Minor and trace sterols in marine invertebrates. 1. General methods of analysis

Tapping the archives: the sterol composition of marine sponge species, as determined non-invasively from museum-preserved specimens, reveals biogeographical features

Over 8600 species are currently recorded in the phylum Porifera (sponges). They produce a large diversity of biochemical compounds including sterols, with more than 250 different sterols identified. Some of these sterols are of great interest, due to their use for fingerprinting in ecological and biomarker (molecular fossil) studies. As a large number of identified extant species from biodiversity surveys are housed in museum collections, preserved in ethanol, these present a potentially rich source of identified specimens for comparative lipid analyses. Here, we show that, in at least one species, sterol distributions obtained from the ethanol used to preserve specimens of sponges were representative, and comparable to the sterol distribution obtained from wet-frozen and from freeze-dried tissue from the same species. We employed both GC-MS and two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS), with an improved signal-to-noise ratio for even minor constituents. Analysis of two additional specimens of the same species, but of different provenance, resulted in detection of marked differences in sterol composition, which could be attributed to variations in geography, environmental conditions, microbial communities, diet or cryptic speciation. The possibility of using ethanol from identified, preserved museum sponges could drastically increase the number of available samples. This could enable the study of their sterol complements, and the detailed investigation of differences due to geographical and oceanographic, phylogenetic, and other factors in unprecedented detail.

Sterol patterns of cultured zooxanthellae isolated from marine invertebrates: Synthesis of gorgosterol and 23-desmethylgorgosterol by aposymbiotic algae

QUANTITATIVE STEROL COMPOSITIONS OF CULTURED ZOOXANTHELLAE ISOLATED FROM VARIOUS PACIFIC AND ATLANTIC INVERTEBRATE HOSTS: Zoanthus sociatus (a zoanthid), Oculina diffusa (a scleractian coral), Tridacna gigas (a giant clam), Melibe pilosa (a nudibranch), and Aiptasia pulchella (a sea anemone) are reported. The results clearly demonstrate large differences in sterol patterns of zooxanthellae and that there is no obvious relationship between the taxonomic affiliation of the host and the sterol pattern of its isolated symbiont. The sterols of the zooxanthellae of O. diffusa (Cnidaria) and T. gigas (Mollusca) are qualitatively equivalent. Based on the structures of the two major free sterols synthesized by each alga, the zooxanthellae from different hosts were separated into three distinct groups. It was also found that an aposymbiotic alga can synthesize the unique marine sterols gorgosterol and 23-desmethylgorgosterol. Most of the sterols were identified by using mass spectroscopy and 360-MHz proton magnetic resonance. Spectroscopic data are reported for four novel sterols-(23,24R)-dimethyl-5alpha-cholest-(22E)-en-3beta-o l, 23-methyl-5alpha-cholest-22E-en-3beta-ol, cholesta-5,14-dien-3beta-ol, and 4alpha-methyl-5alpha-cholesta-8(14)-24-dien-3beta-ol.

Effect of cobalt ions on the metabolism of some volatile and polar compounds in the marine invertebrates Mytilus galloprovincialis and Actinia equina

The compositions of the volatile and polar fractions from two coexisting Black Sea invertebrates, the mussel Mytilus galloprovincialis and the beadlet anemone Actinia equina, were established. The main metabolites in the volatile fraction from the investigated animals appeared to be methyl esters of fatty acids and fatty aldehydes. In the polar fraction from both animals low concentrations of free acids and nitrogen-containing compounds were obtained. Free carbohydrates were in much higher concentrations in M. galloprovincialis than in A. equina. Some sterols, probably as polar conjugates, were identified mainly in A. equina. Significant changes among all compounds appeared after treatment of both invertebrates with two different concentrations of cobalt ions. The variety of changes in each invertebrate could be due to their different evolutionary status. The effect of cobalt ions was often stronger at medium cobalt-ion concentrations.

Minor and trace sterols in marine invertebrates. 62. Novel coprostanols with unusual side chains from the marine sponge Calyx nicaeensis

Seventeen stanols with a variety of unusual side chains and possessing the rare 5 beta-dihydro nucleus have been isolated from the sponge Calyx nicaeensis. These stanols probably result from bacterial metabolism of the endogenous sponge sterols.

Minor and trace sterols from marine invertebrates 56. Novel coprostanols from the marine sponge Petrosia ficiformis

Twelve stanols possessing the rare 5 beta-dihydro nucleus have been isolated from the marine sponge Petrosia ficiformis. These stanols have not previously been encountered in any samples of P. ficiformis which we have examined and appear to be the result of bacterial metabolism of the endogenous sponge sterols.

Marine 4-methyl sterols: synthesis of C-24 epimers of 4 alpha, 24-dimethyl-5 alpha-cholestan-3 beta-ol and 360 MHz 1HNMR comparisons to the natural product from Plexaura homomalla

Comparison of the highfield 1HNMR spectrum of 4 alpha, 24-dimethyl-5 alpha-cholestan-3 beta-o1 isolated by open column adsorptive chromatography and reversed-phase HPLC from P. homomalla with those of the corresponding synthetic 24 alpha and 24 beta compounds demonstrate that the gorgonian natural product is purely 24 beta, the same C-24 configuration found in sterols related to dinosterol and gorgosterol. 360 MHz 1HNMR data are also reported for synthetic 4 alpha, 24 beta-dimethyl-5 alpha-cholest-22E-en-3 beta-o1 (another P. homomalla natural product). The use of 1HNMR correlations in assigning C-24 configurations of 24-methyl marine sterols possessing various nuclei is examined and discussed. Analyses of the methyl sterol components of P. homomalla are tabulated and discussed with regard to origin and plausible biosynthetic interrelationships in light of the C-24 configurational findings.

Occurrence and seasonal variation of 19-norcholest-4-en-3-one and 3 beta-monohydroxy sterols in the Californian gorgonian, Muricea californica

The first natural occurrence of 19-norcholestenone is reported, together with 17 sterols and one other delta 4-3-ketone in the extracts of the Californian gorgonian, Muricea californica (Aurivillius). Six additional demethyl sterols and five additional 4-monomethyl sterols which remain unidentified were also detected. Lipid extracts of M. californica from a winter and summer collection were split by various chromatographic methods into free sterol, steryl ester, and steryl conjugate fractions. Sterol compositions (determined by CG and CG-MS) of each fraction, subsequent to hydrolysis, are tabulated and discussed with respect to plausible origins of observed variations. The possible relationship of the Muricea 19-nor-steroidal ketone to other naturally occurring 19-nor-steroids is discussed.

Minor and trace sterols in marine invertebrates XVII. (24R)-24,26-Dimethylcholesta-5,26-dien-3 beta-OL, a new sterol from the sponge Petrosia ficiformis

More than thirty monohydroxy sterols were detected in the marine sponge Petrosia ficiformis, ranging from the ubiquitous 24-norcholesta-5,22-dien-3 beta-ol to the C30 sterol, 24-propylidenecholesterol. A new minor sterol was isolated and shown by spectral analysis and comparison with a synthetic sample to be (24R)-24,26-dimethylcholesta-5,26-dien-3 beta-ol [26(29)-dehydroaplysterol] (12).

Isolation of two new C30 sterols, (24E)-24-N-propylidenecholesterol and 24 epsilon-N-propylcholesterol, from a cultured marine Chrysophyte

Two new sterols, (24E)-24-n-propylidenecholesterol and 24 epsilon-n-propylcholesterol, were isolated from a cultured marine Chrysophyte. Since most of the steroids found in marine invertebrates are unchanged or modified sterols of algal or symbiotic origin, the discovery of these two unusual sterols in a unicellular alga grown under well-defined conditions contributes to our knowledge of sterols in marine food chains and offers a potential substrate for biosynthetic labeling experiments.

The diversity of marine sterols and the role of algal bio-masses; from facts to hypothesis

Modern analytical methods have revealed the great variety of marine sterols, which possess many different side chains and unsaturation patterns. Such biochemical transformations require well-defined mechanistic pathways, and there must be some 'Raison d'Etre' for a situation which has withstood evolution and adaptive changes. However, in this area, insufficient and sometimes not very substantial experimental work has made it difficult to see correlations, and hence to form a solid hypothesis. A review is now presented in which the molecules dissolved in sea water, or found in marine organisms are considered with particular reference to algal production, and to the bio-ecological significance of the main sterols.

High-pressure liquid chromatography of steroids

After a brief discussion of the merits and limitations of high-pressure liquid chromatography (HPLC) relative to other chromatographic methods, special problems in the application to steroids are discussed. Publications on HPLC of steroids are then discussed under the headings of individual classes, arranged generally in the order of increasing polarity.

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.

Minor and trace sterols in marine invertebrates V. Isolation, structure elucidation and synthesis of 3beta-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-3beta-ol, cholesterol, 5alpha-cholestan-3beta-ol, 24epsilon-methylcholesta-5,22-dien-3beta-ol, 24epsilon--methylcholesterol, 24epsilon-ethylcholesta-5,22-dien-3beta-ol and 24,28-dehydroaplysterol, a new minor sterol was isolated and shown by spectral analysis as well as partial synthesis to be 3beta-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 3beta-hydroxypregn-5-en-20-one and 3beta-hydroxy-5alpha-pregnan-20-one.