Eating Mangoes is possible only in summer season. But we make it possible to drink mango juice in all the seasons, as we are using food preservatives. Stress, strain, fever, disease ..... all can be cured by drugs and medicines. Cleansing agents keeps us away from the diseases. Thus chemistry is influencing our life every second, every minute, every day.
 

DRUGS
      Chemical substances having low molecular mass 100 - 500 U, those reacts with macro molecular target to produce a biological response is called "Drugs". Where as the drug that produce biological response therapeutically and useful in diagnosis, prevention and treatment of disease is called "Medicine". Use of chemicals for therapeutic effect (for treatment of diseases) is called "Chemotherapy".
Drugs are classified on the basis of pharmacological effect, on the basis of drug action, on the basis of chemical structure and on the basis of molecular targets. Proteins which perform role of biological catalysts are called "Enzymes" and which are crucial to communication system are called "receptors". The function of enzymes is to hold the reactant for a chemical reaction and to provide functional groups to attack with the reactants carry out the chemical reaction. Any drug that inhibits activity of enzyme is called "enzyme inhibitor". The drug that bind to the enzyme's active site is called "competitive inhibitor" and which do not bind is called "allosteric site". If the message is communicated through a chemical between two neurons & that between neuron and muscle, the chemical is called "chemical messenger". Drugs that bind to the receptor site and inhibit its natural action are called "antagonists" and the drugs that initiate the natural messenger by switching on the receptor are called "Agonists".
 

Therapeutic Action of Drugs
       Due to tensions, worries, life style, excess of acid is produced in the stomach, may cause ulcers. The chemical compound that removes excess of acid by neutralisation (by bringing pH to the normal level in stomach is called "Antacid" (e.g.: Omeprazole, Lansoprazole). Later we came to know that Histamine stimulates the secretion of Pepsin and HCl in the stomach. Drugs like Cimetidine (Tegament), Ramitidine (Zantac) were designed to prevent the interaction of Histamine with the receptors of stomach wall and these drugs are called "Antihistamines". Antihistamines like Seldane, Dimetane are used to cure nasal congestion, allergy and common cold.
         Analgesics and tranquilizers are neurologically active drugs. The drug used to reduce mental diseases and stress is called "Tranquilizer" (e.g.: Serotonin, Equanil, Valium). Tranquilizer also relieve anxiety and irritability. This drug is a part of sleeping pill. Noradrenaline changes mood. The drug that inhibit the enzyme and catalyse the degradation of Noradrenaline is called "antidepressant" (e.g.: Iproniazid, Phenelzine). Chlordiazepoxide, Meprobamate are used for relieving tension. Equanil is used to control depression and hypertension. Valium and Serotonin are also used as tranquilizers. Derivatives of barbituric acid (barbiturates) like Vereonal, Anytal, Membutal, Luminal, Seconal are hypnotic (sleep producing agents).

Analgesics are used to reduce pain. They are classified as:
Non-narcotic (Non-addictive) Analgesics: Chemical substances having no addictive property and relieves aches like head ache, back ache, skeletal pain (due to arthritis) are called "Non-Narcotic Analgesics". (e.g.: Aspirin, Paracetamol). These drugs also prevent fevers, platelet coagulation, blood clotting and heart attacks.
 

Narcotic (addictive) Analgesics: The alkaloid having addictive property that cause depression of central nervous system and relieves strong pains like cardiac pain, post operative pain, cancer pain and pains during child birth are called "Narcotic Analgesics".
(e.g.: Morphine, Heroin, Codeine).
 

Antimicrobials: The drugs used to inhibit the action of microbes like bacteria, fungi, virus etc. Antiseptics, antibiotics, disinfectants are antimicrobial drugs. The wonder drug Pencillin was discovered by Alexander Fleming. Azodyes, Salvarsan antibiotics were used for the treatment of syphilis. Sulphanilamide is another antibiotic. Antibiotic is a substance produced partly or fully by chemical synthesis, which inhibits the growth or destroys disease causing microorganisms. Antibiotics either kill bacteria (bactericidal e.g.: Pencillin, Aminoglycosides, Ofloxacin) or inhibit bacteria (bacteriostatic e.g.: Erythromycin, Tetracycline, Chloramphenicol). 

Antibiotics must be a product of metabolism, should be effective in low concentration, should retart the growth or survival of microorganisms, structure of synthetic antibiotic should be similar to naturally occuring antibiotic. Antibiotics which kill or inhibit wide range of gram positive & gram negative bacteria are called "broad spectrum antibiotics" (e.g.: Ampicillin, Amoxycillin, Chloramphenicol). Those which kill only gram positive or gram negative are called "Narrow spectrum antibiotics" (e.g.: Penicillin G). Chloramphenicol is used to cure typoid, dysentery, acute fever, urinary infections, Meningitis and Pneumonia.
       Wounds, cuts, diseased parts of skin, are to be treated with antiseptics like bithional, chloroxylenol, dettol, terpineol, tincture of iodin, iodoform and boric acid. The compound that prevent or kill the growth of microorganism is called "Antiseptic" (e.g.: Furacine, Soframicine). Dettol is a mixture of Chloroxylenol & Terpineol and widely used antiseptic. If the chemical used to kill or to prevent the growth of harmful microorganisms on floors, drainage system is called "disinfectant". 0.2% solution of Phenol is antiseptic, 1% Phenol is disinfectant. 0.2 to 0.4 ppm chlorine water and SO₂ (low concentration) are disinfectants.

Antifertility drugs: Oral contraceptives are used to control population. They controls female menstrual cycle and ovulation. Birth control pill is a mixture of steroids i.e. synthetic eastrogen & progesterone derivatives. e.g.: pills containing Norethindrone, Novestrol, Mifepristone. Mifepristone is used as a "morning after pill'. Synthetic steroid contains eastrogen & progesterone, used for birth control is called "antifertility drug".
 

Chemicals in Food
     Some chemicals are added to food for preservation, to enhance appeal, to increase nutritive value. Chemicals which are added to preserve food by preventing spoilage of food due to microorganism are called "food preservatives" (e.g.: salt, sugar, sodium benzoate). Food additives that are useful in the food preservation by retarding the action of food with Oxygen are called "Antioxidants" (e.g.: BHA, BHT, SO₂).
    The chemical substances not only controls the intake of calories but also gives sweet taste are called "artificial sweetening agents". (e.g.: Sucralose, Saccharin). Aspartane is 100 times, Saccharin is 550 times, Sucralose is 600 times, Alitame is 2000 times sweeter than that of cane sugar.

Cleansing Agents
     Detergents (soaps, synthetic detergents) are used as cleansing agents. The process of formation of soap by heating fat (glyceryl ester of fatty acid) like stearic, oleic, and palmatic acids with aqueous NaOH is called "Saponification". Potassium soaps are soft to the skin than sodium soaps.
      Toilet soaps are prepared by using high grade oils & fats, colour, perfumes, by removing excess of alkali. Shaving soaps are made of glycerol to prevent rapid drying. Laundry soaps contains some fillers like borax and Na₂CO₃. Soap powders, scouring soaps contain sand or Pumice, Na₂CO₃. As soaps form scum with hard water (due to Ca⁺², Mg⁺² ions). Synthetic detergents are used for cleansing purposes.
     Detergents with highly branched chain are non biodegradable and cause environmental pollution. So detergents with straight chain are preferred. The cleansing agents having properties of soap (but do not contain any soap), can be used either in soft water or in hard water or in ice cold water to produce foam are called synthetic detergents. They are classified into anionic, cationic and non-ionic detergents. Anionic detergents are sodium salts of sulphonated long chain hydrocarbons or alcohols.

e.g.:

                It is used in tooth paste and for household work.
Cationic detergents are quaternary ammonium salts of amines with anions  (Cl^-,Br^-,CH₃COO^-).

Cetyl trimethyl ammonium bromide

It is used in hair conditioners. They have germicidal properties. Non ionic detergents (e.g.: liquid washing detergents) do not contain any ion.
              

                                   Stearic acid                          Polyethylene glycol
              CH₃(CH₂)₁₆ COO(CH₂CH₂O)_n CH₂CH₂OH
This detergent removes grease and dirt or oil by micelle formation.