Lipids: Pharmacognosy MANIK

Lipids: Pharmacognosy
Prepared by: Shadid Uz Zaman At Tadir; B.Pharm. ;M.pharm.; DU Page 1
Arrangement: Md. Imran Nur Manik; B.Pharm. M.Pharm.;RU
Lipids are the fat or fat like substances which occur in plants and animals.
Like the carbohydrates and proteins, the lipids constitute a very important group of organic
substances from the standpoint view of physiological utilization. Unlike the carbohydrates and
proteins, the lipids comprise a heterogeneous group of substances in terms of chemical
composition.
They are grouped together primarily on the basis of solubility characteristics.
In general, they are soluble in the usual fat solvents such as ether and chloroform and are
insoluble in water.
One common property of lipid is that they are hydrophobic in nature.
Definition:
Lipids are a broad group of molecules which are esters of long-chain fatty acids and
alcohols, or of closely related derivatives. This includes Fixed oils, fats and Waxes.
Classification:
The lipids may be divided into five classes according to their chemical structure.
1. Fixed oil and fats
2. Waxes
3. Sterols
4. Phospholipids
5. Glycolipids
Fixed oils and fats: They are esters of glycerol and fatty acids. They are obtained either from
plants or animals. Their primary function is food storage.
Examples are Coconut oil, Lard etc.
Waxes: These are esters of high molecular weight monohydric alcohols and high molecular
weight fatty acids.
Examples are beeswax, carnauba wax etc.
Sterols: They are alcohols containing the cyclopenteno-phenanthrene nucleus.
Examples are cholesterol, ergosterol etc.
Phospholipids: These are esters consisting of glycerol in combination with fatty acids,
phosphoric acid and certain nitrogenous compounds.
Examples are Lecithin, Cephalin etc.
Glycolipids: These are substances isolated from the brain and from various other substances
which on hydrolysis yield fatty acids, galactose and a nitrogenous compound.
Examples are Phrenosin, Kerasin etc.
Md.
Imran
Nur
Manik

Fixed oils, fats and waxes
Fixed oils: They are esters of glycerol and fatty acids.
Waxes: They are esters of high molecular weight monohydric alcohols and high molecular
weight fatty acids.
Fatty acids: They are monobasic acids derived from fixed oils, fats and waxes. Most of them
are C10 to C20 straight chain (aliphatic) compounds.
They may be saturated e.g. Palmitic acid or unsaturated e.g. Oleic acid.
Some fatty acids are cyclic compounds e.g. Hydnocarpic acid.
The important fatty acids are listed below
Saturated:
Name Formula
Caproic acid CH3(CH2)4COOH
Caprylic acid CH3(CH2)6COOH
Capric acid CH3(CH2)8COOH
Lauric acid CH3(CH2)10COOH
Myristic acid CH3(CH2)12COOH
Palmitic acid CH3(CH2)14COOH
Stearic acid CH3(CH2)16COOH
Arachidic acid CH3(CH2)18COOH
Unsaturated:
NAME FORMULA
Oleic acid CH3(CH2)7CH=CH(CH2)7COOH
Linoleic acid CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH
Linolenic acid CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
Ricinoleic acid CH3(CH2)5CHOHCH2CH=CH(CH2)7COOH
Differences between fixed oils and fats:
 Fixed oils and fats differ only as to melting point; those that are liquid at normal temperature
are known as fixed oils, while those that are semisolid or solid at normal temperature are known
as fats.
 Also there is no chemical difference between fats and fixed oils of plant or animal origin.
 Most vegetable oils are liquid at normal temperature and most animal fats are solid.
But there are some notable exceptions, such as cocoa butter, a solid vegetable oil and cod liver
oil, a liquid animal fat.
Tests for fixed oils and fats:
There are several tests for fixed oils and fats by means of which their identity, quality and purity
may be determined.
These tests are based upon the chemical composition/constitution of the fatty acids.
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Imran
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Manik

 Acid value or acid number:
It indicates the amount of free fatty acids present in the oil. It is the number of milligrams of
Potassium hydroxide (KOH) required to neutralize the free fatty acids in 1g of the substance.
 Saponification value:
It indicates the number of milligrams of Potassium hydroxide (KOH) required to saponify
completely 1g of fat or oil. Ester value is the difference between the saponification value and
acid value.
 Reichert-Meissl number:
It is the number of milliliters of 0.1N Potassium hydroxide (KOH) solution required to
neutralize the volatile water soluble acids obtained by hydrolysis of 5g of fat or oil.
Iodine number
It indicates the degree of unsaturation. It is the number of grams of Iodine absorbed under
prescribed condition by 100g of the substance.
Other physical constant such as melting point, specific gravity, refractive index etc. also serve
as identity, purity and quality test.
Sources of vegetable oils and fats:
Vegetable oils and fats may occur in various parts of the plant, but as a general rule, seeds
contain larger quantities of fixed oils than other plant parts. Therefore seeds are usually used as
the sources of fixed oils.
For example, cotton seed, linseed, coconut, castor beans, almond etc.
In a few instances, other plant parts yield considerable quantities of fixed oil, e.g. pericarp of the
olive. In certain Fungi (e.g. Ergot), fat is the characteristic reserve food material.
Extraction of fixed oils and fats:
Fixed oils and fats of vegetable origin are obtained by expression in hydraulic presses.
If the expression is carried out in the cold, the oil is known as ‘virgin’ or ‘cold pressed’ oil.
In contrast if the expression is carried out in heat, the oil is known as ‘hot pressed’ oil.
Sometimes organic solvents are used for the extraction of oils.
Animal fats are separated from other tissues by rendering with steam, with or without pressure.
The heat melts the fat which rises to the top. The liquid fat is then separated by decantation.
It may be further clarified by filtration and bleached with ozone.
Stearin is often removed from fats by chilling and filtration.
Chemistry of fixed oils and fats:
Fixed oils and fats are-
 Glycerides of fatty acids (simple or mixed)
 More specifically triacyl glycerols
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Imran
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Manik

Simple glycerides: All the fatty acid groups are identical such as Olein, Palmitin or Stearin.
Palmitic acid: CH3(CH2)14COOH
Stearic acid: CH3(CH2)16COOH
Oleic acid: C17H33COOH
Mixed glycerides: Fatty acid groups are different.
Example of mixed glycerides: 1-oleo-3-palmito-2-stearin
1-oleo-3-palmito-2-stearin
Glycerides of unsaturated fatty acids are liquid
Glycerides of saturated fatty acids of sufficient chain length are solid.
Configuration of double bonds in the unsaturated fatty acids is cis rather than trans.
Coconut oil:
It is the fixed oil obtained from the seeds of Cocos nucifera (Family: Palmae)
The palm grows in the coast regions of all tropical countries.
Fresh kernel contains 30-40% of oil
Dried kernel (Copra) contains 65% of oil.
Extraction from copra:
Expressed without heat results in obtaining copra olein, a thinner oil.
Further expression with more pressure yield copra stearin.
Constituents:
A mixture of triglycerides
Fatty acid components such as Lauric, Myristic Palmitic, Caprylic, Capric, Oleic and
Stearic acid.
The oil may have an unpleasant odor due to small amount of free caprylic acid.
Uses:
Pharmaceutical: Used as ointment bases
Commercial: Extensively used in chocolate, candy, soap, hair dressing and other cosmetics.
Md.
Imran
Nur
Manik

Linseed oil:
It is the fixed oil obtained from the dried ripe seed of Linum usitatissimum (Family:
Linaceae). It is an annual herb cultivated in temperate and tropical regions.
Extraction of the oil:
Linseed contain 30-40% of fixed oil
Constituents:
Fatty acid components which are mainly unsaturated like
i) Linolenic acid (36-50%),
ii) Linoleic acid (23-24%) &
iii) Oleic acid (10-18%)
It also contains small amount of saturated fatty acid (5-11%) such as myristic acid, palmitic acid
and stearic acid.
Uses:
External use: Used in liniments. Hydrolysed linseed oil is very effective against Staphylococcus
aureus strains resistant to antibiotics.
Internal use: As laxative and demulcent.
Commercial use: In the manufacture of soaps, printers ink, oil cloth etc
Peanut oil:
It is the fixed oil obtained from the seed of Arachis hygaea (Family: Leguminosae), an ever
green tree cultivated in Mediterranean countries.
Constituents:
Fatty acid components which are
i) Oleic acid (50-65%)
ii) Linoleic acid (18-30%)
iii)Palmitic acid (8-10%) &
Other acids 10-12%. These are Arachidic, Stearic, Behenic and Lignoceric acid.
Uses:
Used as a solvent for intramuscular injection.
In the production of margarine, cooking fat, etc.
Md.
Imran
Nur
Manik

Chaulmoogra oil / Hydnocarpus oil:
It is the fixed oil obtained from the seed of Hydnocarpus wightiana, H. anthelmintica, H.
heterophylla and other species of Hydnocarpus and also of Taractogenos kurzii (Family:
Flacourtiaceae)
The plants are tall trees found in Burma and eastern india.
The oil is cold pressed from the kernels of the seed.
Constituents:
i) Hydnocarpic acid (48%)
ii) Chaulmoogric acid (27%)
iii) Gorlic acid.
Uses:
The fatty acids possess specific toxicity for Micobacterum laprae and Micobacterum
tuberculosis.
The oil was used in the treatment of leprosy and tuberculosis but now organic sulfones
have replaced the oil.
Castor oil:
It is the fixed oil obtained from the dried ripe seed of Ricinus communis (Family:
Euphorbiaceae)
It is an annual herb in temperate regions or a tree attaining the height of 15 meters in the
tropics. The plant is indigenous to India and is extensively cultivated in India, Brazil, the USA
and various parts of Africa.
The remainder of the oil is solvent extracted, yielding a darker lower grade oil.
Md.
Imran
Nur
Manik

Constituents:
A mixture of triglycerides about 75% of which is triricinolein.
The remainder consists of diricinileoglycerides. The third acyl group may be either oleic,
linoleic, palmitic or stearic acid.
Uses:
Pharmaceutical use:
1. Cathartic: The cathartic action is due to the free ricinoleic acid which is produced by
hydrolysis in the duodenum.
2. Hydrogenated castor oil is used as a stiffening agent in some pharmaceutic formulations.
Commercial use: In the manufacture of soaps, paints, varnishes, plasticizers and lubricants.
Olive oil:
It is the fixed oil obtained from the ripe fruit of Olea europaea (Family: Oleaceae), an
evergreen tree cultivated in the Mediterranean countries, the USA and other subtropical
regions.
Olive oil is available in the market in several grades which greatly depends on the extraction
process.
Virgin oil is obtained by gently pressing the peeled pulp freed from the endocarp. It is rarely
exported.
First and second grade of olive oil are obtained by pressing the crushed pulp with less
pressure and then with more pressure.
Technical oil is obtained by mixing the same pulp with hot water and pressing again.
Sulfur olive oil (inferior quality) is obtained by extracting the pulp with carbon disulfide.
Constituents:
i) Oleic acid (65-75%)
ii) Palmitic acid (10-15%)
iii) Linoleic acid (9-15%)
Uses:
Pharmaceutical use: Olive oil is classed as a pharmaceutic aid. It is a laxative, demulcent,
emollient and a nutrient. It is widely used as a salad oil.
Commercial use: In the manufacture of soaps, plasters etc.
Beeswax:
It is the purified wax obtained from the honey comb of the bee, Apis mellifera (Family:
Apidae).
Wax is secreted by worker bees in cells on the ventral surface of the last four segments of their
abdomen. The wax excretes through pores in the chitinus plates and is used by the young
worker bees to form the comb.
Md.
Imran
Nur
Manik

Preparation of yellow beeswax: After removal of the honey, the comb is melted in water, then
cooled and remelted and finally strained and allowed to harden in molds.
Preparation of white beeswax: It is prepared from yellow beeswax by treatment with charcoal,
potassium permanganate, chromic acid, chlorine, etc or by the slow bleaching action of light,
air and moisture.
Bleaching of yellow wax by light, air and moisture:
Constituents:
Alkyl esters of fatty and wax acids (about 72%).
The principal constituent is myricyl palmitate, C15H31COOC30H61
It also contain free wax acids (14%) especially cerotic acid C26H53COOH and its
homologs.
hydrocarbon (12%), Cerolein (an aromatic compound),
Other minor constituent include moisture, pollen and propolis (bee glue)
Uses:
Yellow wax is used as stiffening agents, as a base plasters.
White beeswax is used in ointments and cold creams.
Carnauba Wax:
Carnauba Wax is obtained from the outer waxy coating of the leaves of Copernicia cerifera
(Family: Plamae).
The palm grows from northern Brazil to Argentina. The leaves are collected twice a year in
September and December.
The wax is removed from the leaves with mechanical beaters and purified to remove
foreign matter.
Uses:
Pharmaceutical use: As a tablet coating agent and in place of beeswax.
Commercial use: in the manufacture of candles and leather polish.
Md.
Imran
Nur
Manik

Lipids: Pharmacognosy MANIK

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