Sterols in marine invertebrates

Recent progress on the analytical techniques of steroids by gas chromatography (GC) and high-performance liquid chromatography (HPLC) and their combination with mass spectrometry (MS) has opened a new field for studies on natural sterols. Thus, during the past decade, a great deal of information has become available on the structure and biosynthesis of sterols in invertebrates. 

Sterols of marine invertebrates have been found to comprise most complex mixtures more than 120 sterols have been isolated and their structures determined [1]. Analysis of these sterols has been performed largely by GC, GC/MS and HPLC. Stereochemical details were determined by NMR or by synthetic work. Fig. 1 demonstrates the effectivity of a capillary colunrn a and b showing the GC analysis of a sterol fraction obtained from the sponge, Hymeniacidon perleve using a packed and a capillary column, respectively [2]. 

Sterol patterns in marine invertebrates reflect the complexity of mixtures of sterols arising through food chains. Even in the same species, the sterol fractions show different patterns depending upon the location where the organisms have been collected. The capability of further biochemical modification of the dietary sterols makes the sterol mixtures even more complex. The symbiotic relationship between organisms also complicates the sterol compositions. These conditions are quite different from those affecting sterols of terrestrial organisms. Many sterols of unprecedented structures have now been isolated from marine sources. 

Several excellent comprehensive reviews [1-11] on the structures and biosynthesis of marine sterols are available. This chapter focuses mainly on recent advances. Sterols widely distributed in marine invertebrates are shown in Fig. 2, which shows 

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Side chain modification of sterols in marine invertebrates... 

Biosynthesis of branched and highly alkylated sterols in marine invertebrates has been the subject of speculation. Tris- or quadruple-methylation would produce branched sterols in Porifera. Epi-codisterol (C-24-Epi-9B) can be assumed to be a precursor of 25(26)-dehydroaplysterol (20) which is biomethylated again to give... 

Isolation, biosynthesis, and metabolism of sterols in marine invertebrates constitutes an active field of reseach (21-26) the discovery of... 

Bohlin, L., H.P. Gehrken, P.J. Scheuer, and C. Djerassi Minor and Trace Sterols in Marine Invertebrates XVI. 3 -Hydroxymethyl-A- or-5a-gorgostane, a Novel Sponge Sterol. Steroids 35, 295 (1980). 

Li, L.N., U. Sjostrand, and C. Djerassi Minor and Trace Sterols in Marine Invertebrates. 19. Isolation, Structure Elucidation, and Partial Synthesis of 24-Methylene-25-ethylcholesterol (Mutasterol) First Example of Sterol Side-Chain Bioalkylation at Position 25. J. Am. Chem. Soc. 103,115 (1981). 

Bohlin, L., U. Sjostrand, C. Djerassi, and B.W. Sullivan Minor and Trace Sterols in Marine Invertebrates. Part 20. 3 -Hydroxymethyl-A-/iur-patinosterol and 3 -Hydroxymethyl-A-nur-dinosterol. Two New Sterols with Modified Nucleus and Side-chain from the Sponge Teichaxinella morchella. J. Chem. Soc., Perkin Trans. I 1981,1023. 

Kho, E., D.K. Imagawa, M. Rohmer, Y. Kashman, and C. Djerassi Sterols in Marine Invertebrates. 22. Isolation and Structure Elucidation of Conicasterol and Theonellasterol, Two New 4-Methylene Sterols from the Red Sea Sponges Theonella conica and Theonella swinhoei. J. Org. Chem. 46,1836 (1981). 

Zielinski, J., T. Milkova, S. Popov, N. Marekov, and C. Djerassi Minor and Trace Sterols in Marine Invertebrates. 34. Isolation and Structure Elucidation of 24-Methyl-5a-cholesta-7,9(ll),24(28)-trien-3P-ol, the First Naturally Occurring... 

Eggersdorfer, M.L., W.C.M.C. Kokke, C.W. Crandell, J.E. Hochlowski, and C. Djerassi Sterols in Marine Invertebrates. 32. Isolation of 3P-(Hydroxymethyl)-A-nur-5a-cholest-15-ene, the First Naturally Occurring Sterol with a 15-16 Double Bond. J. Org. Chem. 47, 5304 (1982). 

Itoh, T., D. Sica, and C. Djerassi Minor and Trace Sterols in Marine Invertebrates. 36. (245)-24/f-Isocalysterol A New Steroidal Cyclopropene from the Marine Sponge Calyx niceaensis. J. Org. Chem. 48, 890 (1983). 

Bohlin, L, Sjostrand, U., Djerassi, C., and Sullivan, C. (1981) Minor and trace sterols in marine invertebrates. 20. Two new sterols with modified nucleus and side[Pg.1003]

Kho, E., Imagawa, D.K.. Rohmer, M., Kashman, Y., and Djerassi, C. (1981) Sterols in marine invertebrates. 22. Isolation and structure elucidation of conicasterol and theonellasterol, two new 4-methylene sterols from the Red Sea sponges Theonella conica and Theondla sivinhoei.J. Org. Chem., 46,1836-1839. 

Zielinski, J., Milkova, T, Popov, 1., Marekov, N., and Djerassi, C. (1982) Minor and trace sterols in marine invertebrates. 34. Isolation and structure eluddation of 24-methyl-5a-cholesta-7,9(ll),24(28)-trien-3p-ol, the first naturally occurring unsaturated marine sterol. 

Bohlin, L., Sjostrand, U., Sodano, G., and Djerassi, C. (1982) Sterols in marine invertebrates. 33. Structure of five new 3p-(hydroxymefhyl)-A-uor-steranes indirect evidence for transformation of dietary precursors in sponges. J. Org. Chem., 47, 5309-5314. 

Carlson, R.M.K., Popov, S., Massey, I., Delselh, C., Ayanoglu, E., Varkony, T.H., and Djerassi, C. (1978) Minor and trace sterols in marine invertebrates VI. Occurrence and possible origins of sterols possessing unusually short hydrocarbon side chains. Bioorg. Chem., 7,453- 79. 

Delseth, C., Toleda, L., Scheuer, P.J., Wells, R.J., and Djerassi, C. (1979) Minor and trace sterols in marine invertebrates. XL Two new sterols from the Pacific sponges Terpios zeteki and Dysidea herbacea. Helv. Chim. Acta, 62,101-109. 

Gebreyesus, T., Stoilov, I., Luo, F.-T., and Djerassi, C. (1985) Minor and trace sterols in marine invertebrates 55. The isolation, structure elucidation and synthesis of ergosta-5,24(28),25-trien-3 3-ol. Steroids, 45, 447-452. 

Li, N.L. and Djerassi, C. (1981b) Minor and trace sterols in marine invertebrates. 30. Isolation, structure elucidation and partial synthesis of 26-methylstrongylosterol and 28-methylxestosterol two marine sterols arising by a novel quadruple biomethylation sequence. Tetrahedron Lett., 22,4639-4642. 

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