armata: Significant products or artifacts due to autoxidation?

Sterols characterized by an allylic hydroxyl group in the side chain, such as stigmasta-5,28-diene-3 beta, 24 epsilon-diol (1), cholesta-5,23-diene-3 beta,25-diol (2) and cholesta-5,25-diene-3 beta,24 epsilon-diol (3), have been identified several times in various marine algae. Their origin was considered as doubtful: they could have been bona fide constituents of the alga, or be artifacts caused by autoxidation during the isolation process. We have shown that the dihydroxy steroids 2 and 3 can indeed be produced by the autoxidation of cholesta-5,24-dien-3 beta-ol (desmosterol) (5), but that they are nevertheless present in the taxonomic significance.     

Chemical profile of adults and buds of the chemically defended marine sponge Tethya maza

Several adults and the corresponding larvae of marine sponges are known as rich sources of secondary metabolites. In this paper we will show the chemical profile of adults and buds of the sponge Tethya maza. Cholesterol, ergost-5,22-dienol-3, stigmast-5,24-dienol-3, cholest-5,22-dienol-3, cholest-5-enol-3-one-7, and stigmast-5,24(28)-dien-3-ol were the major compounds detected, two of them being detected only in crude extracts of the adults while one was present only in the buds. Due to this high similarity it is supposed that buds could be chemically protected with regards to predation as well as the adult individuals of T. maza. This is the first report of chemicals present in the structures (buds) of sponges produced by asexual reproduction.