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 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.     

The sterols of Argania spinosa seed oil

The sterol fraction of Argan seed oil (Argania spinosa) contains two main compounds, 5α-stigmast-7-en-3β-ol (schottenol) and 5α-stigmast-7,22(E)-dien-3β-ol (spinasterol).     

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.     

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.     

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 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.     

Triterpenes from Douglas fir sapwood

The saponified ether-soluble extractives of Douglas fir sapwood contained (24R)- 4α,14α,24-trimethyl-9β,19-cyclo-5α-cholestan-3β-ol(24R-cyclocucalanol),a new natural product; 4α,14α-dimethyl-9β,19-cyclo-24-methylene-5α-cholestan-3β- ol (cycloeucalenol); and (24R)-4α,24-dimethyl-5α-cholest-7-en-3β-ol (24R- methyllophenol); this is the first time they have been reported from Douglas fir.     

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.     

(22E,24S)-5α-Ergosta-7, 22-dien-3β-ol from the seeds of Cucumis sativus

(22E,24S)-5α-Ergosta-7,22-dien-3β-ol isolated from the seeds of Cucumis sativus was shown to be the 24S-epimer, i.e. stellasterol,     

Sesquiterpenoids from Pilea cavaleriei subsp. crenata

Three new humulane-type sesquiterpenes, 8-O-(p-coumaroyl)-5β-hydroperoxy-1(10)E,4(15)-humuladien-8α-ol (1), 8-O-(3-nitro-p-coumaroyl)-1(10)E,4(15)-humuladien-5β,8α-diol (2) and 8-O-(p-coumaroyl)-1(10)E,4(5)E-humuladien-8-ol (3), and a new copaborneol derivative, 1-O-p-coumaroyl-copaborneol (4), have been isolated from the methanol extract of Pilea cavaleriei Lévl. subsp. crenata C. J. Chen. Their structures were elucidated using spectroscopic methods. Cytotoxic and antimicrobial activities of the isolated compounds were evaluated.     

Alkaloids of erythroxylum macrocarpum and E. sideroxyloides

Erythroxylum macrocarpum and E. sideroxyloides, two closely related species indigenous to Mauritius, contain a similar range of alkaloids consisting mainly of benzoyl esters of tropan-3α-ol, tropan-3β-ol, and tropan-3α,6β-diol together with their nor-derivatives. 3α-Benzoyloxytropan-6β-ol (E. sideroxyloides) and 3α-benzoyloxynortropane and 3β-benzoyloxynortropan-6β-ol (both species) are reported for the first time.     

Behavioral responses of <Emphasis Type="Italic">Hyalesthes obsoletus</Emphasis> to host-plant volatiles cues

The polyphagous planthopper Hyalesthes obsoletus Signoret is considered to be the principal vector of stolbur phytoplasma, which is associated with yellow diseases of grapevine. To explore the possibility of developing novel control strategies, the behavioral responses to six synthetic mixtures and nine single compounds, previously identified from the headspace of Vitex agnus-castus L. (chaste tree) and Urtica dioica L. (nettle), were investigated in Y-tube bioassays. Choice tests revealed differences in the behavioral responses of males and females to the volatiles that they were exposed to. Males were attracted to a mixture containing (E)-β-caryophyllene, 1,8-cineole, (E,E)-α-farnesene, (E)-β-farnesene, and methyl salicylate (mixture 2). The addition of methyl benzoate to this five-compound mixture (mixture 3) did not attract males but elicited positive responses in females. Furthermore, females were attracted to a mixture containing (E)-β-caryophyllene, (E,E)-α-farnesene, (Z)-3-hexenyl acetate, (Z)-3-hexen-1-ol, and benzothiazole (mixture 4), but here addition of methyl salicylate (mixture 5) did not attract females. Neither males nor females showed attractivity or repellency toward the singly tested compounds. This study enhances knowledge on the interaction of insect behaviorally effective constituents in complex plant volatile mixtures. The attractive mixtures of plant volatiles identified suggest the possibility of using them in monitoring and management of H. obsoletus.     

Steroidal saponins of Asparagus curillus

Three spirostanol and two furostanol glycosides were isolated from a methanol extract of the roots of Asparagus curillus and characterized as 3-O-[α-l-arabinopyranosyl (1→4)- β-d-glucopyranosyl]-(25S)-5β-spirostan-3β-ol, 3-O-[{α-l-rhamnopyranosyl (1→2)} {α-l-arabinopyranosyl (1→4)}-β-d-glucopyranosyl]-(25S)-5β-spirostan- 3β-ol, 3-O-[{β-d-glucopyranosyl (1→2)} {α-l-arabinopyranosyl (1→4)}-β- d-glucopyranosyl]-(25S)-5β-spirostan-3β-ol, 3-O-[{β-d-glucopyranosyl (1→2)} {α-l-arabinopyranosyl (1→4)}-β-d-glucopyranosyl]-26-O-[β-d-glucopyranosyl]- 22α-methoxy-(25S)-5β-furostan-3β, 26-diol and 3-O-[{β-d-glucopyranosyl (1→2)} {α-l-arabinopyranosyl (1→4)}-β-d-glucopyranosyl]-26-O-[β-d-glucopyranosyl]- (25S)-5β-furostan-3β, 22α, 26-triol respectively.     

Configurational studies on red algae carotenoids

The configurations of (6′R)-β,ε-carotene, (3′R,6′R)-β,ε-caroten-3′-ol (α-cryptoxanthin), (3R,3′R,6′R)-β,ε-carotene-3,3′-diol (lutein), (3R)-β,β-caroten-3-ol (β-cryptoxanthin), (3R,3′R)-β,β-carotene-3,3′-diol (zeaxanthin) and all-trans (3S,5R,6S,3′R)-5,6-epoxy-5,6-dihydro-β,β-carotene-3,3′-diol (antheraxanthin) were established by CD and ¹H NMR studies. The red algal carotenoids consequently possessed chiralities at each chiral center (C-3, C-5, C-6, C-3′, C-6′), corresponding to the chiralities established for the same carotenoids in higher plants. Two post mortem artifacts from Erythrotrichia carnea were assigned the chiral structures (3S,5R,8R,3′R)-5,8-epoxy-5,8-dihydro-β,β-carotene-3,3′-diol [(8R)-mutatoxanthin] and (3S,5R,8S,3′R)-5,8-epoxy-5,8-dihydro-β,β-carotene-3,3′-diol [(8S)-mutatoxanthin]. This is the first well documented report of a naturally occurring β,ε-caroten-3′-ol (¹H NMR, CD, chemical derivatization).     

The conversion of (24S)-24-ethylcholesta-5,22,25-trien-3β-ol into poriferasterol,both in vivo and with a cell-free homogenate of the alga Trebouxia sp.

[6-³H₁] (24S)-24-Ethylcholesta-5,22,25-trien-3β-ol added to the growth medium of a culture of Trebouxia sp. 213/3 was efficiently taken-up by the cells and converted into (24R)-24-ethylcholesta-5,22-dien-3β-ol (poriferasterol) which is one of the major sterols of this alga. A cell-free homogenate was obtained from Trebouxia which catalysed the NADPH-dependent reduction of [6-³H₁] (24S)-24-ethylcholesta-5,22,25-trien-3β-ol to yield poriferasterol. The δ²⁵-sterol reductase was found to be mainly localized in the microsomal fraction of the homogenate.     

Terpenoid metabolites from the aerial part of Artemisia lagocephala

Six naturally occurring terpenoids were isolated from the hexane extract of rabbit-head wormwood Artemisia lagocephala (Fisch. ex Besser) DC. The terpenoids’ structures were elucidated by spectroscopic and chemical methods as 3β-acetoxycycloartan-24-ozonide (1), 3β-acetoxycycloartan-24-al (2), 25,26,27-trisnor-3β-acetoxycycloartan-24-ol (3), 24,25,26,27-tetranor-3β-acetoxycycloartan-23-ol (4), and the previously known caryophyllene oxide (5) and (1R,4S)-p-menth-2-en-1-ol (6).     

Sterols with unusual nuclear unsaturation from three cultured marine dinoflagellates

Several new 4α-methyl sterols with unusual unsaturation in the Δ⁸⁽¹⁴⁾-or Δ¹⁴-positions, 4α,24S-dimethyl-5α-cholest-8 (14)-en-3β-ol, 4α-methyl-24ξ-ethyl-5α-cholest-8(14)-en-3β-ol, 4α-methyl-24(Z)-ethylidene-5α-cholest-8(14)- en-3β-ol, 4α,23 (or 22),24ξ-trimethyl-5α-cholesta-8(14),22-dien-3β-ol, 4α,24S(or 23ξ)-dimethyl-5α-cholest-14-en-3β-ol and 14-dehydrodinosterol, have been isolated from extracts of the cultured marine dinoflagellates Amphidinium carterae, A. corpulentum and Glenodinium sp. 4α-Methyl-24ξ-ethyl-5α-cholestan-3β-ol was isolated from the steryl ester fraction of Glenodinium sp. The structures of these new sterols are based upon extensive 360 MHz ¹H NMR and MS analyses.     

A new C26sterol peroxide from the opisthobranch mollusk Adalaria sp. and the sea pen Virgularia sp.

5,8α-Epidioxy-(22E)-24-nor-5α-cholesta-6,22-dien-3β-ol (8) has been isolated from the sea pen Virgularia sp. and has been observed as a component of a mixture isolated from the opisthobranch mollusk Adalaria sp. The structure of 8 was deduced from spectroscopic data. A further six sterol peroxides isolated from Adalaria and six from Virgularia were tentatively identified on the basis of spectroscopic analysis of mixtures.     

Sterols of the siphonous marine alga Codium fragile

The marine siphonous green alga, Codium fragile, was shown to contain two 25-methylene sterols. These were identified as (24S)-24-ethylcholesta-5.25-dien-3β-ol and the previously unknown (24S)-24-methylcholesta-5,25-dien-3β-ol for which the trivial name codisterol is proposed.