Broadly environment consists of two parts a) physical or abiotic (non-living) components and b) living or biotic components.

Abiotic components of the environment are air, water, soil, energy radiation, etc. Biotic components of the environment are microbes (such as bacteria, algae and fungi), plants, animals, etc.

Environmental chemistry deals with the study of the origin, transport, reactions, effects and fates of chemical species in the environment.

Components of Environment:

Biosphere:

All the parts of the earth are not suitable for survival of organisms. Some parts are too hot or very cold to support life. The part of the earth on which organisms can survive and reproduce is called biosphere. A perfect and delicate balance is needed between the organism and other components of environment for the survival of the organism. A disturbance, damage or abrupt change in the quality of environment poses a threat to the survival and well-being of organisms.

Atmosphere:

The atmosphere is a thin layer of air (a mixture of gases) around the earth which is a great source to all living organisms.

The atmosphere is important for the survival of organisms because this is the layer which consists of free oxygen and water vapour. It also consists of nitrogen which is fixed in the soil in nitrification and used by plants.

Hydrosphere:

Hydrosphere is the part of the earth on which all types of water resources exist, viz., oceans, seas, rivers, lakes, glaciers, ice caps, groundwater, etc. After oxygen water is needed by the organisms for their survival.

Lithosphere:

The lithosphere is the part of the earth where all types of minerals, metals, organic matters, rocks, soils, etc. exist. The soil is part of the lithosphere.

Environmental Pollution:

The word pollution is derived from the Latin word pollutionem which means to soil. The waste generated through human activities and spoiling the natural environment is termed as pollutants. Pollution is defined as the deterioration or unclean objectionable conditions in the quality of natural resources such as air, water and soil because of the action or presence of unwanted substances beyond a certain limit. Thus pollution creates an unwanted effect on our surroundings that have harmful effects on animals, plants and human beings.

Causes of Pollution:

In ancient times civilizations developed along the river banks. The ecosystem was sufficient to cater the needs of those civilizations. But due to the rapid growth of population people were forced to move away from river banks to other places. For creating shelter natural resources such as trees and soil were used. For comfort, humans started manufacturing industries. The industrial waste aggravated the problem of pollution. To cater food requirement of increasing population more food was required. Hence to increase agricultural yield pesticides and chemical fertilizers were manufactured and were used in excess quantity. All these wastes find its way to water sources such as sea, river, lakes and ponds and affected the aquatic organisms. It decreased the supply of potable water.

The causes of pollution can be summarized as follows

• Rapid industrial population growth and urbanization.
• Rapid industrial and technological growth led to the increase in the release of poisonous matter in the air, water and soil. Excessive use of the automobiles is also a major cause.
• The manufacturing of drugs, antibiotics, pesticides, fungicides, herbicides etc. aggravated the pollution problem.
• Excess use of chemical fertilizers and pesticides in agriculture,
• A large release of industrial effluents and emissions from industries, power projects, etc.
• Radioactive waste released from nuclear power plants add tests is hazardous because it shows its effect in future generations.

Pollutants:

Pollutants are defined as the substances or the effect introduced into the environment in significant amounts in solid, semisolid, liquid gas or sub-molecular particle form due to which there is a detrimental (bad) effect on the environment.

General Classification of Pollutants:

• Physical Pollutants: Noise, radiation, unpleasant odours, heat, etc.
• Chemical Pollutants: Harmful gases like CO2, CO, SO2, H2S, S, NO, NO2, hydrocarbons, etc. carbon and dust particles, heavy metals, insecticides, pesticides, herbicides, petroleum products, soli and liquid waste, radioactive substances, etc.
• Biological Pollutants: pollen grains, microorganism, overpopulation

Classification of Pollutants on the Basis of the Origin:

Natural Pollutants:

Fires in forests may be caused by lightning strikes produces a large amount of CO2 which is released into the atmosphere.

Soil erosion due to wind or water flow increases suspended particulate matter and dust in the air. They may enter water bodies due to washing down by rain or natural waterfalls.

Volcanic eruptions add pollutants like SO2 and solid particles in form of ash to the Volatile organic compounds from Leaves, trees and dead decaying organisms give volatile organic compounds which mix the atmosphere.

Natural radioactivity by radioactive substances like uranium, thorium, etc.

Anthropogenic Pollutants:

Pollutants added to the environment through human activities are termed anthropogenic pollutants. They are further classified as primary pollutants and secondary pollutants.

Primary pollutants are those pollutants which are added directly in a harmful form to the atmosphere. eg CO₂ and CO from the burning of fossil fuel; SO₂ and oxides of nitrogen from vehicular combustion, thermal power stations, etc.

Secondary pollutants are the products of the reaction between the primary pollutants and normal environmental constituents.

2SO₂  + O₂ → 2SO₃

In this case SO₂ a primary pollutant, O₂ a normal constituent of air to give secondary pollutant SO3. Further, SO3 reacts with water vapour present in the atmosphere and forms the sulphuric acid (secondary pollutant).

2SO₃  +   H₂O  →  H₂SO₄

Nitric oxide (NO), a primary pollutant reacts with oxygen to give NO2 which is a secondary pollutant.

2NO  + O₂ → 2NO₂

Classification of Pollutants on The Basis of The Type of Source:

Industrial Pollutants:

Paper, textile industries, tanneries and distilleries dispose various effluents like oil, grease, plastic and metallic wastes into
the environment.

Domestic Pollutants:

Detergents, fluoride toothpaste, edible colours, food flavouring agents, polythene bags and wrappers. Crop burnt in the field after harvesting. Methane is produced in cattle stomach and in stagnant paddy fields is also a domestic pollutant.

Classification of Pollutants on The Basis of Their Degradation:

Non-degradable Pollutants:

The substances which do not degrade or degrade very slowly are called non-degradable pollutants. e.g. mercuric salts, lead salts, chromium salts, polythene, long chain phenolic chemicals, pesticides and D.D.T., etc.

These pollutants are not recycled in the ecosystem, hence get accumulated in the environment. Hence their small presence is also dangerous.

Degradable Pollutants:

These substances get degraded into the atmosphere due to the action of microorganisms. e.g. Domestic wastes, sewage, plan leaves and residues.

They are recycled in the ecosystem but their excess accumulation prohibits the complete degradation.

Classification of Pollutants on The Basis of The Motion of Source of Pollution:

Stationary Source Pollutants:

The pollutants released from a fixed location or a well-defined area is known as the stationary source. e.g. smokestacks of power plants, smelters, surface mines, etc.

Mobile Source Pollutants:

The pollutants released from diffused sources or the sources that move from place to place is termed as a mobile source. e.g. automobiles, buses, aircrafts, ships, trains, etc. The various pollutants of water.

Atmospheric Pollution:

On the basis of medium, the pollution is classified as

• Air Pollution
• Water pollution
• Soil pollution

These pollutions we shall study in detail in upcoming articles.

The post Environmental Chemistry appeared first on The Fact Factor.

In the last article, we have studied the use of chemicals in food is in the form of food additives, food preservatives, artificial sweeteners, and antioxidants. In this article, we shall study about cleansing agents: Soap and detergent

Soaps:

Cleansing agents soaps and synthetic detergents improve the cleansing properties of water. These help in the removal of fats that bind other materials to the fabric or skin. They are used for cleaning purposes and are sodium or potassium salts of long-chain fatty acids, e.g., stearic, oleic, and palmitic acids.

Only sodium and potassium soaps are soluble in water and are used for cleaning purposes. Generally, potassium soaps are soft to the skin than sodium soaps. These can be prepared by using potassium hydroxide solution in place of sodium hydroxide.

Soaps containing sodium salts are formed by heating fat (i.e., a glyceryl ester of fatty acid) with aqueous sodium hydroxide solution. This reaction is known as saponification. In this reaction, esters of fatty acids are hydrolyzed and the soap obtained remains in colloidal form. It is precipitated from the solution by adding sodium chloride. The solution left after removing the soap contains glycerol, which can be recovered by fractional distillation.

Types of Soaps and Their Preparations:

Basically, they are made by boiling fats or oils with suitable soluble hydroxide. Variations are made by using different raw materials.

• Toilet soap is prepared by using better grades of fats and oils and care is taken to remove excess alkali. Colour and perfumes are added to make these more attractive.
• Soaps that float in water are made by beating tiny air bubbles before their hardening.
• Transparent soaps are made by dissolving the soap in ethanol and then evaporating the excess solvent.
• In medicated soaps, substances of medicinal value are added. In some soaps, deodorants are added.
• Shaving soaps contain glycerol to prevent rapid drying. A gum called, rosin is added while making them. It forms sodium rosinate which lathers well.
• Laundry soaps contain fillers like sodium rosinate, sodium silicate, borax and sodium carbonate.
• Soap chips are made by running a thin sheet of melted soap onto a cool cylinder and scraping off the soaps in small broken pieces. Soap granules are dried miniature soap bubbles. Soap powders and scouring soaps contain some soap, a scouring agent (abrasive) such as powdered pumice or finely divided sand, and builders like sodium carbonate and trisodium phosphate. Builders make the soaps act more rapidly.

Why do soaps not work in hard water?

Hard water contains calcium and magnesium ions. These ions form insoluble calcium and magnesium soaps respectively when sodium or potassium soaps are dissolved in hard water. These insoluble soaps separate as scum in water and are useless as a cleansing agent. In fact, these are hinderance to good washing because the precipitate adheres to the fibre of the cloth as gummy mass.

Hair washed with hard water looks dull because of this sticky precipitate. Dye does not absorb evenly on cloth washed with soap using hard water, because of this gummy mass.

Detergents:

Detergents are sodium salts of long chain alkyl sulphates or a long chain of alkyl benzene sulphonate. They can be used both in soft and hard water as they give foam even in hard water. Some of the detergents give foam even in ice cold water.

Classification of Synthetic Detergents:

Synthetic detergents are mainly classified into three categories: Anionic detergents, Cationic detergents and Non-ionic detergents

Anionic Detergents:

Anionic detergents are sodium salts of sulphonated long-chain alcohols or hydrocarbons. Example: Sodium n-dodecyl benzene sulphonate

Alkyl hydrogen sulphates formed by treating long chain alcohols with concentrated sulphuric acid and neutralized with alkali to form anionic detergents.

Similarly, alkyl benzene sulphonates are obtained by neutralising alkyl benzene sulphonic acids with alkali.

In anionic detergents, the anionic part of the molecule is involved in the cleansing action. Sodium salts of alkyl benzene sulphonates are an important class of anionic detergents. They are mostly used for household work. Anionic detergents are also used in toothpaste.

Cationic Detergents:

Cationic detergents are quarternary ammonium salts of amines with acetates, chlorides or bromides as anions. The cationic part possesses a long hydrocarbon chain and a positive charge on the nitrogen atom. Hence, these are called cationic detergents. Example: Cetyltrimethylammonium bromide. It is a popular cationic detergent and is used in hair conditioners.

Cationic detergents have germicidal properties and are expensive, therefore, these are of limited use.

Non-ionic Detergents:

Non-ionic detergents do not contain any ion in their constitution. Example: Pentaerythrityl stearate

One such detergent is formed when a stearic acid reacts with polyethene glycol.

Liquid dishwashing detergents are a non-ionic type.

Mechanism of cleansing action of this type of detergents is the same as that of soaps. These also remove grease and oil by micelle formation.

Ecological Problem with Detergents:

The main problem that appears in the use of detergents is that if their hydrocarbon chain is highly branched, then bacteria cannot degrade them easily. Their slow degradation leads to their accumulation. Effluents containing such detergents reach the rivers, ponds, etc. These persist in water even after sewage treatment and cause foaming in rivers, ponds and streams and their water get polluted. These days the branching of the hydrocarbon chain is controlled and kept to the minimum. Unbranched chains can be biodegraded more easily and hence pollution is prevented.

Cleansing Action of Soaps and Detergents:

Soaps and detergents have two parts, the hydrophobic part and the hydrophilic part.

Hydrophobic or water repelling non-polar part (usually a long hydrocarbon chain) is soluble in oil and greases but insoluble in water. Hydrophilic or water attracting polar parts such as carboxylic group or sulphonate or sulphate is soluble in water and insoluble in oil and greases.

Molecules of soap and detergent form micelles in water. The hydrophobic part of soap dissolves in oil and grease while hydrophilic part of soap remains as free in soap solution. When the cloth is rubbed with hand or stirred mechanically, the big molecules of oil and soap break into small emulsified oil droplets.

These oil droplets repel each other due to the presence of anions of the hydrophilic part and do not precipitate. Thus they remain suspended in the soap solution without getting back on the cloth. These suspended oil and grease particles are then washed away by a stream of water.

Characteristics of Soaps:

• Soaps used for cleaning purpose are sodium or potassium salts of long chain fatty acids.
• They cannot be used in hard water or acidic solution as they precipitate out.
• They are biodegradable and hence they do not cause water pollution.
• e.g., stearic, oleic and palmitic acids.

Characteristics of Detergents:

• Detergents are sodium salts of long chain alkyl sulphates or a long chain of alkyl benzene sulphonate.
• Thay can be used in hard water and acidic medium.
• They are not biodegradable. Hence they cause water pollution.
• e.g. Sodium n-dodecyl benzene sulphonate, Cetyltrimethylammonium bromide, Pentaerythrityl stearate

Advantages of Detergents Over Soaps:

• Detergents can be used in hard water and acidic medium. While Soaps cannot be used in hard water or acidic solution as they precipitate out.
• Synthetic detergents have more solubility in water than soaps and hence they produce more lather.
• The cleansing action of detergents is stronger and efficient than soaps.

Science > Chemistry > Everyday Chemistry > Cleansing Agents: Soaps and Detergents

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In the last two articles, we have studied the use of chemicals as everyday medicines. In this article, we shall study the use of chemicals in food. The use of chemicals in food is in the form of food additives, food preservatives, artificial sweeteners, and antioxidants.

Food Additives:

To increase shelf life and to make food attractive various chemicals are added to food. Main categories of food additives are food colours, flavours and sweeteners, antioxidants, fat emulsifiers, stabilizing agents, flour improvers, food preservatives, and nutritional supplements like minerals, vitamins, and amino acids. Except for nutritional supplement, no other additive has any nutritional value.

Food Preservatives:

Food preservatives are the substances when added to food is capable of inhibiting, retarding or arresting the process of fermentation, acidification or other decomposition of food by the growth of microbes.

Examples: Sodium benzoate, salt of the ascorbic acid and propionic acid etc.

Food preservatives are classified into two groups – Class I and Class II.

• Class – I preservatives include table salt, sugar, and vegetable oils.
• Class- II preservatives include chemical preservatives like sodium benzoate, sodium meta-sulphide.

In India chemical preservatives like benzoic acid or its sodium salt and potassium metabisulphite or sodium metal sulphide are permitted.

Characteristics of Food Preservatives:

• It should not be harmful to human being.
• It should inhibit the growth of microorganism even if it is used in traces.

The Necessity of Food Preservation:

• To make the food available during the days of scarcity.
• To make fruit palatable, attractive and to increase its shelf life.
• To prevent spoilage of food by retarding or inhibiting the growth of microorganisms due to fermentation or acidification.
• To avoid undesirable changes that occur in colour, taste, flavour of the food.

Physical Methods of Food Preservation:

• By Removal of Heat (Cooling): This method involves refrigeration, freezing, dehydro-freezing, or carbonation. At low temperatures, the growth of the organism is inhibited. Cooling lowers the temperature of the substance which prevents the growth of the microorganisms. Fresh fruits, vegetables are preserved by this method.
• By Addition of Heat: This method involves pasteurization or sterilization. This process is also called as canning or heat processing. Heating kills microorganisms. Hence solid and liquid foods can be preserved by heating it. Pasteurization is a sterilization process for preserving food by the addition of heat or by increasing temperature. Pasteurization of milk is an example of this process.
• By Removal of Water (Dehydration): This process involves sun drying, freeze-drying, and puff drying. As water is removed the growth of the organisms is prevented. Fishes, fruits, vegetables, and food grains are preserved by this method.
• By Irradiation: This method involves ultraviolet or ionizing radiation. Irradiation controls the growth of microorganisms. High energy electromagnetic radiation produces desired effects without inducing radioactivity in food. Bakery products are preserved by this method.

Chemical Methods of Food Preservation:

• By Addition of Sugar: In this method, sugar is added to the food which is to be preserved and is then heated. This method is simple and cheap. This method is used to preserve fruit jams, jellies, and marmalades.
• By the addition of salt: Salt is added during the preparation of the product. Making pickles of raw mango, lemon, chilies, and preservation of fish products involve this method.
• By Addition of Vinegar: Dilute acetic acid commonly known as vinegar is added to food for preservation. This method is used for the preservation of pickles of raw mango, lemon, chilies salad dressing, and preservation of fishes.
• By Addition of Chemicals: Sodium benzoate, salt o the ascorbic acid and propionic acid, etc. are used as food preservatives. They inhibit the growth of microorganisms. These are added in small quantities to food like jams, jellies, and juices.

Chemicals Used in Food Preservations:

Sodium benzoate:

Benzoic acid or its salt of sodium benzoate are used as common food preservatives. It is soluble in water and also soluble in food products. 3. 0.06 % to 0.1 % concentration of sodium benzoate is sufficient for the preservation of fruit juices and squashes. Sodium benzoate is metabolized by conversion to hippuric acid which is finally excreted in the urine.

Potassium metabisulphite and Sodium meta sulphide:

It is used for preservation of colourless food materials such as fruit juices, squashes, apples, litchies and raw mango chutney. These preservatives react with the acid in the fruit juice producing sulphur dioxide which is very effective in killing the harmful microorganisms present in the food and thus prevents it from getting spoiled.

These are not used for preservation of coloured food material because the sulphur dioxide produced from these chemicals act as a bleaching agent and decolourises the food material.

Latest Methods of Food Preservation:

• The latest methods of food preservation are vacuum packing, freeze drying, ultraviolet or ionizing radiation. Using these methods microorganisms are destroyed.
• Irradiation by gamma rays prevents spoilage of potatoes and onions.

Artificial Sweeteners:

Natural sweeteners, e.g., sucrose add to calorie intake and therefore many people prefer to use artificial sweeteners. Natural sweeteners are metabolized in the body. Excess consumption of sugar leads to many diseases such as obesity, diabetes, coronary heart diseases.

The chemical compounds which do not occur in nature but are synthesized in the laboratory have a sweet taste, but they have no food value (they have very low-calorie value) are called artificial sweeteners. They are imparting sweetness but not adding any calorie value to the food. They pass through the human digestive system without being digested. Hence they are used for making sweets. Such sweets can be consumed by the diabetic patient also.

Saccharin:

Ortho-sulphobenzimide, also called saccharin, is the first popular artificial sweetening agent. It has been used as a sweetening agent ever since it was discovered by Constantine Fahlberg and Era Ramsen in 1879.

It is about 550 times as sweet as cane sugar. It is excreted from the body in urine unchanged. It appears to be entirely inert and harmless when taken. Its use is of great value to diabetic persons and people who need to control the intake of calories.

Aspartame:

Aspartame is the most successful and widely used artificial sweetener. It is roughly 100 times as sweet as cane sugar. 2. It is methyl ester of dipeptide formed from aspartic acid and phenylalanine.

Use of aspartame is limited to cold foods and soft drinks because it is unstable at cooking temperature.

Alitame:

Alitame is high potency sweetener, Hence it is difficult to control the sweetness of food while using this sweetener.

It is more stable than aspartame, the control of the sweetness of food is difficult while using it. It is 2000 times sweeter than sucrose.

Sucralose:

Sucralose is a trichloro derivative of sucrose. Its appearance and taste are like sugar.

It is stable at cooking temperature. It does not provide calories. It is 600 times sweeter than sugar.

Note: The use of cyclamates as sweetening agent has been banned in many countries in view of suspected carcinogenic effects.

Edible Colours:

Adding colours to the food makes the food more attractive, more acceptable and palatable. Colour has therapeutic value. The edible colours are classified into three types a) natural colours, b) browning colours produced during cooking and c) additives. Natural colours are

• carotenoids – yellow to red colours
• chlorophyll – green colour flavonoids (anthocyanins) – red to blue colour
• Anthocyanins are widely used in the food and their sources are grapes, beetroot, sweet potato, cabbage etc.
• Natural colour carotene is safe to be used in food.

Chemical dyes i.e. additives have stronger colours than the natural colours. Generally, they are azo dyes. They are not good for health. Tetrazine is a dye used in food for giving it colour.

Some additives are Chocolate Brown, Quinoline yellow WS, Sunset yellow, Allura red AC, Patent Blue V, Green S, Red 2G etc.

Antioxidants:

Antioxidants are the substances which when added to food, retard or prevents oxidative deterioration of food.

Examples: Butylated hydroxyanisole (BHA) and Butylated hydroxytoluene (BHT), Vitamin E is a natural antioxidant.

During the oxidation of food free radicals are generated. Antioxidants when added to food, react with these free radicals and prevent further oxidation and food becoming rancid.

Butylated hydroxyanisole (BHA):

Its chemical name is 2-tertbutyl-4-methoxy phenol. Its molecular formula is C₁₁H₁₆O₂.

It is found in butter, meats, cereals, chewing gum, snack foods, baked foods, beer and dehydrated potatoes. It is also found in rubber products, cosmetics, and petroleum products. It is used to preserve food. It is used in cosmetics, pharmaceutical, animal feed.

Butylated hydroxytoluene (BHT):

Its chemical name is 2,6-Di-tertbutyl-p-cresol. Its molecular formula is C₁₅H₂₄O.

Fat reacts with oxygen to form free radicals which react further with BHT to form stable BHT radical. This radical does not further react with molecules of fat and thus the chain reaction is stopped. By this way, BHT prevents rancidity of fats and hence it is used to preserve colour, odour and taste of foodstuff.

Sulphur dioxide and Sulphite:

The salts of sodium and potassium sulphite and bisulphites are used as antioxidants. Sulphur dioxide is widely used as preservative and antioxidant in food and beverage industries. Sulphites are used as antioxidants. They reduce discolorization of fruits, vegetables, and dehydrated potatoes.

Sulphites are used to preserve wine, dairy products, sauces, jams jellies etc. They are used as food additives as antimicrobial agents, structure modifiers, enzyme inhibitors.

In the next article, we shall study about cleansing agents: Soaps and detergents

Previous Topic : Antimicrobials, Antibiotics, Sulpha Drugs, Antiseptics, Disinfectants

Next Topic: Cleansing Agents: Soaps and Detergents

Science > Chemistry > Everyday Chemistry > Use of Chemicals in Food

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In the last article, we have studied medicines in everyday life, like analgesics, antipyretics, antihistamines, tranquilizers, antifertility, and antimalarials. In this article, we shall study, antimicrobials, antibiotics, antiseptics, and disinfectants.

The action of Microbes in the Body:

The living organisms which cannot be seen with the naked eyes (unaided eyes) and can only be observed through a microscope are called microorganisms or microbes. They include bacteria, fungi, algae, and viruses. They are present almost everywhere air, water, soil, inside and on our body. The disease-producing microbes are called pathogens.

Our body has an efficient defense structure against these pathogens. Skin prevents microbes to enter our body. Some secretions like lysosomes in tears, nasal secretions, saliva, fatty acids, lactic acid in sweat, hydrochloric acid in stomach kill these microbes or inhibit their growth. The breach of this defense system allows the pathogens to reach tissues and cause infection in the body. Due to which normal metabolic activities are disturbed.  This results in a disease. Pathogens produce toxins which may affect tissues and organs of the host.

Antimicrobials:

Antimicrobials are drugs which tend to destroy/prevent development or inhibit the pathogenic action of microbes such as bacteria (antibacterial drugs), fungi (antifungal agents), virus (antiviral agents), or other parasites (antiparasitic drugs) selectively. Antibiotics, antiseptics, and disinfectants are antimicrobial drugs.

The antimicrobials that kill bacteria are called bactericidal. Those inhibit the growth of bacteria are called bacteriostatic. Some antimicrobial increase immunity of the body. Germbacteriologistist Paul Ehrlich developed the first antimicrobial called arsphenamine (Salvarsan) for treatment of syphilis.

Sulpha drugs like sulphadiazine, sulphathiazole, sulphanilamide, sulphacetamide, sulphafurazole have great antibacterial power.

Antibiotics:

Antibiotics are used as drugs to treat infections because of their low toxicity for humans and animals. Initially, antibiotics were classified as chemical substances produced by microorganisms (bacteria, fungi, and molds) that inhibit the growth or even destroy microorganisms. The development of synthetic methods has helped in synthesizing some of the compounds that were originally discovered as products of microorganisms. Also, some purely synthetic compounds have antibacterial activity, and therefore, the definition of antibiotic has been modified. An antibiotic now refers to a substance produced wholly or partly by chemical synthesis, which at low concentrations inhibits the growth or destroys microorganisms by intervening in their metabolic processes.

The complete range of microorganisms which are attacked by an antibiotic is called a spectrum. The antibiotics effective against several different types of harmful microorganisms are called broad-spectrum antibiotics. e,g, Tetracycline, Chloramphenicol, etc.

In 1929 Alexander Fleming found antibacterial properties of a Penicillium fungus.

By substitution of different R groups, about 6 natural penicillins have been isolated so far. following five are from these 6 types.

Ampicillin and amoxicillin are semi-synthetic modifications of penicillin.

It is absolutely essential to test the patients for sensitivity (allergy) to penicillin or its modifications ampicillin and amoxicillin before it is administered.

In India, penicillin is manufactured at the Hindustan Antibiotics in Pimpri, at Indian Drugs and Pharmaceuticals Limited at IDPL Rishikesh and in private sector industry.

Types of Antibiotics:

Depending Upon Effect:

Antibiotics have either cidal (killing) effect or a static (inhibitory) effect on microbes. Depending upon these effects antibiotics are classified into two types bactericidal and bacteriostatic respectively.

• Examples of bactericidal antibiotics: Penicillin, Ofloxacin, Aminoglycosides, etc.
• Examples of bacteriostatic antibiotics: Erythromycin, Tetracycline,  Chloramphenicol, etc.

Depending Upon Spectrum:

The range of bacteria or other microorganisms that are affected by a certain antibiotic is expressed as its spectrum of action. The complete range of micro-organisms attacked by an antibiotic is called spectrum.

• Antibiotics which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria are said to be broad-spectrum antibiotics. Ampicillin and Amoxycillin are synthetic modifications of penicillin are broad spectrum Antibiotics. Other examples are tetracycline, chloramphenicol, vancomycin, ofloxacin.
• Antibiotics effective mainly against Gram-positive or Gram-negative bacteria are narrow spectrum antibiotics. e.g. Penicillin G5. Antibiotics effective against a single organism or disease, they are referred to as limited spectrum antibiotics.

Some Important Antibiotics:

Chloramphenicol is a broad spectrum antibiotic. It is rapidly absorbed from the gastrointestinal tract and hence can be given orally in case of typhoid, dysentery, acute fever, whooping cough, a certain form of urinary infections, meningitis, and pneumonia.

• Vancomycin and ofloxacin are the other important broad-spectrum antibiotics.
• The antibiotic dysidazirine is supposed to be toxic towards certain strains of cancer cells.
• Streptomycin is used for the treatment of tuberculosis. In low concentration it is bacteriostatic and in high concentration it is bactericidal.
• p-Aminosalicylic acid (PAS) and isonicotinhydrazine or isoniazid (INH) are also used for the treatment of tuberculosis.

Sulpha Drugs:

Sulpha drugs are derivatives of sulphanilamide. They were first introduced as medicine by Gerhard Domagk in 1930.

Sulphapyridine – Cure for pneumonia

Sulphadiazine – Cure for pneumonia, throat infection, meningitis,

Sulphaguanidine – Cure of bacillary dysentery

Sulphathiazole – Useful against staphylococcal infections and bubonic plague.

Succinyl sulphathiazole – Useful in intestinal infections such as bacillary dysentery and cholera)

Sulphaacetamide – Used to cure urinary tract infections.

Antiseptics:

Drugs which are applied to the living tissues to kill the bacteria and to stop their growth in
wound thus preventing its infection are called antiseptics.

Examples: Iodoform, boric acid, dilute solution of phenol, hydrogen peroxide. Dettol, tincture iodine, soframycin, furacine.

Antiseptics prevent the wound from infection. It is to be noted that antiseptics do not heal wounds. 2 to 3 % solution of iodine in alcohol and water is called tincture iodine. It is a powerful antiseptic and is applied to wounds.

Dettol is antiseptic and a mixture of terpineol and chloroxylenol.

Bithional (the compound is also called bithionol) is added to soaps to impart antiseptic properties.

Boric acid in dilute aqueous solution is weak antiseptic for eyes. Antiseptics are mixed with deodorants, face powders, and breath purifiers. Amyl meta-cresol is used as antiseptics in mouthwash or for gargling.

Uses of Antiseptics:

• They are used to dress the wounds.
• They are used to destroy fungal growth.
• They are used to sterilize surgical instruments.
• They are used in anti-infective in deodorants, shampoos and surgical soaps.

Disinfectants:

Drugs which are applied to the nonliving objects to kill the bacteria and to stop their growth are called disinfectants. They are not safe to be applied to living tissues.

Examples: Concentrated solution of phenol, sulphur dioxide, chlorine, Chlorine in the concentration of 0.2 to 0.4 ppm in aqueous solution. Sulphur dioxide in very low concentrations are disinfectants.

Uses of Disinfectants:

• They kill microorganisms on nonliving objects and used on public health floor and
  to sterilize the surgical instruments.

Difference Between Antiseptics and Disinfectants:

Antiseptics:

• Drugs which are applied to the living tissues to kill the bacteria and to stop their growth in wound thus preventing its infection are called antiseptics.
• Antiseptics are applied to the living tissues such as wounds, cuts, ulcers and diseased skin surfaces.

Disinfectants:

• Drugs which are applied to the nonliving objects to kill the bacteria and to stop their growth are called disinfectants.
• Disinfectants are applied to inanimate objects such as floors, drainage system, instruments.

Important Discoveries in the Field of Medicine:

• Fellix Hoffman (German chemist) – Synthesis of Aspirin
• LeoSternbach (Polish Jewish chemist) – Discovered benzodiazepines (A class of tranquilizers)
• Selman Waksman (Jewish American biochemist) – Discovery of Streptomycin
• Alexander Fleming (Scotish pharmacologist) – Discovery of penicillin
• Paul Ehrich (German scientist) – a compound containing arsenic to treat syphilis, Discovered salvarsan and protonsil.

In the next article, we shall study the chemicals in food.

Previous Topic: Analgesics, Antipyretics, Antihistamines, Tranquilizers, Antifertility drugs, and Antimalarials.

Next Topic: Use of Chemicals in Food

Science > Chemistry > Everyday Chemistry > Everyday Medicines 02

The post Everyday Medicines 02 appeared first on The Fact Factor.

In the last article, we have studied the mechanism of action of a drug. In this article, we shall study some everyday medicines like analgesics, antipyretics, antihistamines, antifertility, and tranquilizers.

Antipyretics:

Chemical substances that are used to bring down body temperature with high fevers are called antipyretics. They don’t have any effect on the human body when it is at normal temperature. This causes the body to lose heat and thus the temperature of the body decreases. Aspirin, Paracetamol, Analgin, Phenacetin acts as antipyretics.

Aspirin is common antipyretic. But it has the side effect. on hydrolysis, it gives salicylic acid which causes bleeding in the stomach. It should not be taken on an empty stomach. Some persons are allergic to aspirin. The usual allergic reactions are rashes on the skin, lowering of blood pressure, profuse sweating, intense thirst, nausea, and vomiting.

Calcium and sodium salts of aspirin are more soluble hence are less harmful. Aspirin has anti-blood clotting action. Hence it is used in the prevention of heart attacks. Other antipyretics used are novalgin, phenyl butazone, methacetin and butazolidine.

Chemical Names:

• Aspirin: 2-Acetoxybenzoic acid
• Paracetamol: 4-Acetamidophenol
• Phenacetin: N-(4-Ethoxyphenyl)acetamide
• Methacetin: 4-Methoxy acetanilide.

Preparation of Aspirin:

When salicylic acid is treated with the mixture of acetic anhydride and glacial acetic acid in presence of concentrated sulphuric acid, acetylation of salicylic acid takes place and aspirin is obtained.

Analgesics:

Analgesics are drugs which reduce or abolish pain without causing impairment of consciousness, mental confusion, incoordination or paralysis or some other disturbances of the nervous system.

Note: Aspirin, novalgin, phenacetin and combiflam act both as antipyreic as well as analgesic.

Analgesics are classified as follows:(i) Non-narcotic (non-addictive) analgesics(ii) Narcotic drugs

Non-narcotic (non-addictive) Analgesics:

Aspirin and paracetamol belong to the class of non-narcotic analgesics. Aspirin inhibits the synthesis of chemicals known as prostaglandins which stimulate inflammation in the tissue and cause pain. These drugs are effective in relieving skeletal pain such as that due to arthritis. These drugs have many other effects such as reducing fever (antipyretic) and preventing platelet coagulation. Because of its anti-blood clotting action, aspirin finds use in the prevention of heart attacks.

Some other analgesics are Novalgin, Butazolidine or phenylbutazone, ibuprofen, naproxen and diclofenac sodium or potassium.

Narcotic (addictive) Analgesics:

Morphine and many of its homologues, when administered in medicinal doses, relieve pain and produce sleep. Adverse effects are vomiting, dysphoria, fatigue, mental confusion. In poisonous doses, these produce stupor, coma, convulsions and ultimately death. They are very potent drugs and their chronic use leads to addiction.

Morphine narcotics are sometimes referred to as opiates since they are obtained from the opium poppy. Another source of narcotics is a marijuana plant. These analgesics are chiefly used for the relief of postoperative pain, cardiac pain and pains of terminal cancer, bone fracture, and in childbirth. These analgesic relieve pain but they attack the central nervous system and produce sleep and unconsciousness.

Other narcotic analgesics are codeine, pethidine hydrochloride, methadone, heroin etc.

Tranquilizers or Hypnotics:

Tranquilizers are a class of chemical compounds used for the treatment of stress, mental tension, anxiety, mania ( a disorder of mood), insomnia (sleeping sickness), discomfort feeling and mild or even severe mental diseases. Tranquilizers are also known as psychotherapeutic drugs.

These relieve anxiety, stress, irritability or excitement by inducing a sense of well-being. They form an essential component of sleeping pills.

Reserpine and chlorpromazine, two powerful tranquilizers were introduced simultaneously.

Examples: Equanil (controlling depression and hyper tension), valium (diazepam), veronol, meprobamate (relieving stress), chlordiazepoxide, serotonin etc. are mild tranquilizers. Other examples are amytal, seconal, librium,

Barbiturates:

The derivatives of the barbituric acid obtained by condensation of urea and malonic acid are called barbiturates.  They form another class of tranquilizers. Examples: Veronal, Amytal, Nembutal, luminal. Barbiturates act on the central nervous system and are hypnotic, i.e., sleep producing agents. Hence they are used to control hypertension and depression.

Treatment of Depression:

Noradrenaline is one of the neurotransmitters that play a role in mood changes. If the level of noradrenaline is low for some reason, then the signal-sending activity becomes low, and the person suffers from depression.

In such situations, antidepressant drugs are required. These drugs inhibit the enzymes which catalyze the degradation of noradrenaline. If the enzyme is inhibited, this important neurotransmitter is slowly metabolized and can activate its receptor for longer periods of time, thus the effect of depression is counteracted.

Drugs used are Iproniazid and phenelzine.

Side Effects of Tranquilizers:

They produce side effects like a headache, weight gain, discomfort, blurring of the vision.

Classifications of Drugs Used for Mental Treatment:

• Narcotics: used as analgesics and antidepressants. e.g. heroin, opium, pethidine.
• Hypnotics: used as tranquilizers and to reduce anxiety and mental tension. e.g. Equanil
• Sedatives (depressants): used to reduce the action of the central nervous system. They induce a feeling of relaxation, calmness, drowsiness, and reduces the wildness of the patient. e.g. valium, barbiturates
• Antidepressants: given to patients lacking confidence. They are called mood boosters. It induces a feeling of well being. e.g. Vitalin, Methadrine and cocaine.

Antifertility Drugs:

Antifertility drugs are the chemicals which are used to check pregnancy in women. These drugs control menstrual cycle and ovulation. These drugs are mainly used in the form of oral pills. The active ingredient in the pills acting antifertility agents are steroids.

The birth control pill is a mixture of synthetic estrogen and progesterone derivatives (synthesized steroids). They are more potent than natural hormones. Progesterone suppresses ovulation. Some of the contraceptive pills contain norethindrone (synthetic progesterone derivative) and ethynylestradiol (Novestrol) (synthetic estrogen derivative).

The active component of ‘morning after pill’ is a synthetic steroid mifepristone. It blocks the effect of progesterone and checks pregnancy.

Antacids:

Basic substances which neutralize the excess of hydrochloric acid in the stomach and raises the pH to appropriate level are called antacids

Examples: Magnesium hydroxide, aluminium hydroxide, Ranitidine (Zantac) is commonly used an antacid.

Overproduction of acid in the stomach causes irritation and pain. In severe cases, ulcers are developed in the stomach. The earlier treatment for acidity was the administration of antacids, such as sodium hydrogen carbonate or a mixture of aluminium and magnesium hydroxide.

However, excessive hydrogen carbonate can make the stomach alkaline and trigger the production of even more acid. Metal hydroxides are better alternatives because of being insoluble, these do not increase the pH neutrality.

These treatments control only symptoms, and not the cause. Therefore, with these metal salts, the patients cannot be treated easily. In advanced stages, ulcers become life-threatening and its only treatment is the removal of the affected part of the stomach.

A major breakthrough in the treatment of hyperacidity came through the discovery according to which a chemical, histamine, stimulates the secretion of pepsin and hydrochloric acid in the stomach. The drug cimetidine (Tegamet), was designed to prevent the interaction of histamine with the receptors present in the stomach wall. This resulted in the release of a lesser amount of acid. The importance of the drug was so much that it remained the largest selling drug in the world until another drug, ranitidine (Zintac), was discovered.

Pentaprazole and Omiprazole are the new drugs used to inhibit gastric secretion.

Antihistamines:

Antihistamines are the drugs that diminish or abolish the effects of histamine, a chemical released by most of the cells during an allergic reaction. Antihistamine by competing with histamine for binding sites of receptor where histamine exerts its effect. Basic Antihistamines are amines which are used as drugs to control allergy effects produced by histamine. Histamine is a potent vasodilator. It has various functions. It contracts the smooth muscles in the bronchi and gut and relaxes other muscles, such as those in the walls of fine blood vessels. Histamine is also responsible for the nasal congestion associated with the common cold and allergic response to pollen.

Synthetic drugs, brompheniramine (Dimetapp) and terfenadine (Seldane), act as antihistamines. They interfere with the natural action of histamine by competing with histamine for binding sites of receptor where histamine exerts its effect.

Antihistamines do not affect the secretion of acid in the stomach. The reason is that antiallergic and antacid drugs work on different receptors.

Examples: Synthetic drugs, brompheniramine (Dimetapp) and terfenadine (Seldane),

Other commonly used antihistamines are Diphenhydramine (Benadryl), pheniramine maleate (Avil), Chloropheniramine maleate (zeet), Chlorotheopyllinat (Avomine). They are used in hay fever, mild asthma, insect bites, cold etc.

The action of Microbes in the Body:

The living organisms which cannot be seen with the naked eyes (unaided eyes) and can only be observed through a microscope are called microorganisms or microbes. They include bacteria, fungi, algae, and viruses. They are present almost everywhere air, water, soil, inside and on our body. The disease-producing microbes are called pathogens.

Our body has an efficient defense structure against these pathogens. The skin prevents microbes to enter our body. Some secretions like lysosomes in tears, nasal secretions, saliva, fatty acids, lactic acid in sweat, hydrochloric acid in the stomach kill these microbes or inhibit their growth. The breach of this defense system allows the pathogens to reach tissues and cause infection in the body. Due to which normal metabolic activities are disturbed.  This results in a disease. Pathogens produce toxins that may affect tissues and organs of the host.

Anti-malarials:

Medicines used to bring down the body temperature during malaria fever are called antimalarials. Malaria is a highly widespread infectious disease caused by Sporozoa called plasmodium. Malaria is characterized by periodic fever, anaemia, and enlargement of liver and spleen. The four species Plasmodium vivax (fever on alternate days), Plasmodium malariae (fever once in three days), Plasmodium ovale (fever once in three days), Plasmodium falciparum (fever once in four days) are responsible for malaria in the human being. The choice of drug depends on the point of action of the drug.

Drugs used are

• Primaquine: It destroys sporozoites in the liver. Its long use is not advisable because it is highly toxic.
• Chloroquine, Proquanil, Pyimethamine: These drugs kill the parasite in the blood.

Previous Topic: Mechanism of Action of Drugs

Next Topic: Antimicrobials, Antibiotics, Sulpha Drugs, Antiseptics, Disinfectants

Science > Chemistry > Everyday Chemistry > Everyday Medicines 01

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In this article, we shall study the meaning of the term drug, and the mechanism of actions of drugs.

Drugs:

The word dug is derived from a French word drogue which means a dry herb. Drugs are chemicals of low molecular mass which interact with macromolecular targets and produce a biological response. Drugs may be a single chemical substance or a combination of two or more different substances. Example: Aspirin, Naproxen

Medicine:

When the biological response of a drug is therapeutic and useful, the drugs are called medicines. Medicine is defined as a chemical substance which is used for the purpose of diagnosis, prevention, cure or relief of disease and for reducing sufferings from pain.

Chemotherapy:

The term chemotherapy was coined by Paul Ehrlich. Paul Ehrlich is known as the father of modern chemotherapy. Chemotherapy is a specific treatment of a disease by the administration of chemical compounds used as medicines. The chemicals so used for the cure are called chemotherapeutic agents.

Characteristics of Ideal Drug:

• It should destroy disease-causing organisms without harming the human body.
• It should not disturb physiological processes in the human body.
• It should not injure host tissues.
• It should have minimum side effects.
• It should be localized to the affected site and should not interfere with the working of other parts.
• The cells should not acquire resistance to the drug after some time.

Methods of Administration of a Drug:

• Oral: tablets, syrups, mixtures administered through the mouth.
• Intravenous: injected directly into the bloodstream.
• Intramuscular:  injection in muscles
• Subcutaneous: injection under the skin
• Nasal: inhalation of a drug.
• Topical: local application e.g. oils, ointments.

Classification of Drugs:

Need for Classification of Drugs:

• It helps to select a proper drug for the treatment of a disease.
• It helps in studying the drug and to do research to overcome the side effects of the drug.
• It also helps in the development of new drugs.
• It helps for pharmacists to design a drug most effective for a particular receptive site.

Classification  Based on Pharmacological Effects:

This classification of drugs is based on the choice of drug and its pharmacological effect. This classification gives a whole range of drugs available for the treatment of a particular type of health disorder. Hence this classification is useful for doctors. Examples:

• Analgesics: Painkilling effect
• Antibiotics: To arrest the growth and kill bacteria
• Antiseptics: To arrest the growth and kill bacteria
• Tranquilizers: To reduce mental stress

Classification Based on the Action of Drugs:

These drugs are diseases oriented and have a different biological mode. Examples: painkillers, antiarthritic, antihistamines medicines. All antihistamines inhibit the (stops) action of the compound histamine which produces allergic reactions such as inflammation in the body.

Classification Based on Chemical Structure:

This classification of drugs is based on the assumption that drugs having similar chemical structures are expected to have similar pharmacological properties. Examples: All sulphonamides having a similar type of chemical structure show antibacterial activity.

Classification Based on Molecular Targets:

Drugs interact with biomolecules like carbohydrates, proteins, lipids, nucleic acids, etc. These are target molecules and the drugs are called target-oriented drugs. This classification is useful for medicinal chemists. Examples: Many enzymes and receptors in cells have molecular targets.

Classification of Drugs by Lay Public:

This is not a scientific classification but commonly used by the lay public. This classification is based on the action of the drug and not on the chemistry of a drug or biological action of the drug. Examples: Cough syrups, analgesics, laxatives, and purgatives.

Designing of a Drug:

Drug target and drug metabolism are the two main aspects considered during drug design. Knowledge of drug target and drug metabolism helps medicine chemists to develop new and improved drugs.

Drug Target:

Drugs interact with biomolecules like carbohydrates, proteins, lipids, nucleic acids, etc. These molecules are called target molecules. To obtain a desired therapeutic result the correct choice of a target for a drug is to be done. The site on which the drug acts is called receptor. Usually a protein or proteinaceous material acts as a receptor.

Drug Metabolism:

A drug travels through the human system in order to reach the target. So the drug should be designed in such a way that it reaches the target without being metabolized in between (i.e. site of administration to site of action). After the action of the drug at the receptor site, the side products of the drug (metabolites) should be excreted without causing harm to the body.

After considering the above points a drug is designed from such compounds which are called lead compounds and chosen as starting points for drug designing. Lead compounds may be obtained from natural sources like plants, trees, venoms and metabolites of organisms or they may be synthesized.

Drug-Target Interaction:

Drugs interact with biomolecules like carbohydrates, proteins, lipids, nucleic acids, etc. These molecules are called target molecules. Biomolecular macromolecules perform the following functions.

• The proteins which perform the role of biological catalysts in the body are called enzymes.
• Proteins which are crucial to the communication system in a body are called receptors.
• Proteins which carry polar molecules across the cell membrane are called carrier proteins.
• Nucleic acids have coded genetic information for the cell and lipids.
• Carbohydrates are the structural part of the cell membrane.

Enzymes as Drug Targets:

The enzymes are biological catalysts. They provide active sites which hold the substrate molecule in a suitable position so that it can be attacked by the reagent effectively. The substrate binds to amino acids of the protein present on active site through interactions like ionic bonding, hydrogen bonding, van der Waals’ interaction or dipole-dipole interaction.

Enzyme provides functional groups that will attack the substrate and carry out a chemical reaction. Drugs inhibit the action of enzymes. Such drugs are called enzyme inhibitors. Thus enzyme inhibitors block the binding site and prevent binding of substrate. They also inhibit the catalytic action of enzymes.

Drug – Enzyme Interaction:

Drugs inhibit the attachment of the substrate on the active site of enzymes in two ways.

Competitive inhibitor’s action:

Such inhibitors compete with the natural substrate for the active site. Hence such inhibitors are called competitive inhibitors.2. In such cases, the drug occupies the position available for the substrate and thus prevents the substrate to occupy the active site on the enzyme. Thus the action of the enzyme is inhibited.

Noncompetitive inhibitors action:

Some drugs do not bind to active sites but bind to a different site of enzyme which is called allosteric sites. Doing this changes the shape of the active site.

Due to the change in the shape of the active site, the substrate cannot recognize the active site. These inhibitors are called non-competitive inhibitors.

Note:

If the bond formed between the drug and the enzyme is strong covalent bond and can not be broken easily then the enzyme is blocked permanently. Then the body degrades the blocked enzyme and synthesizes new enzymes.

Receptors as Drug Targets:

Receptors are proteins which are crucial for body’s communication process. Most of them are embedded in cell membranes such that their small part possessing active site projects out of the surface of the membrane and opens outside of the cell membrane. The chemical messages like neurotransmitters and hormones are received at the binding site of the receptor protein.

To accommodate the Messenger the shape of the receptor changes and this message is transferred into the cell without entering into the cell. When the chemical messenger leaves the site, the receptor regains its original shape.

There are large numbers of different receptors in the body and they interact with different chemical messengers. These receptors show the selectivity of one chemical messenger over the other due to their different shape, structure and amino acid composition at binding sites.

Drug – Receptor Interaction:

Drugs may bind to the receptor site and inhibit its natural function, such drugs are called antagonists. Some drugs mimic the natural messenger by switching on the receptor. Such drugs are called agonists. These are used when there is lack of natural messengers.

There are some receptors which interact with a particular messenger but they differ in their binding sites. For example, there are two types of adrenergic receptors namely α adrenergic receptors and β adrenergic receptors. Both of these receptors can bind adrenaline or epinephrine. It is possible to design drugs which will bind better with one type of adrenergic receptor than the other.

The receptors are not distributed uniformly around the body. For example, The heart has more β adrenergic receptors than α adrenergic receptors. Thus the drug designed to interact β adrenergic receptors will act more on the heart rather than on tissues which are rich in α adrenergic receptors.

If the drug binds to more than one type of receptors then it causes side effects. Side effects can also arise if the degradation product of the drug is biologically active and interacts with some other receptors.

In the next article, we shall study medicines in everyday life, like analgesics, antipyretics, antihistamines, antifertility, and tranquilizers.

Next Article: Analgesics, Antipyretics, Antihistamines, Tranquilizers

Science > Chemistry > Everyday Chemistry > Mechanism of Action of Drug

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