Marine sterols

Field: Chemistry (Physical Sciences)

A chemotaxonomic investigation of the family Zoanthidae, phylum Coelenterata, with sterols as the chemical parameter showed that most of the species contained a mixture of from four to six individual sterols. Each sterol mixture was characteristic of a given zoanthid, as shown by reproducible gas chromatographic patterns. Fingerprint gas chromatograms are therefore a valid tool to aid in the classification of zoanthids. Previous work had established the presence of 24-methylenecholesterol in Zoanthus proteus and palysterol in Palythoa mammilosa. Reinvestigation of "palysterol" from Palythoa sp. proved it to be a mixture of at least five compounds which could be separated by preparative gas chromatography. The major component (ca. 60% of the palysterol mixture) was shown to be identical with 22,23-dihydrobra.ssicasterol, a sterol which had not been previously isolated from marine or other natural sources. A second sterol (ca. 20% of palysterol) was shown to be identical with gorgosterol. Structural investigation of gorgosterol has not led to complete structural elucidation. The remaining three sterols of the palysterol mixture were shown to be identical with cholesterol (10-15%), brassicasterol (1-2%), and 24ξ-ethylcholesterol (1-2%). "Zoansterol", a sterol mixture isolated from Zoanthus confertus, was shown to be composed of four sterols. Three sterols were shown to be identical with cholesterol, brassicasterol, and 24ξ-methylcholesterol. The fourth component, 24-methylenecholesterol, was indicated by gas chromatographic behavior. A sterol isolated from a toxic Palythoa sp. consisted of essentially a single compound which proved to be 24-methylenecholesterol. The sterols of members of five classes of the phylum Echinodermata were studied. The results indicate a close relationship of sea stars and sea cucumbers on the one hand, and of brittle stars, sea urchins, and sea lilies on the other. Five sterols isolated from the sterol mixture of the sea star Acanthaster planci were shown to be Δ^7-cholestenol, 24ξ-methyl-Δ^7-cholestenol, 24ξ-ethyl-Δ^7-cholestenol, 24ξ-methyl-Δ^7,22- cholestadienol, and the Δ^7- analogue of gorgosterol. Mass spectra and gas chromatograms of the sterols were used to distinguish Δ^7- from Δ^5-sterols. The sterols of the sea cucumber Holothuria atra proved to be closely analogous to those found in the sea star. Cholesterol was shown to be the major sterol in the sterol mixture of the sea urchin, Echinothrix diadema. It was associated with minor quantities of 24ξ-ethyl- and 24ξ-methylcholesterol. From the sterol mixture of the brittle star Ophiocoma insularia five sterols were isolated. The major sterol was identical with cholesterol. The second most abundant component was identified as 24-ethylidinecholesterol (fucosterol?) with small inseparable impurities of 24ξ-ethylcholesterol. Brassicasterol, 24ξ-methylcholesterol, and stigmasterol were identified as the minor components. Gas chromatographic and mass spectrographic evidence indicated the presence of 22-dehydrocholesterol, chole sterol, brassicasterol, 24ξ-methylcholesterol, stigmasterol, and 24ξ-ethylcholesterol in the sterol mixture of a crinoid Antedon sp. The sterol mixture of a sponge, Halichondria magnicanulosa, was shown to consist predominantly of cholesterol and minor quantities of brassicasterol and 24ξ-methylcholesterol.