Lipids are esters of long-chain fatty acids and alcohols, typically glycerol. Ex- fixed oils, fats, waxes etc. In general, lipids are soluble in the usual fat solvents such as- ether, chloroform and are insoluble in water. They are hydrophobic in nature. The chief difference among fixed oils, fats and waxes is the type of alcohol present in it- In fixed oils and fats, glycerol combines with the fatty acids. In waxes, monohydric alcohol combines with fatty acids which has a higher molecular weight, e.g., cetyl alcohol [CH3(CH2)15OH]. They have a high-energy value (25% of body needs) and they provide more energy per gram than carbohydrates and proteins. Supply the essential fatty acids that cannot be synthesized by the body. Supply the body with fat-soluble vitamins (A, D, E and K). Tissue fat (phospholipid in nature) is an essential constituent of cell membrane and nervous system. Stored lipids as “depot fat” is stored in all human cells acts as: A store of energy. Protect internal organs from outside shocks. Act as subcutaneous thermal insulator against loss of body heat.

2. Lipids are esters of long-chain fatty acids and alcohols, typically glycerol. Ex- fixed oils,
fats, waxes etc.
In general, lipids are soluble in the usual fat solvents such as- ether, chloroform and are
insoluble in water. They are hydrophobic in nature.
The chief difference among fixed oils, fats and waxes is the type of alcohol present in it-
 In fixed oils and fats, glycerol combines with the fatty acids.
 In waxes, monohydric alcohol combines with fatty acids which has a higher
molecular weight, e.g., cetyl alcohol [CH3(CH2)15OH].
CH2
R
Fatty alcohol
OH C R
Fatty acid
HO
O
+
H2O
CH2
R O C R
O
Esterase (lipase) ester (lipid)

3. Biological Importance of Lipids:
 They have a high-energy value (25% of body needs) and they provide more energy per
gram than carbohydrates and proteins.
 Supply the essential fatty acids that cannot be synthesized by the body.
 Supply the body with fat-soluble vitamins (A, D, E and K).
 Tissue fat (phospholipid in nature) is an essential constituent of cell membrane and
nervous system.
 Stored lipids as “depot fat” is stored in all human cells acts as:
 A store of energy.
 Protect internal organs from outside shocks.
 Act as subcutaneous thermal insulator against loss of body heat.

4. The lipids may be divided into five classes according to their chemical structure-
1. Fixed oils & Fats
They are esters of glycerol with fatty acids, e.g. Olive oil.
Fixed oils are liquid at room temperature, whereas fats are semisolid or solid at ordinary
temperature. Most of the vegetable oils are liquid at ordinary temperature & most animal
fats are solid.

5. Fixed oils
Fats
1. Majority of the fixed oil contains
unsaturated fatty acids.
1. Mostly contain saturated fatty
acids.
2. Liquid at room temperature
2. Solid at room temperature
3. Lower melting point
3. Higher melting point

6. 2. Waxes
Esters of high molecular weight fatty acids with high molecular weight monohydric
alcohols, e.g. Spermaceti, beewax etc.
3. Sterols
Alcohols containing the Cyclopentanoperhydrophenanthrene nucleus. e.g. Cholesterol,
Ergosterol.
Cyclopentanoperhydrophenanthrene
nucleus
Cholesterol

7. Phospholipids
4) Phospholipids (Phosphatides)
Esters consisting of glycerol in combination with fatty acids, phosphoric acid & certain
nitrogenous compounds, e.g. Lecithin.
5. Glycolipids (Cerebrosides)
These are lipid substances containing fatty acids,
carbohydrates & nitrogenous compound. e.g. Phrenosin,
Kerasin. Since, the sugar moiety is usually galactose,
the glycolipids sometimes are referred to as
galactolipids. At present, they have no pharmaceutical
application.

8. Phospholipids Glycolipids

9. Physical Properties
1) Solubility: Lipids are insoluble in water but readily soluble in organic solvents.
2) Melting point: Fats have high melting point than oils.
3) Specific gravity: Generally they have lower density than water.
4) Spreading behavior: When a liquid lipid (oil) is poured on water, it spreads over water surface and reduces
the surface tension of water.
Chemical properties
1) Hydrolysis: Hydrolyses into fatty acids & glycerol with application of heat or by boiling with acid or alkali.
2) Rancidity: Rancidity is a chemical change that causes partial hydrolysis and a subsequent liberation of
volatile fatty acids; e.g. butyric acid from butter.
3) Hydrogenation: Lipids containing unsaturated fatty acids are generally liquid at room temperature and are
hydrogenated to convert them to semisolid fats.
4) Oxidation: Unsaturated fatty acids may undergo oxidation to form a number of oxygenated derivatives
including aldehydes, ketones etc.

10. Fixed oils are esters of fatty acid with glycerol. These may be-
 Monoglycerides
 Diglycerides
 Triglycerides

11. 1. Soap manufacture
2. Production of suppositories
3. Tablet coating
4. Dietary supplements
5. Emulsifying agents
6. Manufacture of paints, varnishes and lubricants
7. Therapeutic uses (e.g. castor oil, peanut oil)

12. 1) Castor oil
2) Olive oil
3) Peanut oil
4) Coconut oil
5) Mustard oil
6) Linseed oil

13. Castor oil is a pale yellowish or almost colorless transparent liquid with a
characteristic taste.
Botanical origin: Castor bean or castor oil seed is the ripe seeds of Ricinus
communis
Family: Euphorbiaceae
Plant part used: seeds

14. Constituents:
Castor oil is composed of a mixture of triglycerides
 Triricinolein ( 75% )
 Glycerides of- a) Oleic acid
b) Ricinoleic acid
c) Linoleic acid
d) Stearic acid
Uses:
 Stimulant cathartic (15-60 mL).
 Emollient.
 Preparation of zinc and castor oil ointment.
 Sterilized castor oil as soothing agent in eye.
 Oily vehicle for eye drops.
Triricinolein

15. Olive oil is a pale yellow or light greenish yellow liquid with a mild but
characteristic odor.
Botanical origin:
Olive oil is the fixed oil obtained from the ripe fruits of Olea europaea.
Family: Oleaceae
Plant part used: Ripe fruit
Constituents:
Glycerides of-
• Oleic acid (75%)
• Linoleic acid (9%)
• Stearic acid
• Arachidic acid
• Palmitic acid (10%)

16. Uses:
Laxative.
Nutrient.
Emollient.
Demulcent (an agent that forms a soothing film over a mucous
membrane, relieving minor pain and inflammation).

17. Peanut oil is the refined fixed oil obtained from the seed kernels of Arachis hypogaea
Family: Leguminosae
Plant part used: Seeds
Constituents:
Glycerides of
 Oleic acid (50-65%)
 Linoleic acid (18-30%)
 Palmitic acid (8-10%)
 Stearic acid, Behenic acid, Arachidic acid and Lignoceric acid (together 10-12%)

18. Uses:
Vehicles in emulsions, liniments, plasters, soap.
Ink manufacture.
Preparation of hydrogenated vegetable oil.
Botanical origin:
Coconut oil is obtained from dried solid part of endosperm of Cocos nucifera
Family: Palmae
Plant part used: Dried solid part of endosperm

19. Constituents:
Glycerides of-
• Lauric acid (50%)
• Myristic acid (20%)
• Capric acid
• Caprylic acid
• Caproic acid
• Oleic acid
• Palmitic acid
• Stearic acid
Uses:
 Confectionaries
 Cosmetics
 Ointment base

20. Botanical origin: Brassica juncea
Family: Cruciferae
Part used: Seeds
Constituents:
Glycerides of-
• Linoleic acid
• Oleic acid
• Erucic acid
Uses:
 Cardioprotective effects
 In the preparation of liniments (a medicated topical
preparation for application to the skin. Also known as
balm).
 As a topical treatment for inflammatory conditions such as
arthritis and rheumatism.
 Traditionally been used as an emetic and diuretic.
 Immunity Booster.

21. Botanical origin:
Linum usitatissimum
Family: Linaceae
Part used: Ripened seeds
Constituents:
• 9-10% of saturated fatty acids
(palmitic and stearic acid),
• 20% monounsaturated fatty
acids (mainly oleic acid),
• 70% alpha-linolenic fatty acid
Uses:
 It has emollient, expectorant, diuretic,
demulcent, and laxative properties.
 To reduce cholesterol and blood sugar.
 Treat digestive conditions.
Also known as flaxseed oil, is a colourless to yellowish oil.

22. Like fats, waxes are also esters of fatty acids. The alcohol, however, is not glycerol but
usually a long-chain, high-molecular weight alcohol.
In plants, waxes are generally found covering the external parts like the epidermis of
leaves and fruits, where their main function is to prevent the loss of water.
Wax is also produced by insects. e.g. the honeycombs of bees.
Uses:
Wax is used to make soft ointments harder.
The technical uses of waxes are substantial as in shoe
polishes and car waxes.

23. Botanical source:
Bees wax or yellow wax is the purified wax obtained from the honeycomb of the bee
Apis mellifera.
It is a solid varying in color from yellow to greenish brown.
Family: Apidae
Plant part used: Honeycomb
Constituents:
The wax consists of –
Esters of fatty & wax acids (72%), chiefly myricyl palmitate.
Free wax acids (14%), chiefly cerotic acid
Hydrocarbons( 12%)

24. Uses:
In foods and beverages, white beeswax and beeswax absolute (yellow beeswax
treated with alcohol), are used as stiffening agent.
Component of yellow ointment, cold creams.
Beeswax-based nanoparticles used in topical application protect the skin and
increase hydration.

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