Types of Lipids VI

Suaib Luqman

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  1. Objectives
  • v To know about the Steryl alkyl ethers, glycosides
  • v What are the significance of Sterol sulfates
  • v Occurrence and Importance of Cholesterol glucouronide, Alkyl glycosides and Polyglycosides
  1. Concept Map
  1. Description

3.1 Types of Lipids IV

 

 

Complex Lipids

 

 

Steryl Alkyl Ethers

 

First reported in sediments from Walvis Bay, steryl alkyl ethers exist in marine sediments till Cretaceous age. As per MS data, steryl alkyl ethers consist of C27-29 sterols alongwith 1-2 double bonds that are bound to ether at C8-9 alkyl chains or with one double bond and ether

 

bound to a C10-12 alkyl moiety. The structures of Cholest-5-enyl 3b-(3-dodecanyl) ether originated in Pleistocene Atlantic sediment. Occurrence in sediments with a high diatom suggests that unknown diatoms ought to be an unswerving biological resource.

Steryl Glycosides

Are also known as derivatives of Glycosylated Steryl produced by few bacteria, some animals, most plants and fungi. This family includes one carbohydrate unit (glucose, xylose and even arabinose) allied to the hydroxyl group of solitary sterol molecule (brassicasterol, campesterol, dihydrositosterol, sitosterol and stigmasterol). Helicobacter was exposed to be principally rich in cholesterol glucosides (~33% of total lipids) suggesting the importance of these molecules as chemotaxonomic markers. In Acholeplasma axanthum, a prokaryote, the presence of cholesterol  diglucoside has been reported suggesting that sterol glucosides take part in the cellulose synthesis. It exert as a substrate to generate superior homologues of the cellobioside type with β-1,4-linked glucosyl residues and the ensuing disaccharide is ripped off and utilized as a primer for auxiliary cellulose elongation.

Cholesterol glucuronide

 

 

It was sequestered from human liver (~33 nmol/g wet tissue). Hara et al., (1982) have alienated it from the acidic fraction of lipids and accentuated that it cannot be distinguished from ganglioside GM4 by TLC. They apparently orchestrated in the liver and enters the bloodstream

(~6 mg/ml), the respite part being removed into the bile.

 

Acylated Steryl Glycosides

 

 

When a fatty acid is acylated at the primary alcohol group of hexose (glucose or galactose) moiety, it results in the formation of steryl glycoside molecule. 6′-palmitoyl-b-D-glucoside of b-sitosterol is the foremost type detected in tubers of potato (51%) whereas 6′-linoleoyl-b-D-

glucoside of b-sitosterol is leading in extracts of soybean (47%). In these products, other fatty acids were also perceived (18:3, 18:1, 16:1) and further complex molecules were reported in Pistia stratiotes (an aquatic plant) where acetyl group (C2 & C4) acylates sitosterol glycosides adjacent to a stearyl (C6) residue on the sugar moiety. It has also been revealed that acylated steryl glucoside exist at a concentration between 1-125 mg/100 g fresh weight in vegetable parts including leaf, stem, root, tuber, fruit, cereals and the acylated form is 2-10 times more plentiful than non-acylated sterol glycoside. Sitosterol glucopyranoside acylated with linolenic or linoleic acid from Edgeworthia chrysantha was demonstrated to boast piscicidal activities killing Oryzias latipes in 2h at 100 ppm.

 

Sulfated Steryl Glycosides

 

In Linckia laevigata (Star Fish), numerous polyhydroxylated and sulfated steroid glycosides have been portrayed. Linckoside, a diglycoside compound possesses the most unusual chemical structure as xylopyranosyl with lone glycoside moiety and methyl xylopyranosyl as the other unit. Other homologue configuration but with only single glycoside moiety have been also depicted.

 

In marine invertebrates, over and above 70 sterol sulfates have been illustrated with compounds bearing 1-3 sulfate groups, coupled to the tetracycle core or to the side chain having characteristic antiviral and antibacterial activities. In mammalian cells, sulfate ester of cholesterol exist as cholesterol-3-O-sulfate in red blood cells and mostly in keratinized layers skin where it plays a role in the desquamation process.

 

Squalamine which is a compression product of cholestane 24-sulfate with spermidine in the 3b position was revealed in the stomach of shark and was revealed to be an efficient antimicrobial agent. It inhibits angiogenesis and endothelial cell proliferation and hence valuable for fight against numerous pathologies such as cancer and macular degeneration. This molecule act as immune effector in lower vertebrates and its presence in WBCs (immune cells) makes it pragmatic to contemplate that this molecule evolve in lower vertebrates.

In the mitochondria and nucleus of rat hepatocytes, cholesterol-3-O-sulfate (a sulfated oxysterol) hydroxylated on C25 has been reported at elevated levels. Afterward sulfated oxysterol has been revealed to be an effective switch of lipid metabolism in hepatocytes of  human and macrophages. Sterol mono, di and trisulfates have also been explained in invertebrates found in warm waters.

From Poecillastra laminaris (a sponge living in Philippines seawater), Annasterol, a sterol monosulfate, was sequestered possessing antibacterial properties against Bacillus vulgaris.

From Petrosia weinbergi (a sponge living in Bahamas waters), weinbersterols (sterol disulfates) was isolated depicting antiviral properties against VIH and the virus of cat leukemia and against.

 

Lembehsterols, another example was isolated from Petrosia strongylata (marine sponge) demonstrated inhibitory activity against thymidine phosphorylase, an enzyme allied to angiogenesis in solid tumors. These molecules are used as replica for increasing antiviral power in transformed structures.

 

iii.    Glycosides of fatty acids, alcohols or amino alcohols

 

In lower organisms (e.g. sponges), bacteria and yeasts simple glycolipids are present containing a glycosyl moiety (one or more units) allied to one hydroxyl group of a fatty alcohol or phosphoprenols (phosphorylated alcohol), a hydroxy fatty acid or to one carboxyl group of a fatty acid (ester linkage) or to an amino alcohol. They possess exciting physical or biological assets and few (e.g. alkyl glycosides) are industrially produced for their detergent properties. Complex glycosides are also produced by amide linkage amid a fatty acid and a glycosyl moiety and hence might be classified into following key groups.

  • O-glycosyl link or ester link
  • O-glycosyl link or N-acyl link

 

They are poised of a glycosyl moiety (one or more units) allied to the hydroxyl group of a fatty alcohol including either a branched chain or a normal chain or a phenolic alcohol. The glycosyl phosphopolyprenols are implicated in numerous reactions initiating glycosylation of protein.

 

 

Alkyl glycosides and Polyglycosides

 

Alkyl glucosides were isolated and deliberate in Anabaena cylindrical (nitrogen-fixing cyanobacteria) whereas in the heterocysts of cyanobacteria, they take part in the protection. Later some other structures were characterized and studied in additional species (Anamaeba torulosa, Cyanospira rippkae) with different chain length and functional groups. They contain sugar moieties glycosidically bound to keto-ols, keto-diols and long chain diols, triols. The aglycone moiety contains C26/C28 carbon chains along with hydroxyl groups at the C3, w1/w3 positions. Keto-ols and keto-diols enclosed their carbonyl functionalities aptly at C3 position. In Nostocaceae, alkyl glucosides were typified by the presence of C3 ketones and triols.

In the eggs and tissues of nematodes, Ascarosides have been described. In Parascaris equorum and Ascaris suum, it is formed by a glycosyl moiety (3,6-didesoxymannose, recognized as ascarylose) allied to a 2-hydroxylated hydrocarbon enclosed between 26 and 33 carbon units.

 

These compounds are supposed to be conscientious for providing chemical resistance to the eggs as they are plentiful in the internal layer of lipid in the eggshells of nematode. It is worth mentioning that ascarylose also exists in the LPS of Yersinia pseudotuberculosis, Pasteurella pseudotuberculosis, involved as pheromones in Caenorhabditis elegans.

In Bidens parviflora, a Chinese medicinal plant, polyacetylenic glucosides has been described, where the glucose unit is connected to an alkyl chain (10-14 carbon moiety) along with 2-3 acetylenic bonds and 1-2 hydroxyl groups. They are effective inhibitors of nitric oxide production and histamine release. Cytopiloyne, a closely related compound isolated from Bidens pilosa has been revealed to avert diabetes (type 1) in mice via T cell regulation. It has a diol with 13 carbons units and four triple bonds.

 

Simplexides, an odd glycolipids isolated from Plakortis simplex (Caribbean marine sponges), are poised of a long chain secondary alcohol (C34-C37 branched at one end) connected to disaccharide chain by the hydroxyl group. R1 and R2 outline the two ends with 17-19 carbon units of the aliphatic chain. They were revealed to be non-toxic to the cells and immunosuppressive by mechanism.

Since 1977, alkyl glycosides are used as the raw and starting material for the synthesis of surfactants.

In 1893, Fischer first reported the synthesis of alkyl polyglycosides by retorting anhydrous ethanol and glucose in the presence of HCl. In 1934, the tensioactive assets of alkyl polyglycosides were registered in the first patent. Similarly, N-methylglucamides are primed with methylamine by reductive amination and ensuing acylation. The alkyl glucosides are exceedingly efficient surfactants as cleansing agents, in washing and are extensively used in as auxiliaries in crop fortification formulations and cosmetic products.

 

 

The structure corresponds precisely to the surfactant model where the lipophilic (hydrophobic) hydrocarbon chain is formed by dodecanol/tetradecanol (fatty alcohol) from the oil of coconut and palm kernel. The utilization of alkyl polyglycosides in a shampoo or detergent allocate a reduction of the surfactants amount and have a superior compatibility with the mucous membranes, skin, eyes and besides being completely biodegradable.

4. Summary

 

In this lecture we learnt about:

 

  • The Steryl alkyl ethers, Steryl glycosides, Cholesterol glucouronide, Sterol sulphates, Alkyl glycosides and Polyglycosides.
  • Their Occurence, Importance & Chemical and Biological Nature
you can view video on Types of Lipids VI

Weblinks

 

www.sciencedirect.com/science/article/pii/S0146638012002240

 

http://dspace.library.uu.nl/handle/1874/22580

 

www.cyberlipid.org/sterols/ster0003.htm

 

http://link.springer.com/chapter/10.1007/978-3-642-66632-2_9

 

www.ncbi.nlm.nih.gov/pubmed/20138912

 

www.agqm-biodiesel.de/en/faq/…/study-on-steryl–glycoside-content/

 

http://pubchem.ncbi.nlm.nih.gov/compound/189039

 

www.nature.com/nchembio/journal/v11/n2/…/nchembio.1714_F5.html

 

http://www.ncbi.nlm.nih.gov/pubmed/12729666

 

www.youtube.com/watch?v=VOLu7gow_YE

 

 

 

Books

 

1.Ether Lipids chemistry and Biology by Fred Snyder. 2012. Page 162. https://books.google.co.in/books?isbn=0323149758

2.Ether lipids: Biochemical and Biomedical Aspects by H.K. Mangold. 2012. Page 80. https://books.google.co.in/books?isbn=0323149723

3.Clinical Lipidology: A Companion to Braunwald’s Heart Disease by Christie M. Ballantyne. 2009. Page 293. https://books.google.co.in/books?isbn=1416054693

4.Marine Natural Products V2: Chemical And Biological Perspectives by Poul Schever. 2012. Page 109. https://books.google.co.in/books?isbn=0323151868

 

 

Journals

 

  1. Raquel A. Lopes dos Santos, Patrick De Deckker, Jaap S. Sinninghe Damsté, Stefan Schouten. 2013. A late Quaternary sedimentary record of steryl alkyl ethers from offshore southeastern Australia. Organic Geochemistry 54: 140-145.
  2. Stefan Schouten, Sebastiaan W. Rampen, Jan A.J. Geenevasen, Jaap S. Sinninghe Damste. 2005. Structural identification of steryl alkyl ethers in marine sediments. Organic Geochemistry 36: 1323-1333.
  3. Nyström, L., Schär, A. and Lampi, A.-M. 2012. Steryl glycosides and acylated steryl glycosides in plant foods reflect unique sterol patterns. Eur. J. Lipid Sci. Technol., 114: 656-669.
  4. W. Eichenberger. 1977. Steryl Glycosides and Acylated Steryl Glycosides. Lipids and Lipid Polymers in Higher Plants. pp 169-182
  5. Wade AP. 1970. The estimation of cholesterol sulphate and cholesterol glucuronide in plasma. Clinica Chimica Acta27: 109-116.