Classification of Drugs

Chemical classification of drugsChemical constituents Drugs

1. Carbohydrates

a) Monosaccharidase

b) Disaccharide

c) Polysaccharide

Gum

Mucilages

Cellulose

- Dextrose, fructose, galactose

- Sucrose, Lactose, Maltose

- Starch

- Acacia, Tragacanth

- Plantago seed

- Cotton

2. Glycosides

a) Cardiac

b) Anthraquinone

c) Saponins

d) Cyanophore

- Digitalis, strophanthus

- Aloe, Cascara, senna

- Arjuna

- Wild cherry bark

3. Tanins Amla, Bohera, Ashoka bark

4. Volatile oil Clove oil, rose oil, peppermint oil, tulsi etc

5. Lipids

a) Fixed oils & fats

b) Waxes

- Olive oil, castor oil, coconut oil etc

- Bees wax

Carbohydrates are aldehyde or ketone derivatives of higher polyhydric alcohol.

It is a neutral compound made up of Carbon, hydrogen and oxygen (C, H, O) in which H and O are in generally the same ratio as in water (H2O)

General formula of carbohydrate is – (CH2O)n.

The Chlorophil of the plants can easily synthesize carbohydrates from air, CO2 and H2O in the presence of light. The reaction is as follows –

CO2 + H2O Carbohydrate + O2

Carbohydrates

Carbohydrates

Nutrient – good source of energy

Sweetening agent – Tablet, syrup, suspension

Masking bad test – tablet, liquid (iron syrup)

Diluent, binder, disintegrating agent, suspending agent, demulcent.

Antibacterial agent (at 66.6%) and preservative

Antioxidant (it is a reducing sugar)

Uses of Carbohydrates

By considering sweet taste-imparting property CHO are classified as-

1. Sugar: Monosaccharides – glucose, fructose, galactose.

Disaccharides - Sucrose, lactose, maltose.

2. Nonsugar: Polysaccharides – starch, inulin, gums and mucilage, cellulose.

Carbohydrates - Classification

Carbohydrates

Sugar Nonsugar (Polysaccharide)

Monosaccharides Disaccharides

Glucose Fructose Galactose

Sucrose Lactose Maltose

Starch Cellulose Inulin Gums &mucilage

Monosaccharides, the simplest CHO, are aldehydes or ketones that have multiple hydroxyl groups. The general formula of many is (CH2O)n.

It is obtained from hydrolysis of starch.

In nature it is found in grapes and fruits.

Glucose (Monosaccharides)

Structure CH=O | HC-OH | HO-CH | HC-OH | HC-OH | CH2-OH

D-Glucose

Ring Structure of Glucose

Nutrient – oral or intravenous injections.

It is also used in anticoagulant solution to preserve whole blood.

For manufacture of beverage, ice-cream, bakery products and in the caning industry.

Glucose - Use

Liquid glucose

It is obtained from incomplete hydrolysis of starch. It is serupy liquid consist chiefly of dextrose, with maltose and water. It is used as a sweetening agent as a substitute of sucrose in syrup and as a tablet binder and coating agents.

Fructose is a ketone sugar occurs naturally in most sweet fruits and honey.

Use:

1. Nutrient – food for diabetics and may be of particular benefit of diabetic acidosis.

2. Infant formula.

3. When given parenterally it produces less urinary secretion than glucose.

Fructose

Structure of Fructose

Ring structure of fructose

Glucose & fructoseGlucose & fructose

6-membered ring structure

5-membered ring structure

Disaccharide consists of 2 monosaccharides (glucose & fructose) joined by an glycosidic bond.

Sucrose is the only disaccharide abundant in the free state in plants.

It occurs in fruit juice , sugar cane, sugar beet and in many other plants.

Commercially it is obtained from sugar cane and sugar beet.

Sugar (Sucrose, disaccharides)

Structure

glucose Fructose

Sugar (Sucrose, disaccharides)

glycosidic bond

OH H

H

OHH

OH

CH2OH

HOH H

H

OHH

OH

CH2OH

H1

3

14

223

4

6

5

6

5

-linkage

O OO

n

Nutrient – good source of energy

Sweetening agent – Tablet, syrup, suspension

Masking bad test – tablet, liquid (iron syrup)

Antibacterial agent (at 66.6%) and preservative

Antioxidant (it is a reducing sugar)

Uses of Sugar

The saccharides which reduce Fehling’s reagent and Tollen’s

reagent are called reducing sugar.

For example: all monosaccharides (glucose, fructose, lactose).

Reducing sugar

The saccharides which do not reduce Fehling’s

reagent and Tollen’s reagent are called non-reducing

sugar.

For example: disaccharide (sucrose) and

polysaccharide.

Non-reducing sugar

It is a reducing sugar. Upon hydrolysis lactose yields d-

glucose and d-galactose. It is obtained from fresh,

unpasturized or pasturized cow’s milk. It is also known

as milk sugar. The sugar is crystallized from the whey

obtained in cheese manufacture. The manufacturing

scheme is shown below –

Lactose

Milk Keep stand for few hour Separation

of cream (Skimmed milk) Treated with rennin

Cheese Separation of liquid (Whey)

Crystallization of Lactose Redissolved in water

Decolorized with Charcoal Recrystallized

Lactose

Uses: Diluent – TabletNutrient – Infant food

Caramel or Burn Sugar:

It is a concentrated solution of the product obtained by

heating sugar or glucose until the sweet taste is destroyed and

a uniform dark brown mass result. A small amount of alkali,

added during heating of the sugar.

Uses:Coloring agent – Food and Pharmaceuticals

• It is originally obtained from the ripe berries, Sorbus sp.

(Fam – Rosaceae). • It also occurs in many fruits but is generally prepared

from glucose by hydrogenation or by electric reduction.

Uses:• Humectants: (act as moisturizers by attracting water.

They are often used to prevent creams from drying out). • Sweetner• Diluent/Vehicle• Food – Diabetic food (substitute of glucose)• Diuretic

D-Sorbitol:D-Sorbitol:

Polysaccharide

The complex CHOs are generally called polysaccharide as they are formed by the linkage of a large number of monsaccharide units.

The polysaccharides yield the component monosaccharide units on enzymetic or acid hydrolysis.

Starch

starch is most widely distributed organic compound in plants.

It is produced in large quantities in green leaves as the temporary storage form of potosynthetic products.

It stored in seed, stems and roots. It is lacking in animal.

Commercially it is obtained from corn, cereal (rice, wheat, maize), potato tubers etc.

Polysaccharide - Starch

Starch generally is a mixture of two structurally different polysaccharides which are –

Amylose (-amylose):It is a linear molecule composed of 250 – 300 d-glucose units uniformly linked by -1,4 glucosidic bond.

Starch - Chemistry

Amylopectin (a-amylose):It consists of 1000 or more d-glucose units of which most are connected with -1,4 linkage but there are also a number of -1,6 linkage occurring (4%) at branch points.

Structure of Amylopectin

Structure of amylose:

Amylose vs Amylopectin

Property Amylose Amylopectin

Water solubility More soluble Less soluble

Reaction with I2 Blue color complex purple color

Composition 25% of total starch 75% of total starch

Unit composition D-glucose D-glucose

Type of linkage -1,4 glucosidic bond -1,4 & -1,6 glucosidic bond

Shape of the molecule Linear Branched

Enzymetic hydrolysis -amylase, Split -1,4 -amylase, Split -1,4 & -1,6

Acid hydrolysis (HCl or H2SO4)

D-glucose D-glucose

Diluent

Binder

Disintegrating agent

Uses of Starch

Cellulose is the main structural material of

trees and other plants.

Wood is 50% cellulose, while cotton wood is

almost pure cellulose.

The general formula of cellulose is:

(C6H10O5)n.

Cellulose

Chemical structure:

Cellulose is made of about 5,000 glucose units joined

to each other by -1,4-glycosidic bonds.

Properties:

It decomposes on strong heating.

It is insoluble in water and most organic solvent.

It is hydrolysed by heating with dilute HCl or H2SO4, give d-glucose.

Cellulose

Methyl cellulose

Ethyl cellulose

Hydroxyethyl cellulose

Hydroxypropyl methylcellulose

Sodium carboxymethyl cellulose (Na-CMC)

Derivatives of Cellulose

Derivatives of Cellulose

Methyl celluloseMethyl cellulose

It is a methyl ether of cellulose containing not less than 26% and not more than 33% of methoxy (-OCH3) groups.

Preparation:

It is obtained by reaction of cellulose with caustic soda (NaOH) and an organic solvent (CH3Cl).

Properties:

It swells in water to produce a clear viscous solution.

Use:Suspending agent –suspension dosage form.Binder- tablet dosage form

Derivatives of Cellulose

Ethyl cellulose

It is an ethyl ether of cellulose containing not less than 45% and not more than 50% of ethoxy (-OC2H5) groups.

Use:• Suspending agent –suspension dosage form.• Binder- tablet dosage form

Derivatives of Cellulose

Hydroxyethyl cellulose

• It is modified cellulose in which the H of –OH groups

is substituted by hydroxyethyl (-OC2H5) groups.

• It is soluble in water.

Use:• Suspending agent –suspension dosage form.• Binder- tablet dosage form• Thickener

Derivatives of Cellulose

Sodium Carboxymethyl cellulose (CMC)

• It is the sodium salt of polycarboxymethyl cellulose in which the H of –OH groups is substituted by

carboxymethyl (-OCH2COOH) groups.

Use:

• Suspending agent –suspension dosage form.

• Binder- tablet dosage form

• Thickener

Gums & Mucilages• Both gums and mucilages are generally considered as

decomposition products of cellulose. They are translucent, amorphous substances usually produced by plants as a protective after injury.

• Gums when hydrolysed, yield large proportion of sugars and also contain a complex organic acid nucleus, by means of which they form salt with calcium, magnesium, etc.

• Gums are precipitated from solution by alcohol and lead acetate solution.

• Gums readily dissolve in water.

• Mucilages are generally sulfuric acid esters, the ester group being a complex polysaccharide.

• Mucilages do not dissolve in water but form slimy masses.

Sources of Natural Gum and Mucilage

1. Acacia:

2. Tragacanth

3. Agar:

Acacia

It is the dried gummy exudate from the stems and

branches of Acacia senegal (Fam. Leguminosae). It

is commonly known as gum Arabic.

Uses:

• Suspending agent• Demulcent• Granulating agent• Binder

Tragacanth

Source: • It is gummy exudate from Astragalus gummifer (Fam

– Leguminosae). • It is commonly known as Gum Trgacanth.

Uses: • Suspending agent• Emollient• Binder

Agar

Source: It is the dried, hydrophilic polysaccharide complex

extracted from the algae known as Gelidium cartilagineum

(Fam – Gelidiaceae); Gracilaria cofervoides and other

species.

Uses: •Suspending agent•Thickening agent•Laxative•Bacterial media

Tests for Carbohydrates

1. Fehling’s test

2. Molisch’s test

3. Osazone formation

4. Resorcinol test

5. Test of pentoses

10% solution of a-naphthol in alcohol is known as Molisch’s reagent

Tests for Carbohydrates

1. Molisch test:

A solution of CHO is prepared with -napthol and taken in test tube.

Concentrated sulphuric acid is added along the side of test tube

This test is standard test for identification of CHO.

A purple ring is formed on the junction below the aqueous layer which indicates the presence of CHO. [With insoluble CHO eg. Cellulose, the color will produce on shaking the reaction mixture].

Tests for Carbohydrates

1. Molisch test:

a negative test (left) and a positive test (right)

Fehling’s solution is an alkaline solution of cupric ion complex with tartrate ion.

Tests for Carbohydrates

1. Fehling’s solution test:

To a heated solution of the CHO containing substance add drop by drop a Fehling’s solution (equal parts of Fehling’s solution 1 & 2).

Red precipitate of cuprous oxide is produced

This test is used for reducing sugar such as all monsaccharides and many disaccharides like lactose, maltose. For nonreducing sugar like disaccharide (sucrose) and polysaccharides boils with acid for hydrolysis before testing with Fehling’s solution, or cuprous oxide will fail to precipitate.

The cupric ion (complexed with tartrate ion) is reduced to cuprous ion by the aldehyde (which is oxidized) and precipitates as cuprous oxide (Cu2O); for this reason, sugars that react with Fehling's solution are called reducing sugars.

Fehling’s solution test:Fehling I consists of 7 g of hydrated copper(II) sulfate dissolved in 100 mL of dist. water. Fehling II is made by dissolving 35 g of potassium sodium tartrate and 10 g of sodium hydroxide in 100 mL of dist. water Fehling's reagent: Equal volumes of Fehling I and Fehling II are mixed to form a deep blue

solution.

conical measure 1 glucose solution brick red precipitate

conical measure 2 fructose solution brick red precipitate

conical measure 3 sucrose solution no change