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Desmosterol
Names
IUPAC name
3S,8S,9S,10R,13R,14S,17R)-10,13-dimethyl-17-[(2R)-6-methylhept-5-en-2-yl]-2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-3-ol
Other names
Desmosterol

24-Dehydrocholesterol

Cholesta-5,24-dien-3β-ol
Identifiers
Properties
C27H44O
Molar mass 384.6
Appearance Solid
Melting point 121.5°C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Desmosterol (Cholesta-5,24-dien-3β-ol) is a lipid present in the membrane of phytoplankton. These are autotrophic organisms which undergo photosynthesis and rely on sunlight for energy, living in shallower waters. Structurally, desmosterol has a similar backbone to cholesterol, with the exception of an additional double bond in the structure of desmosterol. Biologically, the similarity can be seen through the synthesis of cholesterol in the human body, as desmosterol is the immediate precursor to cholesterol.[1]

Structure of cholesterol and its immediate precursor, desmosterol.

Background

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Desmosterol is classified as a cholestadienol, a subgroup of a wider known group of sterols, which are organic compounds naturally occurring in eukaryotes. The presence of desmosterol in oceans and lakes has potential to diagnose anoxic conditions and for studying trends in steroid chemistry during the early stages of diagenesis.[2] Desmosterol has been found in samples of Rhizosolenia setigera Brightwell in Western Svalbard[3] and from surface sediment off the Peruvian Shelf sediment-water interface.[2]

Desmosterol was first described and isolated in 1955 from chick embryo sterol with a 2% yield and postulated as being a biological precursor to cholesterol by Stokes et al.[4] The first known isolation of desmosterol in invertebrates was published in 1957 by Fagerlund and Idler.[5] This new sterol was isolated in large amounts from balanus glandula, a barnacle species found on the North American Pacific coast. Additionally, small amounts of desmosterol have been found in other crustaceans such as lobster and shrimp in the homarus americanus and pandalus borealis species. This strengthens the conclusion that desmosterol must be created exogenously as crustaceans have not been seen to biosynthesise sterols. [6]

Biological Occurence

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Desmosterol has been largely found within a large population of marine invertebrates. Major sources include: barnacles[5], red algae[7], annelida[8], thalassiosirales[9], and molluscs[10]. This has led to the idea of an exogenous origin of desmosterol in phytoplankton. Desmsterol was identified in red algae: Laurencia pinnatifida, Polusiphonia nigrescens, Porphyra purpurea, and dulse (Rhodymenia palmata), in 1967, after no previous identification.

In the 1968 paper by Idler, Saito and Wiseman,[7] dulse samples were analysed and the sterols present were determined by gas liquid chromatography. Samples were collected near Grand Manan Island, New York in 1964 and 1965 gave a significant difference in presence of desmosterol, with the latter collected sample with over 70% desmosterol. The samples collected in June and July of 1967 showed a smaller difference, of 30%.[7]

Sterol composition of dulse samples from Grand Manav Island, New York, with data taken from Idler's 1968 paper.[7]

Biosynthesis

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There are two major pathways for cholesterol biosynthesis, being the Kandutsch-Russell and Bloch pathways.[11] The Bloch pathway, named after Konrad Bloch, occurs naturally alongside the mevalonate pathway in humans within the cell. The discovery of this pathway led to Bloch, joint with Feodor Lynen, to receive a Nobel Prize in Physiology or Medicine in 1964. The award was awarded “for their discoveries concerning the mechanism and regulation of the cholesterol and fatty acid metabolism”.[12]

Synthetic pathway from desmosterol to cholesterol

Preservation

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Desmosterol has been seen to be present in marine sponges as a biomarker. However, bacterial symbiont Sterol 24-C-methyltransferases is capable of the alkylation of desmosterol to other sponge biomarkers, 24-isopropenylcholesterol, and 24-isopropylidenecholesterol.[13] It should be noted there is insignificant data which shows that desmosterol has good preservation potential.

Use as a Biomarker

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Desmosterol is important through its use as a biomarker for the Chaetoceros calcitrans[14] and R. setigera and N. closterium[15] diatoms as well as Rhodophyceae[16]. However, desmosterol has potential to be used as a taxonomic marker for diatoms where it exists as the dominant sterol, such as Rhizosolenia. [15]

Peruvian Shelf

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Diatoms and Silicoflagellates are classes of phytoplankton present in sedimentary material from the sediment water interface in the Peruvian Shelf region.[17] Mineralogical analysis of these suggested large volumes of phytoplankton. Researchers at the University of Bristol examined the sterol composition of these sedimentary rocks which have gone through oxygen depletion, leading to anoxic conditions. These conditions have enhanced preservation of lipids present during the time of formation, around 1 year prior, and limited degradation of these compounds.

Measurement techniques

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Desmosterol has seen to be identified most commonly through chemical constants, ozonolysis, infrared, NMR, and mass spectrometry techniques.[18] The use of thin-layer and gas-liquid chromatography to measure desmosterol is less common from the development of more advanced techniques.

GC-MS

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Samples from water sources are first extracted and partially purified before analysis. Sterols are commonly first derivatised after purification. Lipid extracts can be separated into their fragments by ionisation using Gas Chromatography followed by Mass Spectroscopy analysis. Desmosterol has a characteristic m/z peak at 384, seen in the mass spectra.[3]

Ozonolysis

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Desmosterol has been identified through ozonolysis of the sample, with the ozonolysis product of desmosterol having a melting point of 128°C, and an Rf value of 0.31 with paper-chromatography with n-hexane and N,N-dimethyl formamide. The ozonolysis product also has ratios C: 45.68; H: 4.45; N: 23.21.[18]

References

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  1. ^ Bloch, Konrad (1965-10). "The Biological Synthesis of Cholesterol". Science. 150 (3692): 19–28. doi:10.1126/science.150.3692.19. ISSN 0036-8075. {{cite journal}}: Check date values in: |date= (help)
  2. ^ a b Smith, D.J.; Eglinton, G.; Morris, R.J.; Poutanen, E.L. (1983). "Aspects of the steroid geochemistry of an interfacial sediment from the Peruvian upwelling". Oceanologica Acta. 6 (2): 211–219. {{cite journal}}: line feed character in |title= at position 63 (help)
  3. ^ a b Belt, Simon T.; Brown, Thomas A.; Smik, Lukas; Tatarek, Agnieszka; Wiktor, Józef; Stowasser, Gabriele; Assmy, Philipp; Allen, Claire S.; Husum, Katrine (2017-08-01). "Identification of C25 highly branched isoprenoid (HBI) alkenes in diatoms of the genus Rhizosolenia in polar and sub-polar marine phytoplankton". Organic Geochemistry. 110: 65–72. doi:10.1016/j.orggeochem.2017.05.007. ISSN 0146-6380.
  4. ^ Stokes, W. M.; Fish, W. A.; Hickey, F. C. (1956-05). "Metabolism of cholesterol in the chick embryo. II. Isolation and chemical nature of two companion sterols". The Journal of Biological Chemistry. 220 (1): 415–430. ISSN 0021-9258. PMID 13319360. {{cite journal}}: Check date values in: |date= (help)
  5. ^ a b Fagerlund, U. H. M.; Idler, D. R. (1957-12). "Marine Sterols. IV. 24-Dehydrocholesterol: Isolation from a Barnacle and Synthesis by the Wittig Reaction". Journal of the American Chemical Society. 79 (24): 6473–6475. doi:10.1021/ja01581a030. ISSN 0002-7863. {{cite journal}}: Check date values in: |date= (help)
  6. ^ Gagosian, Robert (1974). Summary of Investigations Conducted in 1974. Massachusetts: Woods Hole Oceanographic Institution. pp. C-16.
  7. ^ a b c d Afaq-Husain, S.; Shameel, M.; Usmanghani, K.; Ahmad, M.; Ahmad, V. U. (2021-01-07), "Phycochemical Studies on Dermonema abbottiae (Nemaliales — Rhodophyta)", Phycochemical Studies on Dermonema abbottiae (Nemaliales — Rhodophyta), De Gruyter, pp. 215–220, doi:10.1515/9783112328101-024, ISBN 978-3-11-232810-1, retrieved 2023-05-21
  8. ^ Kobayashi, Masaru; Nishizawa, Motohito; Todo, Kagemi; Mitsuhashi, Hiroshi (1973). "Marine Sterols. I. Sterols of Annelida, Pseudopotamilla occelata MOORE". Chemical & Pharmaceutical Bulletin. 21 (2): 323–328. doi:10.1248/cpb.21.323.
  9. ^ Limnology and Oceanography. 55 (1). 2010-01. doi:10.1002/lno.v55.1. ISSN 0024-3590 http://dx.doi.org/10.1002/lno.v55.1. {{cite journal}}: Check date values in: |date= (help); Missing or empty |title= (help)
  10. ^ Idler, D.R.; Wiseman, P. (1971-10). "Sterols of molluscs". International Journal of Biochemistry. 2 (11): 516–528. doi:10.1016/0020-711X(71)90021-8. {{cite journal}}: Check date values in: |date= (help)
  11. ^ Singh, Pushpendra; Saxena, Roopali; Srinivas, Gunda; Pande, Gopal; Chattopadhyay, Amitabha (2013-03-15). Koval, Michael (ed.). "Cholesterol Biosynthesis and Homeostasis in Regulation of the Cell Cycle". PLoS ONE. 8 (3): e58833. doi:10.1371/journal.pone.0058833. ISSN 1932-6203.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  12. ^ "The Nobel Prize in Physiology or Medicine 1964". NobelPrize.org. Retrieved 2023-05-21.
  13. ^ Brown, Malory O.; Olagunju, Babatunde O.; Giner, José-Luis; Welander, Paula V. (2022-05-16). "Bacterial sterol methylation confounds eukaryotic biomarker interpretations". doi:10.1101/2022.05.16.491679. {{cite journal}}: Cite journal requires |journal= (help)
  14. ^ "Comp. biochem. physiol". Comparative Biochemistry and Physiology. 9 (2): 160. 1963-06. doi:10.1016/0010-406x(63)90020-3. ISSN 0010-406X. {{cite journal}}: Check date values in: |date= (help)
  15. ^ a b Barrett, Stephanie M.; Volkman, John K.; Dunstan, Graeme A.; LeRoi, Jeannie-Marie (1995-06). "STEROLS OF 14 SPECIES OF MARINE DIATOMS (BACILLARIOPHYTA)1". Journal of Phycology. 31 (3): 360–369. doi:10.1111/j.0022-3646.1995.00360.x. ISSN 0022-3646. {{cite journal}}: Check date values in: |date= (help)
  16. ^ "Handbook of Psychopharmacology. Edited by L. L. Iversen, S. D. Iversen and S. H. Snyder. Plenum Press: New York. 1978. - Volume 7Principles of Behavioral Pharmacology. (Pp. 453; illustrated; $34.50.) Plenum Press: New York. 1978. - Volume 8Drugs, Neurotransmitters, and Behavior. (Pp. 590; illustrated; $39.50.) Plenum Press: New York. 1978. - Volume 9Chemical Pathways in the Brain. (Pp. 410; illustrated; $29.50.) Plenum Press: New York. 1978. - Volume 10Neuroleptics and Schizophrenia. (Pp. 250; illustrated; $25.00.) Plenum Press: New York. 1978. - Volume 11Stimulants. (Pp. 476; illustrated; $32.50.) Plenum Press: New York. 1978. - Volume 12Drugs of Abuse. (Pp. 420; illustrated; $32.50.) Plenum Press: New York. 1978. - Volume 13Biology of Mood and Anti-anxiety Drugs. (Pp. 440; illustrated; $32.50.) Plenum Press: New York. 1978. - Volume 14Affective Disorders: Drug Actions in Animals and Man. (Pp. 379; illustrated; $29.50.) Plenum Press: New York. 1978". Psychological Medicine. 9 (1): 194–195. 1979-02. doi:10.1017/s0033291700021735. ISSN 0033-2917. {{cite journal}}: Check date values in: |date= (help)
  17. ^ Evmiridis, N.P.; Karayannis, M.I. (1983). "A mechanistic investigation of the reaction of L-leucine with trinitrobenzenesulfonic acid". Analytica Chimica Acta. 151: 211–219. doi:10.1016/s0003-2670(00)80078-1. ISSN 0003-2670.
  18. ^ a b Idler, D; Saito, A; Wiseman, P (1968-04). "Sterols in red algae (Rhodophyceae)1". Steroids. 11 (4): 465–473. doi:10.1016/S0039-128X(68)80062-5. {{cite journal}}: Check date values in: |date= (help)
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