Lipids

Lipids
Structurally diverse group of molecules insoluble in water, but dissolve in organic solvents such as chloroform, ether and alcohols. Wide variety of fatty-acid derived compounds, many pigments and secondary compounds unrelated to fatty acid metabolism.

LIPIDS
Simple: fixed oils, fats, waxes Complex: phosphatides, lecithins
may contain P, N as well as C, H, O

widely distributed in plant and animal kingdom

in all living cells sometimes accumulate to be commercially useful
plants - food reserve (fruit and seeds) animals insulation, energy sources, protection

Lipids or fatty esters are an important group

long chain fatty acid + alcohols eg glycerol

Lipids are non-polar (hydrophobic) compounds, soluble in organic solvents.

Most membrane lipids are amphipathic, having a non-polar end and a polar end.
Fatty acids consist of a hydrocarbon chain with a carboxylic acid at one end. A 16-C fatty acid: CH3(CH2)14 COO

Non-polar

polar
C atoms 9-10 may be

A 16-C fatty acid with one cis double bond between represented as 16:1 cis D9.

Nutritional importance of Lipids

Lipids are important dietary constituents, in terms of energy they provide, essential fatty acids and energy (9 cal/gm) whereas carbohydrate provide 4.5 cal/gm. Lipids are the carrier of the oil soluble vitamins A,D,E, and K.

CLASSIFICATION OF LIPIDS

LIPIDS

Simple lipids Phospho lipids

Complex lipids Derivative of lipid

Oil & fats( glycerides)

waxes

glycolipids

Choline Soya lecithin(polar lipids of plants)

Galactose lipid

Drying oil

Semi drying oil

Nondrying oil

fats Sal fat mahua fat/ tallow

Lindseed Sunflower

Rape seeds sesame

Castor oil, Palm oil, Peanut oil

Oils and Fats

Lipids can be classified based on physical properties at room temperature: Fats Oils Solid Liquid

Structurally fats and oils consist of two main components: Fatty acids and Glycerol.

Lipid - Constituents

Fatty Acids

Double bonds in fatty acids usually have the cis configuration. Most naturally occurring fatty acids have an even number of carbon atoms.

a 2

O C
1

fatty acid with a cis-D9 double bond

Some fatty acids and their common names: 14:0 myristic acid; 16:0 palmitic acid; 18:0 stearic acid; 18:1 cisD9 oleic acid 18:2 cisD9,12 linoleic acid 18:3 cisD9,12,15 a-linonenic acid 20:4 cisD5,8,11,14 arachidonic acid 20:5 cisD5,8,11,14,17 eicosapentaenoic acid (an omega-3)

Fatty Acid Structure

Lipid - types
1. Triacylglycerols Storage lipids Seeds, pollen

2. Phospholipids Membranes Amphipathic hydrophobic and hydrophilic groups.

3. Galactolipids - plastid membranes - galactosyl or sulfoquinovosyl group on the third carbon, high percent of polyunsaturated fatty acids; Peas 18:; Spinach 16:3 4. Sphingolipids not esters of glycerol but long chain amino alcohol that forms an amide linkage to fatty acids, acyl group is longer than C18 Plasma membrane

Glycerophospholipids
Glycerophospholipids (phosphoglycerides), are common constituents of cellular membranes. They have a glycerol backbone. Hydroxyls at C1 & C2 are esterified to fatty acids.
An ester forms when a hydroxyl reacts with a carboxylic acid, with loss of H2O.

CH2OH H C OH

CH2OH

glycerol

Formation of an ester:
O R'OH + HO-C-R" O R'-O-C-R'' + H2O

Phosphatidate
O O R1 C O H2C CH H2C O O C O P O O R2

phosphatidate

In phosphatidate: fatty acids are esterified to hydroxyls on C1 & C2 the C3 hydroxyl is esterified to Pi.

O O R1 C O H2C CH H2C O O C O P O O X R2

glycerophospholipid

In most glycerophospholipids (phosphoglycerides), Pi is in turn esterified to OH of a polar head group (X): e.g., serine, choline, ethanolamine, glycerol, or inositol. The 2 fatty acids tend to be non-identical. They may differ in length and/or the presence/absence of double bonds.

O O R1 C O H2 C CH H2 C O O C O P O OH H OH OH H H H OH O H OH R2

phosphatidylinositol

Phosphatidylinositol, with inositol as polar head group, is one glycerophospholipid. In addition to being a membrane lipid, phosphatidylinositol has roles in cell signaling.

Cholesterol, an
important constituent of cell membranes, has a rigid ring system and a short branched hydrocarbon tail.

HO

Cholesterol

Cholesterol is largely hydrophobic.

But it has one polar group, a hydroxyl, making it amphipathic.

PDB 1N83

cholesterol

Chemical tests Oils and Fats

solubility freezing point, melting point refractive index (and sometimes optical rotation) density

volatile acidity, unsaponifiable matter, acetyl value

Oleochemicals

Overview of possible reactions in oleochemistry

Production of fatty acids

Fatty acids, soaps

Mainly from coconut oil, palm kernel oil, Non edible oils. Major use in body care products and cosmetics Their salts with metal ions like Ca, Mg are sparingly soluble in water and create problems with precipitation

Derivatives of fatty acids

Monoglycerides

Commercial Sugar based Surfactants

Sorbitan esters, more or less ethoxylated (Tween, Span) n Sucrose esters n Alkyl Polyglucosides n Alkyl Glucamides

Biosurfactants
Hydroxylated and crosslinked fatty acids (mycolic acids) Glycolipids Polysacharide-lipid complexes Lipoproteins-lipopeptides Phospholipids

Lecithins, phospholipids, phosphatides

Generic name phospholipids
Lecithin in a narrower sense = phosphatidylcholine Produced from vegetable raw materials, e.g. soy bean oil

Areas for use of Lecithin

Emulsifier, wetting agent, dispersing agent O/W or W/O, relation to emulsifier structure In nature components in membranes Important parts of our food Applications Food industry, butter, margarine, cocoa, chocolate, caramels, toffee, bakery products Cosmetics

Crude lecithin
Mixture of 65% phospholipids and 35 % oil Minor amounts of other substances
Chemically modified lecithin:

Acetylated, hydroxylated, hydrolyzed

Waxes
Waxes are complex mixtures of fatty acids linked to long-chain alcohols. Waxes comprise the outermost layer of leaves, fruits, and herbaceous stems and are called Epicuticular waxes. Waxes embedded in the cuticle of the plant are cuticular waxes. Cutin is another wax in the cuticle and it makes up most of the cuticle. Suberin is a similar wax that is found in cork cells in bark and in plant roots. Both help prevent water loss by the plant. Structures of waxes vary depending on which plant produced them. Waxes are usually harder and more water repellant than other fats.

Waxes
contain appreciable quantities of
esters derived from higher monohydric alcohols (one OH group) of the methyl alcohol series combined with fatty acids (C16 C32)

most are solids at room temperature

can only be saponified by alcoholic alkali often contain free acids, hydrocarbons, free alcohols and sterols saponification and acid values higher, iodine values lower

commercially important examples

Vegetable: carnuba Animal: spermaceti, beeswax, wool wax

WAXES:

These are ester of fatty acids with high molecular weight monohydric alcohol such as octacosanol, cetyl alcohol, melissic alcohol etc. Waxes are in soluble in water but soluble in most organic solvent. These obtained from plant & animal sources: A) Plant Wax: Sisal wax, carnuba wax, bayberry wax.

B) Animal wax: Bees wax, wool wax,

Waxes saponified by alcoholic alkali, where as oils & fat, are saponified by aqueous alkali or alcoholic alkali C15H31 COOC16 H31 + KOH C16 H33 OH + C15 H31 COOK

Cetyl palmiate

Cetyl alcohol

Pottasium palmitate

 Carnuba wax
an adulterate of beeswax From the cuticle of the South American palm Copenicia cerifera Used in tablet coatings

Spermaceti
From the head of sperm (Physeter macrocephalus) and bottle-nosed whales (Hyperodon rostratus) just above right nostril) 500lb from 1 whale simple esters of cetyl alcohol CH3(CH2)4CH2OH cetyl palmitate, cetyl myistate 90-93% no longer used pharmaceutically, can be replaced by jojoba oil

Jojoba Wax

 Wool wax (Lanolin)

From the wool of sheep (Ovis aries) Complex composition:
Long chain fatty esters esters of cholesteryl and isocholesteryl + estolidic 32-33% esters of normal aliphatic alcohols with fatty acids 48-49%

Used as an emollient base for creams and ointments

major component of most ointments melting point 30-42oC readily absorbed through skin absorbs twice its own weight in water so makes an emulsion

Type of Oil Seed Extraction

- Animal Driven Ghani - Power Ghani - Screw press oil expeller - Hydraulic Press - Domestic method by boiling water -Solvent Extraction -Enzymatic Extraction Enzyme in cells can break down oils in cells some oils highly unsaturated and easily oxidized heat in air > rapid oxidation

Traditional Indian Ghani for oilseed crushing

Extraction efficiency about 65%

Power Ghani

Extraction efficiency 65 to 70%

Traditional Mechanical Oil Expeller

Extraction efficiency 70 to 75 % Double crushing

Cold Press Extraction

Castor beans
roll to break down testa winnow to separate seed coat from seed

Olives
put into press light pressure applied gives the 1st grade oil used in pharmacy oil washed to remove pigment floats to the top and is skimmed off 30-40% oil recovered not economical

Extraction efficiency 80 % Single crushing

Steam treatment + expression

material left from cold press undergoes steam treatment
repressed to get 2nd fraction of oil

Solvent extraction
to get 100% of oil out last portion gives a low grade used to industrial paints etc left with high protein+fibre fed to animals once ricin removed

Arachis oil
From seeds of Arachis hypogaea (Leguminosae) groundnut cultivated in tropical Africa, India, Brazil, southern USA and Australia

worlds 4th largest source of a fixed oil

seeds contain 40-50% oil fruits shelled by a machine kernels difficult to express; crushed and cooked at low pressure seed cake fed to cattle

 Composition:
oleic acid ~ 60% linoleic acid 24% palmitic acid 9% arachidonic acid

GU3, GSU2 like olive oil

acid and saponification values similar to olive oil

if fatty acids are separated (hydrolysis) the presence of arachidonic acid gives a melting point >710C
used as a test for adulteration of olive oil

Castor oil
From seeds of Ricinus communis (Euphorbiaceae) India, Africa, Europe Contains ricinoleic acid 91%, glycerides GU3
must be free of ricin

pale yellow, very viscous, acrid tasting soluble in ethanol (unlike most oils) due to so much hydroxy- acid Used in toothpaste, nail varnish remover, lubricant industry and pharmacy (as derivatives)