Types of Lipids V

Suaib Luqman

Objectives

v To know about the Phytosterols
v What are the significance of Phytosterols
v How they act in a system

Concept Map

3. Description

3.1 Types of Lipids V

Complex Lipids….

Phytosterols

In 1878, Hesse O isolated the first sterols from Phytostigma venenosum (Calabar beans) and coined the term ‘Phytosterine’. Later in 1906, Windaus and Hault named this substance as ‘Stigmasterol’. Thomas H proposed the term ‘Phytosterol’ in 1897 for vegetal derived sterols. Chemically, phytosterols have the identical structure as cholesterol but the side chain is tailored

by toting up of 1-2 carbon atoms at C24 with either a or b chirality. All phytosterols have 24 alkyl groups which are distinctive and conserved during ensuing metabolism of steroid in both plants and fungi to bestow hormones that control development and reproduction. Phytosterols has been found more competent than cholesterol in expanding the temperature dimension in which membrane-coupled biological action takes place as plants have to counter elevated temperature disparity than animals.

Mostly, phytosterols have 28-30 carbon units with 1-2 C=C double bonds, usually one in the nucleus of the sterol and occasionally a second in the side chain of alkyl residue. In plants, cycloartenol give rise to phytosterols whereas in fungi (including yeasts), vertebrates they derived from lanosterol through squalene cyclization. Facts also specifies the occurrence of biosynthetic pathway for phytosterol in plant cells through lanosterol and was chosen as the ‘Lanosterol Pathway’.

In plant species, over and above 250 diverse types of phytosterols have been identified and reported. Some of the envoys are campesterol, b-sitosterol and stigmasterol. b-Sitosterol is used for steroid synthesis; exist in the entire plant lipids.

Stigmasterol, also known as ‘Wulzen factor’, is needed for the synthesis of Vitamin D3 and progesterone. It is a potential anti-inflammatory compound that inhibits numerous matrix degradation and pro-inflammatorymediators implicated in cartilage degradation induced by osteoarthritis.

In brown algae, the prevailing sterol is fucosterol and cholesterol exists in diminutive amounts. Ergosterol (Mycosterol), is the C28 imperative sterol from ergot and yeast. Ergosterol was discovered by Tanret C followed by Gerard E who observed that fungi also have ergosterol. In yeast, Gerard was the first to identify ergosterol as a cell membrane component limited to fungi, and it could be applicable as an indicator molecule for these microbes in an existing biomass. Upon irradiation, ergosterol gives rise to calciferol (Vitamin D2).

Antrosterol (ergosta-7, 9, 22-trien-3b-ol), an isomeric form of ergosterol, from Antrodia camphorate (a fungus), is efficient in hepatoprotection via its anti-inflammation ability. This compound is used in Chinese traditional medicine for the treatment of cancer, diarrhoea, drug intoxication and hypertension.

EuroFIR-BASIS is exclusive online database containing information on the content of the selected phytosterols in plant based foods and different plants.

Phytosterols detailed for an extensive portion of total dietary sterols in vertebrates and generate a broad range of biological actions in humans and animals. They possess efficient cholesterol- lowering and anti-tumor properties, decreases serum β-carotene concentration, without varying vitamins A, D and E absorption.In brown algae like Sargassum ringgoldianum and Lessonia nigrescens (Phaeophyta), Saringosterol (a derivative of fucosterol) has been revealed to restrain the Mycobacterium tuberculosis growth comparable to that of rifampicin but without considerable toxicity against mammalian cells.

In 2004, the European Commission endorsed the toting up of phytosterols and phytostanols in food products with conditions of appropriate cataloging. Phytosterols similar to cholesterol undergo oxidative processes and the resultant oxyphytosterols have been revealed to display beneficial biological properties.

Phytostanols

Are fully saturated sub-group of phytosterols with no double bonds, produced by hydrogenation. They are found in very minute amounts in legumes, nuts and seeds but in high amounts in few cereal species. To advance their solubility, they combine with the esters of fatty acid to generate esters of plant stanol. Sitostanol is the utmost commonly found stanol and stanols frequently crop up in dinoflagellates, the chief source of 5a (H)-stanols in marine sediments.

In animals, fully saturated sterols of bacterial origin are conjointly established. 5b (H)-stanol and coprostanol, constitutes more or less 60% of the overall sterols in human faeces.

Phytosterols are of wide occurrence and its persistence in sediment has been reported in aged geological samples. The analysis, diversity and health-promoting uses of phytosterols and phytostanols have already been revealed and reviewed.

Stigmastanol, dihydrocholesterol and coprostanol are recurrently exist in sediments and occasionally utilized as biomarkers primarily for the existence of life in petroleum and sedimentary organic matter. The majority of steroids exist in sediments are C27-C29 steranes which are pivotal intermediates in the exchange of steroids (oxygenated) into steranes (saturated). In addition, a wide variety of sterenes (monounsaturated) have been detected in immature sediments. Marine demosponges created 24-Isopropylcholestane (hydrocarbon remnants of C30 sterols) accounted the charisma of Metazoa presence in the geological documentation during the Neo-proterozoic era (542-1,000 million years ago). This sterol symbolizes a powerful biomarker for early animal diversification and endows with the primeval facts for animals in the fossil record.

Sterol Esters

Sterols are often endowed esterified to fatty acids. In the tissues of animal (adrenals, liver, plasma), cholesterol is esterified by an array of fatty acids and recurrently by essential fatty acids, accordingly forming esters of cholesterol. Esters of sterol are vital but exceedingly erratic part of yeast cell with values varies from remnants to 50% of the total lipids.

In animals, the cholesterol esterification inside intestinal cells (acyl CoA cholesterol acyltransferase, ACAT) allocates the free cholesterol to be accumulated as a neutral lipid in cytosolic droplets and in the stuffing of cholesterol into lipoprotein particles for the export by means of the liver cells via plasma. The human meibomian glands secretions (sebaceous glands at the edge of eyelids) are predominantly rich in esters of cholesterol (~30% of the lipid puddle), exemplified by a monounsaturated or saturated fatty acid moiety with C18-34 carbon chain. Cholesteryl arachidonate and cholesteryl linoleate present in nasal fluid have been revealed to bequeath to the intrinsic antibacterial activity. Cholesteryl nitrolinoleate, a nitrated lipid perceived in human lipoproteins and blood plasma is a prospective marker of the chain breaking antioxidant role of nitric oxide radical during lipid peroxidation. Nitrated linoleic acid, a potent signaling molecule and a down regulator of inflammatory response revealed to be fundamentally enhanced after macrophage activation, signifying that nitration of lipid happens as part of the retort to inflammatory stimuli.

β-sitosteryl esters, stigmasteryl and ergosteryl are present in plant cell membranes and seed oils. Cycloartenol and esters of stigmasterol have been isolated from Bryophytes (Hepaticeae). In addition, cholesterol also forms ester linkages with secreted polypeptide and signaling molecules preset by the hedgehog gene family during the growth and development of metazoan. The details about sterol esters, their synthesis, storage and degradation have been well studied and reviewed.

Summary

In this lecture we learnt about:

The Phytosterols and Sterol Esters
Their Importance & Biological Significance

you can view video on Types of Lipids V

Weblinks

Books

1. Akhisa, T.; Kokke, W. 1991. Naturally occurring sterols and related compounds from plants. In Patterson, G. W.; Nes, W. D. Physiology and Biochemistry of Sterols. Champaign, IL: American Oil Chemists’ Society. pp. 172–228.

2. Phytosterols as Functional Food Components and Nutraceuticals by Paresh C. Dutta. 2003. https://books.google.co.in/books?isbn=0824758773

3. Phytosterol Antioxidant Activity and Effects on Shelf Life of Fluid Milk and Yoghurt Quality by Emefa Monu. 2007. https://books.google.co.in/books?isbn=0494261595

4. Handbook of Analysis of Active Compounds in Functional Foods by Leo M.L. Nollet, Fidel‎ Toldra. 2012. https://books.google.co.in/books?isbn=1439815909

5.The Food with Added Phytosterols Or Phytostanols (Labelling) (Wales) (Amendment) Regulations 2014 by Great Britain. https://books.google.co.in/books?isbn=0348108974

Journals

Woyengo, T A; Ramprasath, V R; Jones, P J H. 2009. Anticancer effects of phytosterols. European Journal of Clinical Nutrition 63 (7): 813-20.
Ostlund, Richard E. 2002. Phytosterols Inhumannutrition. Annual Review of Nutrition 22: 533– 49.
Ostlund RE Jr. Phytosterols and cholesterol metabolism. Curr Opin Lipidol. 2004 Feb; 15 (1): 37-41.
Moreau RA1, Whitaker BD, Hicks KB. Phytosterols, phytostanols, and their conjugates in foods: structural diversity, quantitative analysis, and health-promoting uses. Prog Lipid Res. 2002 Nov; 41 (6): 457-500.
Lampe, M.A.; A.L. Burlingame, J. Whitney, M.L. Williams, B.E. Brown, E. Roitman, and M. Elias. 1983. Human stratum corneum lipids: characterization and regional variations. J. Lipid Res. 24: 120–130.
Katan, MB; Grundy, SM, Jones, P, Law, M, Miettinen, T, Paoletti, R, Stresa Workshop, Participants. 2003. Efficacy and safety of plant stanols and sterols in the management of blood cholesterol levels. Mayo Clinic proceedings. Mayo Clinic 78 (8): 965–78.