W.C.M.C. Kokke

Sterols with unusual nuclear unsaturation from three cultured marine dinoflagellates

Abstract Several new 4α-methyl sterols with unusual unsaturation in the Δ 8(14) -or Δ 14 -positions, 4α,24 S -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,24 S (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 1 H NMR and MS analyses.

Biosynthetic studies of marine lipids—3 : Experimental demonstration of the course of side chain extension in marine sterols

Abstract The Pacific sponge Aplysina fistularis was fed cholesterol-[4- 14 C],(24 R )-methyl-25-dehydrocholesterol-[26- 14 C] (epicodisterol[26- 14 C]), (24 S )-methyl-25-dehydrocholesterol-[26- 14 C] (codisterol-[26- 14 C]), and 24-methylenecholesterol-[28- 14 C]. Only epicodisterol, which has the same stereochemistry at C-24 as (24 R ,25 S )-24,26-dimethylcholesterol (aplysterol), was converted with high efficiency into (24 R )-24,27-dimethyl-25-dehydrocholesterol (25-dehydroaplysterol). Further side chain extension [to E -(24 R )-24,26,27-trimethyl-25-dehydrocholesterol (verongulasterol)] could also be demonstrated.

Isolation of two new c30 sterols, (24e)-24-n-propylidenecholesterol and 24ξ-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.

Isolation of sterols with cyclopropyl-containing side chains from the cultured marine alga peridinium foliaceum

Abstract The sterol fraction of the cultured dinoflagellate Peridinium foliaceum contains in addition to cholesterol, 24-methylcholesterol, 4,24-dimethylcholesterol and dinosterol ( 3c ) small amounts of the cyclopropyl-containing sterols gorgosterol ( 1a ) and 5α-gorgostanol ( 1b ) as well as 4α-methylgorgostanol ( 1c ) and E-4α,22ξ,23ξ (or 24ξ)-trimethylcholest-17(20)-en-3β-ol ( 6c or 7c ). The biosynthetic implications of the first isolation of such sterols from a free-living alga are emphasized.

Sterols of the cultured dinoflagellate Pyrocystis lunula

Eighteen components of the sterol fraction of Pyrocystis lunula have been identified. In addition to 4 alpha-methyl sterols (typical dinoflagellate sterols), regular sterols, both with a saturated and delta 5-unsaturated skeleton, were isolated, together with delta 4-3-keto steroids including the hitherto unknown 23,24R-dimethyl-4,22E-cholestadien-3-one.

Minor sterols of marine invertebrates 37.★ Isolation of novel coprostanols and 4α-methyl sterols from the tunicate Ascidia nigra

Abstract The complex sterol mixture isolated from A, nigra was found to contain a low level of Δ 4 -3-keto steroids, 5β-stanols and 4α-methyl sterols in addition to regular (4-demethyl) sterols. The following new marine sterols were isolated and identified using MS and 360 MHz NMR: 5β-cholest-22E-en-3β-ol, 24S-methyl-5β-cholest-22E-en-3β-ol, 24-methylene-5β-cholestan-3β-ol, both epimers at C-24 of 4α-methyl-24-ethyl-5α-cholest-22E-en-3β-ol, 4α, 22ξ, 23ξ-(or 24ξ-)trimethyl-5α-cholest-8(14)-en-3β-ol and (22S, 23S, 24S)-4α-24-dimethyl-22, 23-methylene-5α-cholestan-3β-ol. The latter sterol and 23-demethylgorqosterol have opposite configurations at C-22, C-23, and C-24; the Δ 8 (14) sterol has an unprecedented side chain.

Sterol synthesis by cultured zooxanthellae; implications concerning sterol metabolism in the host-symbiont association in caribbean gorgonians

Abstract 1. 1. The sterol composition of three taxonomically diverse Caribbean gorgonians, Briareum asbestinum (Pallas), Muriceopsis flavida (Deichmann and Bayer), and Gorgonia mariae (Bayer) is reported. As noted earlier, gorgosterol and 23-demethylgorgosterol are major components. 2. 2. The sterol composition of cultured, single colony-derived zooxanthellae isolated from these gorgonians reflects a preponderant synthesis of 4α-methyl sterols, with gorgosterol and 23-demethylgorgosterol being absent. 3. 3. Sterol analyses of three zooxanthellae-free Pacific gorgonians, Pacifigorgia adamsii (Verrill), Lophogorgia alba (Duchaissang and Michelotti) and Lophogorgia cuspidata (Verrill) point towards the existence of dietary-sterols, thus demonstrating a contrast with the composition of zooxanthellae-bearing Caribbean gorgonians. 4. 4. Our results lead to the conclusion that either some unprecedented steps in sterol biosynthesis are occurring or that sterol synthesis by zooxanthellae proceeds in different directions depending whether the algae live symbiotically or alone.

4α-methyl-24S-ethyl-5α-cholestan-3β-ol and 4α-methyl-24S-ethyl-5α-cholest-8(14)-en-3β-ol, two new sterols from a cultured marine di

Abstract Twenty sterols of the cultured zooxanthellae (dinoflagellate symbionts) originally derived from the Caribbean gorgonian coral Briareum asbestinum w

Isolation and synthesis of 23-methyl-22-dehydrocholesterol -a marine sterol of biosynthetic significance

Anew sterol, 23-methyl-22-dehydrocholesterol, and several closely relatedsterols, have been isolated from cultures of the dinoflagellat symbiont (zooxanthella) from the marine zoanthid Zoanthus sociatus. The structural features of these sterols suggest that direct bioalkylation of a Δ22 double bond may be a new biosynthetic route to novel sterol side chains.

Peridinosterol - a new Δ17-unsaturated sterol from two cultured marine algae

Abstract X-ray diffraction analysis of peridinosterol p-bromobenzoate has shown the parent sterol to be E-4α,23R,24R-trimethylcholest-17(20)-en-3β-ol - a new member of the rare Δ 17 -unsaturated sterol class. Its possible biosynthetic origin is discussed.