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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5322_Библиотеки_им_академика_М_И_Перельмана.pdf
138 Textbook of Pharmacognosy
4. True or False Statements:
1. Agar contains nitrogen containing substance. [True/False]
2. Pectin can be used as a plasma substitute. [True/False]
3. Guar gum is located in the endosperm of seeds. [True/False]
4. Agarose is the water insoluble portion of agar. [True/False]
5. Monosaccharides cannot be further hydrolysed. [True/False]
6. The monosaccharides in oligosaccharide are joined together by
glycosidic linkages. [True/False]
7. Polysaccharides have no taste and are insoluble in water.
[True/False]
8. Gum Arabic is highly soluble in glycerol. [True/False]
9. Agar powder is not soluble in boiling water. [True/False]
10. Agaropectin determines the viscosity of agar solution.
[True/False]
5. A. Match the following:
1. Cod liver oil [ ] a. Suppositories
2. Olive oil [ ] b. Vitamin A
3. Linseed oil [ ] c. High iodine value
4. Shark liver oil [ ] d. Used for eczema and psoriasis
5. Kokum butter [ ] e. Vitamins A and D
B. Match the following:
1. Dextrin [ ] a. Braconnot
2. Pectin [ ] b. Biot and Persoz
3. Waxy starch [ ] c. Payen and L’ersoz
4. Mel depuratum [ ] d. Potato starch
5. Diastase [ ] e. Clarified honey
7
Systematic
Pharmacognostic
Study of Lipids
LIPIDS
Lipids have a wider distribution in vegetable and animal kingdom and in
plants they occur abundantly in fruits and seeds. In animals, lipids of a
complex nature occur in brain and liver and play a significant role in the
structure of cell membranes. Lipids are esters of long-chained fatty acids
and alcohols. These are sparingly soluble in water but dissolve in organic
solvents like chloroform, methanol, ether, benzene, hot alcohol and
petroleum ether, the first two being the universal lipid solvents. They yield
fatty acids on hydrolysis which can be readily utilised.
Lipids are normally grouped under three headings, simple lipids,
compound lipids and derived lipids.
Simple Lipids
A simple lipid is a fatty acid ester of different alcohols and it carries no other
substance. These belong to a heterogeneous class of nonpolar compounds,
mostly insoluble in water, but soluble in nonpolar organic solvents
(chloroform and benzene). These are esters of fatty acids with various
alcohols. Simple lipids are represented by neutral fats, fats and oils and waxes.
Neutral Fats
Neutral fats are the esters of fatty acids with glycerol. These are also called
triglycerides as three molecules of fatty acid undergo condensation
with a single molecule of glycerol to form fat (tributyrin). Neutral fats are
Tributyrin (C15H26O6)
Linear formula (CH
3CH2CH2
COOCH2)2CHOCOCH2CH2CH
139
3
140 Textbook of Pharmacognosy
composed of mixed glycerides (triglycerides which on hydrolysis yield
non-identical fatty acids) which do not possess any free acid or basic group.
Fats and Oils
The fats are esters of fatty acids with glycerol. The fats are also called
triglycerides because all the 3-hydroxyl groups of glycerol are esterified.
Fats are tasteless, odourless, colourless and neutral in their reaction. They
are liquids or solids or semisolids lighter than water and immiscible with
water. The fats are insoluble in water, but readily soluble in ether,
chloroform, petroleum ether, benzene and carbon tetrachloride. They are
readily soluble in hot alcohol but slightly soluble in cold alcohol. They are
themselves good solvents for other fats, fatty acids, etc. Several neutral
fats are readily crystallised (beef and mutton). They have lower melting
points. The specific gravity of the solid fats is about 0.86. They spread
uniformly over the surface of water (due to lower surface tension).
Though they are nonvolatile, they decompose on strong heating and
readily form emulsions when they are agitated with water in presence of
emulsifiers like soap and gelatin. The vegetable fats contain phytosterol
while the animal fats contain cholesterol. They have a larger amount of
saturated fatty acids and undergo melting at higher temperatures (e.g.
Lard). The saturated fatty acids possess higher melting point and are solids
at room temperature. They have a maximum number of attached hydrogens
and one terminal carbon has 3-hydrogen while the other end has a
carboxylic group attached to it. They occur in a large proportion in animal
triglycerides like palmitic acid and stearic acid. The fats are found in nature
in large quantities, and are the best reserve of the food material in the
human body. They act as insulator for the loss of body heat. They also act
as a padding material for protecting the internal organs.
The oils are fats in the liquid state. The oils (fixed oils) contain a high
proportion of unsaturated fatty acids, melt at a lower temperature and are
liquids at room temperature. (e.g. coconut oil, olive oil and cotton seed
oil). But, at lower temperatures, these may attain the state of a fat and fats
too attain the state of oil at higher temperature. In general, all vegetable
lipids are liquids (oils) at ordinary temperature while those from animals
are fats, except cocoa butter (solid oil) and cod and shark liver oils (liquid
fats). The unsaturated fatty acids have a lower melting point and are liquids
at room temperature. They possess one or more double bonds. They occur
more in plant glycerides such as oleic acid, linoleic acid and linolenic acid.
Oils are grouped into three categories namely, drying oils, nondrying oils
and semidrying oils.
Oleic acid (C18H34O2) or [CH3 (CH2)7CH=CH(CH2)7COOH]
Systematic Pharmacognostic Study of Lipids 141
Stigmasterol or Stigmasterin (Phytosterol) C29H48O
Cholesterol (animal sterol) C27H46O
Palmitic acid (C16H32O2) or [CH3(CH2)14CO2H]
Stearic acid (C18H36O2) or [CH3(CH2)16CO2H]
Linoleic acid (C18H32O2) or [CH3(CH2)4CH=CH–CH2-CH=CH(CH2)7CO2H]
Linolenic acid (C18H30O2) – [H3C(–CH2–CH=CH)3–(CH2)7–COOH]
a. Drying oils: The drying oils possess glycerides of saturated acids with
2 or 3 double bonds like oleostearic acid and linolenic acid. These
142 Textbook of Pharmacognosy
possess a property of slowly absorbing oxygen from air and to
polymerise leading to the formation of a transparent elastic film or
coating within 4–5 hours on the surface. These are useful in the
manufacture of paints and oil cloth (linseed oil and hemp seed oil).
b. Nondrying oils: The nondrying oils possess triolein. They get rancid
due to oxidation on exposure to light and storage during which
process they are decomposed to glycerol and saturated and
unsaturated fatty acids. The former get decomposed to ketones while
the latter get oxidised to aldehydes and acids with a few carbon atoms
(olive oil and almond oil).
Triolein or 1, 2, 3-(9Z-octadecenoyl)-glycerol (C57H
104O6
)
c. Semidrying oils: The semidrying oils have a lower/higher content of
linolenic acid when compared to the drying/nondrying oils. Under
excess hydrogen under pressure they get hydrogenated and if heated
during cooking, some amount of glycerol escapes out due to
hydrolysis and produces acrolein which may cause headache and eye
trouble (sunflower oil and cotton seed oil).
Acrolein (C3H4O) or [CH2=CHCHO]
The fats and oils are used externally as emollients in treating wounds,
burns, sunburn, eczema, dandruff, etc. as they have a protective action
on the skin. Internally they can also be used as mild laxatives (castor
oil). Some oils are used in the treatment of leprosy (chaulmoogra oil).
These can also be used as food supplements, as vehicles and in the
preparation of ointments and liniments. These also find a use in
avitaminosis as some oils contain fat soluble vitamins like A, D and E.
Vitamin A: Retinol (C20H30O)
Systematic Pharmacognostic Study of Lipids 143
Vitamin D: Ergocalciferol or calciferol (C28H44O)
Vitamin E: Tocopherol (C29H50O2)
Waxes
The waxes are solid esters of long-chain fatty acids (palmitic acid) with
aliphatic or alicyclic higher molecular weight monohydric alcohols (other
than glycerol). These are water-insoluble due to the weakly polar nature
of the ester group. Waxes are similar to fats in their physical properties
and are solids, semisolids or occasionally liquids. These are the esters of
fatty acids and alcohols with a high molecular weight. The fatty acids that
occur in waxes are similar to those in fats. The true waxes have alcohols
other than glycerol while steryl esters have sterols. The component fatty
acids and alcohols usually possess 24–36 carbons. The hydrocarbon chains
in the waxes are completely reduced and are insoluble in water and are
highly resistant to atmospheric oxidation. The waxes are chemically inert
and are not digested by the enzymes, but split slowly with hot alcoholic
potassium hydroxide. They are useful in the preparation of furniture polish.
The waxes in insects, birds and furred animals serve as water barriers.
These also help as a protective coating on the leaves and fruits, e.g. beeswax (from bees), spermaceti (from the head of sperm whale), carnuba wax
(from Brazilian palm) and lanolin (from the sheep wool). These are not
suitable as food because the enzymes which can hydrolyze waxes are not
144 Textbook of Pharmacognosy
present in our digestive system. These are mainly of three types, namely:
true waxes—which are the esters of higher fatty acids with acetyl alcohol
or higher straight chain alcohols; cholesterol esters are the esters of fatty
acid with cholesterol; and vitamin A and vitamin D esters are palmitic or
stearic acid esters of retinol (vitamin A) or vitamin D respectively.
Compound Lipids
These are marked by the presence of some additional groups or elements
besides fatty acids and alcohol. The additional groups may have either a
protein or elements like phosphorus, sulphur and nitrogen. The most
important groups of compound lipids are phospholipids and glycolipids.
The most important groups of compound lipids are phospholipids and
glycolipids. Other compound lipids are: Lipoproteins, amino lipids, and
sulpholipids (sulphatides).
Phospholipids (Phosphatides)
The phosphatides are the esters of fatty acids with glycerol containing an
esterified phosphoric acid and a nitrogen base. These are present in larger
amounts in the nerve tissue, brain, liver, kidney, pancreas and heart.
These contain glycerol, phosphoric acid and fatty acids and are fats
in which one of the fatty acids has been replaced by phosphoric acid.
The important phospholipids are lecithin, cephalin, plasmogen,
phosphoinositide and phosphosphingoside. Lecithin in animals is needed
for the normal transport and utilisation of other lipids in the liver. This is
an important component of lipoproteins and occurs in the yolk of the egg.
The enzyme lecithinase is present in bee venom and cobra venom. It
dissolves in ether and alcohol but insoluble in acetone. Upon exposure to
air, it becomes darker in colour. Cephalin occurs in tissues of animals in
association with lecithin and also occurs in soybean oil. In cephalin, choline
is replaced by ethanolamine, colamine or serine. Stearic acid, oleic acid,
linoleic acid and arachidonic acid are the fatty acid components of cephalin.
Plasmogen is present in the seeds of higher plants and abundant in the
brain and muscles of animals. The molecular structure is similar to lecithin
or cephalin except that a complex aldehyde is attached to the alpha-carbon
of glycerol. This dissolves in all types of lipids. Phosphoinositide is widely
distributed in plants as monophosphoinositide and is also reported to be
in brain tissues as diphosphoinositide. Phosphosphingoside occurs in
nervous tissues and is absent in plants and microbes. Sphingosine or
phosphosphingosine replaces glycerol.
Biologically, these increase the rate of fatty acid oxidation, and act as
the carriers of inorganic ions across the membranes. They help in blood
clotting and also act as prosthetic group to certain enzymes. They also
form the structures of the membranes, matrix of the cell wall, myelin sheath,
microsomes and mitochondria.
Systematic Pharmacognostic Study of Lipids 145
Lecithin (C40H80NO8P) Sphingosine (C18H37NO2)
Cephalin (C41H78NPO8)
Arachidonic acid (C20H32O2)
Phospholipids on the basis of the type of alcohol present, are classified
into three types: Glycerophosphatides (glycerol is the alcohol group, e.g.
cephalin [phosphatidyl ethanolamine]); lecithin [phosphatidyl choline],
phosphatidyl serine, plasmalogens and phosphatidic acid); phosphoinositides (inositol is the alcohol, e.g. lipositol [phosphotidyl inositol];
and phosphosphingosides (sphingosine is an amino alcohol, e.g.
sphingomyelin).
Glycolipids (Glycosphingolipids)
These lipids contain an amino alcohol [sphingosine or iso-sphingosine]
attached with an amide linkage to a fatty acid and glycosidically to a
carbohydrate moiety [like a sugar, amino sugar and sialic acid].
146 Textbook of Pharmacognosy
These are represented by phosphosphingosides associated with
carbohydrates and occur in plant seeds. The common carbohydrate units
are galactose, arabinose and fructose. These are represented by cerebrocides
and ceramides. The former are mainly associated with myelin sheath of
nerves and white matter of the brain while the latter serve as antigens.
These are further classified into: Cerebrosides and Gangliosides. The
former contain galactose, a high molecular weight fatty acid and
sphingosine. These are the chief constituents of myelin sheath. These are
differentiated by the type of fatty acid, e.g. kerasin [with lignoceric acid],
cerebron [with cerebronic acid (hydroxyl-lignoceric acid), nervon (with
an unsaturated homologue of lignoceric acid, called nervonic acid),
oxynervon (with hydroxyl-nervonic acid), etc. The latter are the glycolipids
that occur in the brain. The gangliosides contain ceramide (sphingosine +
fatty acids), glucose, galactose, N-acetylgalactosamine and sialic acid. Some
also contain di-hydrosphingosine (or gangliosine) in place of sphingosine.
Most of these contain glucose, 2 molecules of galactose, 1 molecule of
N-acetylgalactosamine and up to 3 molecules of sialic acid.
Derived Lipids
These are the hydrolytic products of lipids and lipid like compounds such
as sterols, carotenoids, essential oils, aldehydes, ketones, alcohols and
hydrocarbons. These are the solid waxes which occur abundantly as
alcohols or esters of fatty acids and are highly soluble in fat solvents.
These do not get saponified. Sterol distribution is wider in plants,
animals and microbes, and also occurs in cell membranes and cellular
components.
Spinasterol (C29H48O)
Systematic Pharmacognostic Study of Lipids 147
Sitosterol (C29H50O)
The best known sterols are cholesterol (in animals), spinasterol (in spinach),
cabbage stigmasterol (in coconut and soybean) and sitosterol (in the seeds
of cereals). Carotenoids are the important plant pigments and essential
oils can be isolated from pine, peppermint, lemon, eucalyptus and rose.
These include: Fatty acids, saturated fatty acids, and others. Essential fatty
acids, refined and hydrogenated oils, and steroids. Castor oil, cod liver oil,
shark liver oil, linseed oil, cocoa butter, kokum butter, beeswax, wool fat,
hydnocarpus oil, lard oil and olive oil are described below.
CASTOR OIL
Synonyms
Ricinus oil, Oleum ricini, Aceite de Ricino (Colombia), Zejt ir-Riegnu
(Maltese), Zait al kharwaa (Arabic), Erand oil (Tamil-from Sanskrit, Eranda),
Aamudam (Telugu).
Synonyms for Castor
Castor oil plant (English), Erandam or Vatari (Sanskrit), Ricin (French),
Gemeiner Wunderbaum (German), Arand (Hindi and Punjabi), Khirva
(Arabic), Bedanjir (Persian), Bheranda or Sadabheranda (Bengali), Eri
(Assamese), Erandi (Gujarati and Maharashtrian), Aamudamu chettu
(Telugu), Chittamani (Tamil), Haralu (Kannada), Chittamanaku
(Malayalm), Endaru (Sinhalese), Kesusi (Burmese), Miniak-jarah
(Malayese).
Biological Source
Castor oil is a fixed vegetable oil obtained from the seeds (castor beans) of
Ricinus communis L. (Family: Euphorbiaceae). The name Ricinus is a Latin
word for tick and is so named because the seed has red markings (bloody)
and a bump (caruncle) which resembles the head of certain dog-ticks and
communis in Latin means ‘common’. The common name ‘castor oil’ comes