Learning Objectives

After studying this unit student will be able to

• understand the role of chemistry in everyday life

• explain drugs and their classification

• understand the drug action in the body

• describe about the chemicals present in food

• explain the cleansing action of detergents

A medicine is a chemical substance which cures the disease, is safe to use, has negligible toxicity and does not cause addiction. In contrast, a drug is a chemical substance which also cures the disease but is habit forming, causes addiction and has serious side effects.

Chemotherapy - Branch of chemistry which deals with treatment of diseases using suitable chemicals. Classification of Drugs - Drugs can be classified on the basis of various parameter like

a) pharmacological effect

b) drug action

c) chemical structure

d) molecular targets

Drug-Target Interaction -

A drug can target various macromolecules present in the body e.g. enzymes and receptors.

a) Enzymes as Drug Targets

i) Enzymes perform two major functions; first, they hold the substrate for a chemical reaction through a variety of interactions and, second, they provide functional groups for the chemical reaction.

ii) Drug can inhibit any of the activities of enzymes i.e. they can block the binding site of the enzyme or can inhibit the catalylic activity of the enzyme. Such drugs are called enzyme inhibitors.

To inhibit the attachment of substrate on active site of enzymes, a drug can compete with the substrate known as competitive inhibitors or it can bind to allorteric site which leads to shape change of the active site.

Receptors as Drug Targets -

In this, drug will target the active site of the receptor.

1st, receptor receives the chemical messenger (chemicals) then shape of the receptor changes and message is received. After that, receptor regains structure and chemical messenger leaves the site.

Drug binds to these sites.

Antagonists - Drug that binds to the receptor site and inhibits its natural function.

Agonists - Drug that mimic the natural messenger by switching on the receptor.

Therapeutic Action of different classes of Drugs:

Antacids: Substances which neutralize the excess hydrochloric acid and raise the $\mathrm{pH}$ to an appropriate level in stomach are called antacids. The most commonly used antacids are weak bases such as sodium bicarbonate, magnesium hydroxide, magnesium carbonate, magnesium trisilicate, aluminium hydroxide gel and aluminium phosphate. These antacids control only the symptoms and not the cause. Since histamine stimulates the secretion of pepsin and $\mathrm{HCl}$, therefore, some antihistamines which prevent the interaction of histamine with the receptors present in the stomach wall are used as antacids. For examples, cimetidine or ranitidine.

Antihistamines: Release of histamine in the body causes allergy. Drugs which interfere with the natural action of histamine by competing with histamine for binding site of receptor where histamine exerts its effect are called antihistamines or anti-allergy drugs. These are widely used for treatment of common cold, conjuctivities, itching of eyes, motion sickness, nausea in pregnancy and post operative vomiting. Some important antihistamine drugs are brompheniramine, terfenadine, diphenylhydramine (benadryl), pheniramine, cetrizine.

Note: Antiallergic and antacid drugs work on different receptors.

Neurologically Active Drugs -

These drugs affect the message transfer mechanism from nerve to receptor.

two types - a) Tranquilizers and b) Analgesics

a) Tranquilizers (psychotherapeutic drugs): These are used for treatment of stress, mild and severe mental diseases. They are essential components of all sleeping pills.

• Hypnotic : Sleep producing e.g. derivatives of barbituric acid (barbiturates) viz., veronal, amytal, luminal and seconal.

• Non-hypnotic e.g. equanil, valium etc.

• Antidepressants e.g. Iproniazid and phenelzine.

b) Analgesics - These are used to reduce pain.

Non narcotic analgesics - Drugs which reduce or abolish pain without causing impairment of consciousness. They do not cause addiction eg. ibuprofen, naproxen, aspirin.

Narcotic analgesics - They are used for relief of post-operative pain, cardiac pain and for pain during child birth. They are habit forming. eg. Morphine, codeine, heroin.

Antimicrobials : These drugs tend to destroy/prevent development or inhibit the pathogenic action of microbes such as bacteria (antibacterial drugs), fungi (antifungal drugs) and virus (antiviral agents).

Antibiotics, antiseptics and disinfectants are antimicrobial drugs.

Antibiotics: are used to treat infections because of their low toxicity for humans and animals.

Types of antibiotics:

These are of two types:

$\quad$i) Bactericidal antibiotics kill the microorganisms. For example. penicillin, streptomycin and ofloxacin

$\quad$ii) Bacteriostatic antibiotics either inhibit or arrest the growth of microorganisms. For example, erythromycin, tetracycline, chloramphenicol (Chloromycetin).

Broad spectrum antibiotics - They are effective against several different types of harmful bacteria. eg. tetracycline, chloramphenicol.

Narrow spectrum antibiotics- They are effective against diseases caused by cocci and some gram positive bacteria or gram negative bacteria eg. penicillin.

Antiseptics and disinfectants: These are used to prevent the growth of microorganisms or to kill them.

Antiseptics are the chemical substances (e.g. antibacterial) which prevent the growth of microorganisms and may even kill them. They are safe to be applied to living tissues. Thus, they are generally applied on the wounds, cuts, ulcers and diseased skin surfaces in form of antiseptic creams like furacin, soframycin. Antiseptics are also added to face powders, breath purifiers, etc. to reduce the odour produced as a result of bacterial decomposition of organic matter on the body or in the mouth.

Disinfectants are chemical substances (i.e. antibacterial) which kill micro-organisms but are not safe to be applied to the living tissues. These are generally used to kill the micro-organisms present in the drains, toilets, floors, etc.

The same substance can act as an antiseptic as well as a disinfectant depending upon the concentration of the solution used. For example, $0.2 \%$ solution of phenol acts as antiseptic whereas $1 \%$ solution acts as disinfectant.

• Dettol is an antiseptic-lt is a mixture of chloroxylenol and $\alpha$-terpineol.

• Bithional is another well known antiseptic which is added to good quality soaps to reduce the odours produced by baterial decomposition of organic matter on the skin.

• Iodine is a powerful antiseptic. It is used as tincture of iodine (which is $2-3 \%$ solution of iodine in alcohol and water). It is applied on wounds.

• Iodoform $\left(\mathrm{CHI} _{3}\right)$ which produces iodine on coming in contact with skin and is used as antiseptic for wounds.

Anti fertility drugs:

These are birth control pills or oral contraceptives. These control the female menstrual cycle and ovulation. Birth control pills contain a mixture of norethindrone (progesterone derivative) and novestrol (estrogen derivative)

Sulpha Drugs:

A group of drugs which are derivatives of sulphanilamide are called sulpha drugs. These have fairly good antibacterial powers and have been widely used against diseases (such as diptheria, dysentery, tuberculosis, etc.) caused by cocci infections, streptococci, gonococci and pneumococci. However, in the recent past, their use has sharply declined due to the availability of more effective and less toxic antibiotics.

i) Sulphadiazine: It is the most widely used sulpha drug and is mainly used for dysentery, urinary and respiratory infections.

ii) Sulphapyridine: It is specifically used for the treatment of pneumonia.

Chemicals in Food or Food Additives:

These are added to food to improve its keeping qualities, appearance, taste, odour and food value.

• Main categories of food additives are:

1. Food colours; flavours and sweeteners; fat emulsifiers and stabilising agents; flour improvers-antistaling agents and bleaches; Antioxidants; Preservatives and nutritional supplements (vitamins, minerals and amino acids).

2. Artifical sweetening agents

i) Saccharine: It is about 550 times sweeter than sugar on mass to mass basis. It is not biodegradable (or is not metabolized in the body) and does not have any calorific value of food. It is excreted as such in urine. It is primarily used as a sweetening agent by diabetic patients.

ii) Aspartame: It is about 100 times as sweet as sucrose. It decomposes at baking or cooking temperature and hence can only be used in cold foods and soft drinks.

iii) Alitame is more table than aspartame. It is about 2000 times as sweet as sucrose.

iv) Sucralose is trichloro derivative of sucrose. It tastes like sucrose and is stable at baking or cooking temperatures. It is about 600 times sweeter than sucrose. It neither provides calories nor causes tooth decay.

3. Preservaties

These are used to protect food against bacteria, yeast and moulds. They are classified into two groups class, I and class II.

Class I preservatives - It includes table salt, sugar and vegetable oils.

Class II preservatives - It includes some chemicals

Sodium benzoate - It is used in soft drinks and acidic foods.

Sodium metabisulphite $\left(\mathrm{Na} _{2} \mathrm{~S} _{2} \mathrm{O} _{5}\right)$ - It is used as preservative for jams, squashes and pickles.

Antioxidants - Chemicals used to prevent oxidation of fats in processed foods such as potato chips, biscuits, breakfast cereals, crackers, etc. are called antioxidants. For example, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). These phenolic compounds are added to preserve fats in packaged food. Oxygen reacts preferentially with BHA or BHT rather than oxidising fats or oils thereby protecting them from spoilage.

Cleansing Agents/Detergents :

Soaps and synthetic detergents.

Chemical substances which concentrate at the surface of the solution or interfaces, form surface films, reduce surface tension of the solution and help in removing dirt and dust by emulsifying grease are called surface active agents or surfactants. The molecule of a surfactant contains two characterstic groups; one of which is water soluble (hydrophilic) and the other is oil soluble (Iyophilic or lipophilic). These are of two types:

1. Soaps

2. Synthetic detergents.

Soaps are sodium or potassium salts of higher fatty acids such as lauric acid $\left(\mathrm{C} _{11} \mathrm{H} _{23} \mathrm{COOH}\right)$, palmitic acid $\left(\mathrm{C} _{15} \mathrm{H} _{31} \mathrm{COOH}\right)$, stearic acid $\left(\mathrm{C} _{17} \mathrm{H} _{35} \mathrm{COOH}\right)$, oleic acid $\left(\mathrm{C} _{17} \mathrm{H} _{33} \mathrm{COOH}\right)$ or linoleic acid $\left(\mathrm{C} _{17} \mathrm{H} _{31} \mathrm{COOH}\right)$.

Soaps are formed by heating fat or oil (i.e., glyceryl esters of fatty acids) with aqueous sodium hydroxide solution. This reaction is called saponification.

Types of Soaps: By using different raw materials, different types of soaps are made. Some examples of different types of soaps are toilet soaps, transparent soaps, medicated soaps, shaving soaps, laundry soaps and floating soaps.

Advantages and Disadvantages of using Soap as Cleansing Agent

Soap is a good cleansing agent and is $100 \%$ biodegradable, i.e, micro-organisms present in sewage water can completely oxidise soap to $\mathrm{CO} _{2}$. As a result, it does not create any pollution problems. However, soaps have two disadvantages:

i) Soaps cannot be used in hard water since calcium and magnesium ions present in hard water produce curdy white precipitates of calcium and magnesium salts of fatty acids. For example,

$$ \underset{\substack{\text { Soluble sodium } \\ \text { stearate } \\ \text { (Soap) }}}{2 \mathrm{C} _{17} \mathrm{H} _{33} \mathrm{COONa}}+\underset{\substack{\text { Calcium chloride } \\ \text { (in hard water) }}}{\mathrm{CaCl_2}} \longrightarrow \underset{\substack{\text { Insoluble } \\ \text { calcium stearate } \\ \text { (scum) }}}{\left(\mathrm{C} _{17} \mathrm{H} _{35} \mathrm{COO}\right) _{2} \mathrm{Ca}}+\mathrm{NaCl} $$

$$ \underset{\substack{\text { Soluble sodium } \\ \text { stearate } \\ \text { (Soap) }}}{2 \mathrm{C} _{17} \mathrm{H} _{33} \mathrm{COONa}}+\underset{\substack{\text { Magnesium sulphate } \\ \text { (in hard water) }}}{\mathrm{MgSO} _{4}} \longrightarrow \underset{\substack{\text { magnesium stearate } \\ \text { (scum) }}}{\left(\mathrm{C} _{17} \mathrm{H} _{35} \mathrm{COO}\right) _{2} \mathrm{Mg}}+\mathrm{Na} _{2} \mathrm{SO} _{4} $$

These insoluble soaps get precipitated as scum and hence a part of soap is wasted. In fact, this scum creates hindrance to good washing because it adheres to fibres of the cloth as gummy mass. Likewise hair washed with hard water looks dull due to this sticky scum. Similarly, due to this gummy mass, dye does not absorb evenly on cloth washed with soap using hard water.

ii) Soaps cannot be used in acidic solutions since acids (present in the solution) precipitate the insoluble free fatty acids which adhere to the fabrics and thus reduce the ability of soaps to remove oil and grease from fabrics.

Synthetic Detergents:

Synthetic Detergents are sodium or potassium salts of sulphonic acids. Unlike soaps, detergents can be used in hard water because the calcium and magnesium salts like their sodium or potassium salts are also soluble in water. However, detergents have one disadvantage. Unlike soaps, they are not completely biodegradable and hence cause water pollution. Detergents are of the following four types

a) Anionic detergents:

These are of the following two types:

i) Alkylhydrogen sulphates: These are obtained from long chain alcohols by treatment with conc. $\mathrm{H} _{2} \mathrm{SO} _{4}$ followed by neutralization with $\mathrm{NaOH}$. For example, sodium lauryl sulphate or sodium stearyl sulphate. These are $100 \%$ biodegradable.

$$ \underset{\substack{\text { lauryl alcohol }}}{\mathrm{C} _{11} \mathrm{H} _{23} \mathrm{CH} _{2} \mathrm{OH}} \xrightarrow[\substack{\mathrm{H} _{2} \mathrm{SO} _{4}}]{\text { Conc. }} \underset{\substack{\text { Lauryl hydrogen sulphate }}}{\mathrm{C} _{11} \mathrm{H} _{23} \mathrm{CH} _{2} \mathrm{OSO} _{3} \mathrm{H}} \xrightarrow{\text { NaOH }} \underset{\substack{\text { Sodium lauryl sulphate }}}{\mathrm{C} _{11} \mathrm{H} _{23} \mathrm{CH} _{2} \mathrm{OSO} _{3}{ }^{-\mathrm{Na}^{+}}} $$

These sodium alkyl sulphates are $100 \%$ biodegradable.

ii) Alkylbenzene sulphonates: These are obtained by Friedel Crafts alkylation of benzene with a long chain alkene or an alcohol followed by sulphonation and neutralization with $\mathrm{NaOH}$. The most commonly used domestic detergents is sodium 4-(1-dodecyl) benzenesulphonate, SDS.

In these detergents, anionic part of the molecule is involved in the cleansing action.

These are also used in toothpastes.

b) Cationic Detergents:

These are quarternary ammonium salts of amines with acetates, chlorides or bromides as anions. For example, cetyltrimethylammonium bromide. These detergents posses germicidal properties and hence are quite extensively used as germicides. They are also used in hair shampoos and in hair conditioners.

Cetylrimethylammonium bromide

(Cationic detergent used in hair conditioners)

c) Non-ionic detergents:

do not contain any ions. These are actually esters of high molecular mass alcohols obtained either by reaction between polyethylene glycol and stearic acid, (e.g., polyethylene glycol stearate) or by reacting long chain alcohols such as lauryl alcohol with excess of ethylene oxide in presence of a base (e.g., lauryl alcohol ethoxylate). Liquid dishwashig detergents contain non-ionic detergents.

d) Zwitteionic detergents:

contain both anionic and cationic parts. They are generally used to protect the native state of proteins during research work.

Disadvantages of detergents: Detergents having highly branched hydrocarbon chains are not biodegradable and hence cause water pollution in rivers. Therefore, to minimize pollution, in most of the detergents used these days, branching is kept to a minimum so that the detergents become easily biodegradable.

PRACTICE QUESTIONS

Question 1- Which of the following is employed as antihistamine?

a) Omeprazole

b) Chloromphenicol

c) Diphenylhydramine

d) Nonrethindrone

Question 2- Aspirin is

a) acetylsalicylic acid

b) benzoyl salicylic acid

c) chlorobenzoic acid

d) anthranilic acid

Question 3- The carboxyl functional group $(-\mathrm{COOH})$ is present in

a) Picric acid

b) Barbituric acid

c) Ascorbic acid

d) Aspirin

Question 4- Barbituric acid is used as

a) An antipyretic

b) An antiseptic

c) An antibiotic

d) A tranquillizer

Question 5- Which among the following is not an antibiotic?

a) Penicillin

b) Oxytocin

c) Erythromycin

d) Tetracycline

Question 6- Antiseptics and disinfectants either kill or prevent growth of microorganisms. Identify which of the following statements is not true.

a) Dilute solutions of boric acid and hyrogen peroxide are strong antiseptics.

b) Disinfectants harm the living tissues

c) A $0.2 \%$ solution of phenol is an antiseptic while $1 \%$ solution acts as a disinfectant

d) Chlorine and iodine are used as strong disinfectants

Question 7- Tincture of iodine is

a) aqueous solution of $\mathrm{I} _{2}$

b) solution of $\mathrm{I} _{2}$ in aqueous $\mathrm{KI}$

c) alcoholic solution of $\mathrm{I} _{2}$

d) aqueous solution of $\mathrm{KI}$

Question 8- The sweetest artificial sugar among the following is

a) aspartame

b) surcralose

c) alitame

d) sucrose

Question 9- The artifical sweetner containing chlorine that has the appearance and taste as that of sugar and is stable at cooking temperature is

a) Aspartame

b) Saccharin

c) Sucrolose

d) Alitame

Question 10- The organic detergent that is used in hair conditioners is

a) sodium dodecylbenzene sulphonate

b) sodium lauryl sulphate

c) tetramethylammonium chloride

d) cetyltrimethylammonium bromide

Question 11- Which one of the folowing is employed as a tranquilizer drug?

a) Promethazine

b) Valium

c) Naproxen

d) Mifepristone

Question 12- Arsenic containing medicine used for treatment of syphilis, is

a) Tetracycline

b) Ofloxacin

c) Erythromycin

d) Salvarsan

Question 13- The class of drugs used for the treatment of stress is

a) Analgesics

b) Antiseptic

c) Antihistamine

d) Tranquilizers

Question 14- Which one of the following is employed as a tranquilizer?

a) Naproxen

b) Tetracycline

c) Chlorpheniramine

d) Equanil

Question 15- The role of phosphate in detergent powder is to

a) Control pH level of the detergent water mixture

b) Remove $\mathrm{Ca}^{2+}$ and $\mathrm{Mg}^{2+}$ ions from the water that causes the hardness of water

c) Provide whiteness to the fabrics

d) Form solid detergent as phorphate-less detergent are liquid in nature

Question 16- The oxidant which is used as an antiseptic is

a) $\mathrm{KBrO} _{3}$

b) $\mathrm{KMnO} _{4}$

c) $\mathrm{CrO} _{3}$

d) $\mathrm{KNO} _{3}$

Question 17- Bithional is generally added to the soaps as an additive to function as a/an

a) Softener

b) Dryer

c) Buffering agent

d) Antiseptic

Question 18- Which of the following is used as a “morning after pill”?

a) Mifepristone

b) Ethynylestradial

c) Norethindrone

d) Promethazine

Question 19- 2-Acetoxy benzoic acid is used as

a) Antiseptic

b) Antidepressant

c) Antimalarial

d) Antipyretic

Question 20- Which of the following is an anionic detergent?

a) Sodium lauryl sulphate

b) Cetyltrimethyl ammonium bromide

c) Glyceryl oleate

d) Sodium stearate

Question 21- Butylated hyroxy toluene as a food additive acts as

a) antioxidant

b) flavouring agent

c) colouring agent

d) emulsifier

Question 22- Which of the following is an analgesic?

a) Ofloxacin

b) Pencillin

c) Aminoglycosides

d) Paracetamol

Question 23- Artifical sweetener which is stable under cold conditions only is

a) Saccharine

b) Sucralose

c) Aspartame

d) Alitame

Question 24- Which one of the following enhances leathering property of soap?

a) Sodium rosinate

b) Sodium carbonate

c) Sodium stearate

d) Trisodium phosphate

Question 25- Which one of the following compounds is added to soap to impart antiseptic properties?

a) Sodium lauryl sulphate

b) sodium dodecyl benzenesulfonate

c) rosin

d) bithional

Question 26- Butylated hyroxy anisole is

a) an antioxidant

b) cleansing agent

c) disinfectant

d) an antihistamine

Question 27- Substance which are used to bring down the temperature in high fever condition are called

a) Antiseptics

b) Pyretics

c) Antibiotics

d) Antipyretics

Question 28- Which among the following detergents is non-ionic in character?

a) Sodium lauryl sulphate

b) Penta erythrityl stearate

c) Cetyltrimethyl ammonium chloride

d) Sodium n-dodecyl benzene sulphonate

Question 29- Which one of the following is not a target molecule for drug function in body?

a) Vitamins

b) Carbohydrates

c) Lipids

d) Proteins

Question 30- Dettol, which is used as a common antiseptic is a mixutre of

a) Chloroxylenol $\&$ Terpineol

b) Terpineol $\&$ Bithional

c) Bithional $\&$ Chloroxylenol

d) Terpineol $\&$ Chlorine

Concept - Map