paper : 05 metabolism of lipids module: 10 types of lipids vi

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Biochemistry METABOLISM OF LIPIDS

Types of Lipids

Paper : 05 Metabolism of Lipids

Module: 10 Types of Lipids VI

Principal Investigator

Paper Coordinator and

Content Writer

Dr. Sunil Kumar Khare, Professor,

Department of Chemistry, IIT-Delhi

Dr. Suaib Luqman, Scientist (CSIR-CIMAP)

& Assistant Professor (AcSIR)

CSIR-CIMAP, Lucknow

Content Reviewer Prof. Prashant Mishra, Professor,

Department of Biochemical Engineering

and Biotechnology, IIT-Delhi

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Types of Lipids

DESCRIPTION OF MODULE

Subject Name Biochemistry

Paper Name 05 Metabolism of Lipids

Module Name/Title 10 Types of Lipids VI

Dr. Vijaya Khader Dr. MC Varadaraj

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Types of Lipids

1. Objectives

To know about the Steryl alkyl ethers, glycosides

What are the significance of Sterol sulfates

Occurrence and Importance of Cholesterol glucouronide, Alkyl glycosides and Polyglycosides

2. Concept Map

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Types of Lipids

3. 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 3-(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

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Types of Lipids

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.

Structure of β-Sitosterol β-D-Glucoside

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 g/ml), the respite part being removed into the bile.

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Types of Lipids

Structure of Cholesterol glucouronide

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--D-glucoside of -

sitosterol is the foremost type detected in tubers of potato (51%) whereas 6'-linoleoyl--D-

glucoside of -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.

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Types of Lipids

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.

Structure of Linckoside

Sterol Sulfate

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Types of Lipids

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.

Structure of Cholesterol sulfate

Squalamine which is a compression product of cholestane 24-sulfate with spermidine in the 3

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

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Types of Lipids

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.

Structure of Annasterol

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.

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Types of Lipids

Structure of Weinbersterol A

Sterol trisulfates are also found in sponges with positioning of sulfate groups at carbon 2, 3 and

6. They possesses remarkable antiviral and antibacterial properties and a compound from

Pseudoaxinissa digitata (Demospongia) revealed anti-HIV activity.

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Types of Lipids

Structure of Sterol trisulfate

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

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Types of Lipids

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.

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Types of Lipids

Structure of Ascarosides (n =23-30)

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.

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Types of Lipids

Structure of Cytopiloyne

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.

Structure of Simplexides

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.

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Types of Lipids

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.

Structure of Alkyl Polyglycosides

4. Summary

In this lecture we learnt about:

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Types of Lipids

The Steryl alkyl ethers, Steryl glycosides, Cholesterol glucouronide, Sterol sulphates, Alkyl glycosides

and Polyglycosides.

Their Occurence, Importance & Chemical and Biological Nature

paper : 05 metabolism of lipids module: 10 types of lipids vi

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