Natural Sources Of Drugs PDF

UNIT-II. Brief introduction to natural sources of drugs with examples: - Plant Source, - Animal Source, - Mineral Source, - Marine Source and - Microorganisms.  A large number of drugs are used in the clinics for the cure of various ailments.  These...

UNIT-II. Brief introduction to natural sources of drugs with examples: - Plant Source, - Animal Source, - Mineral Source, - Marine Source and - Microorganisms.  A large number of drugs are used in the clinics for the cure of various ailments.  These drugs are diverse in chemical structure and are obtained from a wide variety of sources.  In earlier days, simple chemical substances and different parts of plants were employed as medicinal agents, but most drugs currently used in therapeutics are synthetic in nature.  However, natural sources are still used for obtaining some drugs mainly because their synthesis is difficult and uneconomical. Drugs are mainly obtained from following sources. - Plant Source, - Animal Source, - Mineral Source, - Marine Source and - Microorganisms.  SOURCES I. NATURAL SOURCE A. Organic drugs. Organic drugs are mainly obtained from 1. Plant source 2. Animal source 3. Marine sources 4. Microorganisms. B. Inorganic drugs. These are mainly obtained from 1. Metallic source 2. Non-metallic source. II. SYNTHETIC SOURCE  (I) NATURAL SOURCES OF DRUGS Active principles of drugs are mainly present in crude form in minute amounts. These active principles are separated by various techniques or may be used as such in some cases. (A) Organic drugs: Main natural sources of organic drugs are plants, animals and microorganisms. 1. Plant source:  Plant sources Almost all parts of the plants are used i.e. leaves, stem, bark, fruits and roots. 1. Leaves The leaves of Digitalis purpurea are the source of Digitoxin and Digoxin, which are cardiac glycosides. Leaves of Eucalyptus give oil of Eucalyptus, which is important component of cough syrup. Tobacco leaves give nicotine. Atropa belladonna gives atropine. 2. Flowers Papaver somniferum gives morphine (opoid) Rose gives rose water, used as tonic 3. Fruits Senna pod gives anthracine, which is a purgative (used in constipation) Calabar beans give physostigmine, which is cholinomimetic agent 4. Seeds Seeds of Nux vomica give strychnine, which is a CNS stimulant. Castor seeds give castor oil. Calabar beans give Physostigmine, which is a cholinomimetic drug 5. Roots Ipecacuanha root gives Emetine, used to induce vomiting as in accidental poisoning. It also has amoebicidal properties. Rauwolfia serpentina gives reserpine, a hypotensive agent. Reserpine was used for hypertension treatment. 6. Bark Cinchona bark gives quinine and quinidine, which are antimalarial drugs Quinidine also has antiarrythmic properties. Atropa belladonna gives atropine, which is anticholinergic. Hyoscyamus niger gives Hyosine, which is also anticholinergic 7. Stem Chondrodendron tomentosum gives tuboqurarine, which is skeletal muscle relaxant used in general anesthesia  It is very old and important source of drugs, various parts of the plants are still used for drugs. The following table summarizes some Part of the plant Name of the plant Active Principle Use Root Rauwolfia Reserpine Antihypertensive pecacuanha Ipecac Emetic Bulbs Urginea Squill Emetic, rodenticide Bark Cinchona Quinine Antimalarial Rhizome Ginger Gingerol Carminative Wood Sandal wood Sandal wood oil Urinary antiseptic Quassia Quassin Stomachic Leave Belladona Atropine Anti-muscarinic Digitalis Digitoxin Cardiac stimulant Flower Clove Eugenol Local anaesthetic, rubefacient Pyrethrium Pyrethrin Insecticide Fruit Senna Senegrin Purgative Anise Anethole Carminative Seed Nux vomica Strychnine Rodenticide Physostigma Physostigmine Anti-glaucoma Corn Colchicum Colchicine Anti-gout  2. Animal sources : From animal source relatively few but important drugs are obtained. Following are some useful drugs: Hormones: Insulin, thyroxin, gonadotropins, etc. Vitamins: Cod liver oil (vit. A). Vaccines/serra: Anti-rabies vaccine (A.R.V), antitetanic serum (A.T.S), anti- diphtheric serum, etc. Replacement therapy : Liver extract.  Animal Sources Pancreas is a source of Insulin, used in treatment of Diabetes. Urine of pregnant women gives human chorionic gonadotropin (HCG) used for the treatment of infertility. Sheep thyroid is a source of thyroxin, used in hypertension. Cod liver is used as a source of vitamin A and D. Anterior pituitary is a source of pituitary gonadotropins, used in treatment of infertility. Blood of animals is used in preparation of vaccines. Stomach tissue contains pepsin and trypsin, which are digestive juices used in treatment of peptic diseases in the past. Nowadays better drugs have replaced them.  3. Marine sources Algae, the chlorophyll containing organisms known to have more than 20 000 species. The multicellular plants growing in salt or fresh water are known as Macro-algae or “seaweeds”. Due to their fast growing nature, they can size up to 60 m in length. Based on their pigmentation they are classified into three broad groups: i) brown seaweed (Phaeophyceae); ii) red seaweed (Rhodophyceae) and iii) green seaweed (Chlorophyceae) APPLICATIONS 1. Hydrocolloids Alginates from the cell wall of brown algae are polymers composed of D- mannuronic acid and L-guluronic acid monomers are used in food and pharmaceutical industries in the form of stabilizers for emulsions and suspensions Carrageenans from the cell wall of red algae have application in food, textile and pharmaceutical industries 2. Pharmaceuticals and cosmetics The micro-algae can produce bioactive compounds like antibiotics, algicides, toxins. A lot of antibiotics have been isolated from algae and show great chemical diversity (fatty acids, bromophenols, tannins, terpenoids, polysaccharides, alcohols). Most of them produce neurotoxic and hepatotoxic compounds Chlorella and Arthrospira (Spirulina) are used in skin care, sun protection and hair care products Agar is used as a thickening and water-binding agent as well as an antioxidant 2. Pharmaceuticals and cosmetics (cont.) As it is rich in vitamins and minerals, algae conditions and hydrates the skin while it nourishes, rejuvenates, detoxifies and replenishes minerals. The important form like Irish moss and carrageenan contain proteins, vitamin A, sugar, starch, vitamin B1, iron, sodium, phosphorous, magnesium, copper and calcium Algae products used as anticoagulants, antibiotics, antihypertensive agents, blood cholesterol reducers, dilatory agents, insecticides, and anti-tumorigenic agents. In cosmetics, algae products act as thickening agents, water-binding agents and antioxidants Microalgae Chlorella, Astaxhanthin and Spirulina have been found to possess anti-cancer, immune stimulatory, detoxifying, anti-diabetic, anti- inflammatory, antihypertensive and digestive properties Caulerpin in Red and Green algae control inflammation while sulphated polysaccharide act as pro-inflammatory. The fucodans, sulphated polysaccharide, of brown algae origin is also anti- inflammatory. The versatility of the green algae Chlamydomonas reinhardtii studied for the utilization in the drug industry. In the study it was found that it produced proteins at very high levels 4. High value oils Long-chain poly-unsaturated fatty acids (vlcPUFAs) eicosapentaenoic (EPA), docosahexaenoic acid (DHA) and arachidonic acid (AA) known for their nutritional importance. Interestingly the vlcPUFAs in the oil-rich fish originate from marine micro-algae that are eaten by the fish. Algal genes encoding relevant enzymes have been identified and recently several groups have reported progress on using these genes to produce DHA and ARA in transgenic plants, including crops such as soybean, linseed, tobacco and the model species Arabidopsis. By adding additional genes to the ones that are needed to produce ARA and EPA, production of DHA has been established in soybean, Brassica juncea and Arabidopsis. An alternative approach is to use directly the algae that are the most efficient primary producers of the vlcPUFAs. 5. Colourants Micro-algae produce carotenoids. More than 40 carotene and xanthophylls are well characterized. Xanthophyll a lutein has a huge application in the colouration of drugs and cosmetics. Phycobillins or phycobiliproteins are water soluble pigments, have their applications in cell biology as fluorescent markers, while the Phycobilins are also used as colorants for food and cosmetic products like a blue phycobilin from Arthrospira is used to colour cosmetics and food 6. Removal of heavy metals Algal biomass used as an inexpensive biomaterial for removal of toxic heavy metals. The use of micro algae for removal of heavy metals from waste water have huge application 7. Food Supplement As microalgae possess high-quality natural proteins, lipids, carbohydrates, vitamins, pigments and enzymes and therefore they can be used as food supplement at commercial levels. Omega-3 fatty acid extracted from algae are used as economical food supplement The edible seaweeds can be used as food supplement due to low calorie, high concentration of minerals, vitamins and proteins and low fat content. Blue green algae Spirulina as rich source of vitamin and minerals is used in food industry 7. Food Supplement (cont.) Several algae in red algae category like Porphyra and brown algae are directly consumed by human beings. Moreover the algae used in animals as food supplement is also an achievement. 8. As Human Food Some red algae, brown algae and green algae, are eaten by humans. Approximately 500 species are eaten by humans, and some 160 are commercially important. The red algae Porphyra is the most important commercial food algae. Palmaria palmata, another red algae, is eaten in the North Atlantic region. Laminaria species (brown algae) is eaten with meat or fish and in soups. The green algae Monostroma and Ulva look like lettuce leaves (their common name is sea lettuce), and they are eaten as salads or in soups, relishes, and meat or fish dishes. The microscopic, freshwater green algae Chlorella is cultivated and eaten in Taiwan, Japan, Malaysia, and the Philippines. It has a high protein content (53–65%) and has been considered as a possible food source during extended space Travel 9. Texturized vegetable protein The invention of digestible texturized algal protein, TAP, will ignite the use of algae in foods. TAP, Alnuts, Nostoc or other trade names may be used as a meat replacement or supplement. The extrusion technology changes the structure of the protein and yields a fibrous spongy matrix that is similar in texture to meat. TAP may be presented in a wide variety of traditional food forms such as sushi, diced chicken, turkey, tuna or red meats 10. HIV Vaccine model In the recent research it is found that algae-based proteins can inhibit the entry of the HIV virus. HIV vaccine grown in a designer strain of algae may be used with the defective cell wall technique to assure transgenic material does not escape into the environment. The vaccine cost would be lower as the algal production would be done locally. Instead of extracting the vaccine, people could eat the algae directly and let their bodies metabolize the vaccine. The same process may work for other vaccines such as mumps, measles, malaria, polio, tuberculosis and other preventable illnesses. There are many obstacles to the vaccine scenario, including bioethics, biotechnology and socio-culture issues. However, the simplicity and cost effectiveness of an algae solution would seem to make algae based vaccine model happen sooner rather than later 11. Personalized Drugs When markers are developed for personalized diagnosis, scientist will need drugs manufactured specifically to match the genetic needs of each patient and they are likely to need the drugs quickly. Personalized drugs and advanced compounds grown in algae may provide a cost effective solution. Such a production system could produce the designer drugs in days instead of months. While there is a critical global need for micro-algaculture systems, large scale systems are needed too 12. Food Additives The cell walls of many types of seaweed contain phycocolloids that have received increasing use in prepared foods. The three major phycocolloids are alginates, agars, and carrageenans. Alginates are extracted primarily from brown seaweeds, and agar and carrageenan are extracted from red seaweeds. Phycocolloids are safely consumed by humans and other animals and are therefore used in a wide variety of prepared foods, such as “ready-mix” cakes, “instant” puddings and pie fillings, and artificial dairy toppings  12. Food Additives (cont.) Alginates, or alginic acids, are commercially extracted from brown seaweeds, especially the kelp Macrocystis, Laminaria, and Ascophyllum. Alginates are used in ice creams to limit ice crystal formation, thereby producing a smooth texture, and are also used as emulsifiers and thickeners in syrups and as fillers in candy bars and salad dressings. Agars are extracted primarily from species of the red alga Gelidium, but they are also obtained from other red algae, especially Gracilaria, Pterocladia, Acanthopeltis, and Ahnfeltia. Agars are used in instant pie fillings, canned meats or fish, and bakery icings. Agar is also used as a clarifying agent in beer and wine. Carrageenan, from the Irish word “carraigin” (meaning Irish moss), are extracted from various red algae: Eucheuma in the Philippines, Chondrus crispus in the United States and the Canadian Maritime Provinces, and Iridaea in Chile. Carrageenans are used as thickening and stabilizing agents in dairy products, imitation creams, puddings, syrups, and canned pet foods. 12. Active Additives in Medical Drugs or Insecticides Phycocolloids have industrial uses in addition to their important roles in food products. Because they are relatively inert and have good gelling properties, they are used as creams and gels for carrying minute amounts of active additives, as in medical drugs or insecticides. Agar is used extensively as a bacteriologic culturing substrate in medical and research facilities and is also used as a substrate for eukaryotic cell and tissue culture, including the culture of algae themselves. Carrageenans are used in the manufacture of shampoos, cosmetics, and Medicines 13. Industrial Chemicals Algae are used for production or extraction of some important chemical that have wide industrial values. Iodine can be extracted from brown algae. The green unicellular flagellate Dunaliella is cultivated in saline ponds. The culture conditions are manipulated so that carotene or glycerol is produced in large amounts. These compounds are extracted and sold commercially. 14. Forensic Medicine Diatoms have been used in forensic medicine. Where death by drowning is suspected, lung tissue is examined. The presence of silica diatom cell walls can verify death by drowning; in mysterious cases, the diatom species can be used to pinpoint the exact location of death because the species are characteristic for a given lake, bog, or bay  4. Microorganisms : Microorganisms are also an important source of drugs. Certain bacteria, fungi and actinomycetes produce antibiotics which forms a major group of therapeutically useful drugs. Fungi : Penicillin G from Penicillium notatum. Actinomycetes : Streptomycin from Streptomyces griseus Bacteria : Bacitracin from Bacillus subtilus.  Bacterial sources of drugs Tetracycline Produced by filamentous bacteria-Actinomyces- mainly the mutants of Streptomyces aureofaciens - components of the soil Oxytetracycline -related analogue from S. rimosus Anthracyclic cpds Anti-tumour agents Minocycline and doxycycline-produced synthetically from natural tetracyclines Erythromycin A for Legionnaires’ disease(pneumonia) From Saccharopolyspora erythrea (Actinomycete) Clarithromycin & azithromycin- synthetic analogues The Statins Mevastatin -inhibits cholesterol synthesis; produced by Penicillium citrimum and Penicillium brevicompactum Lovostatin (methyl analogue)-from Monaseus ruber and Aspergillus terreus Simvastatin (Zocor)-dimethyl analogy of Mevastatin All are pro-drugs activated by hydrolysis Pravastatin (Lipostat)-semi synthetically produced by microbial hydrolysis of Mevastatin by Streptomyces carbophilus Bacterial sources of drugs(cont.) Actinobacteria give Streptomycin Aminoglycosides such as gentamycin and tobramycin are obtained from Streptomyces and micromonosporas Vaccines  PHARMACETICAL IMPORTANCE OF FUNGI 1. Introduction Cultivated or gathered for food Nutrition Mushrooms are a low-calorie food usually eaten cooked or raw and as garnish to a meal. Dietary mushrooms are a good source of B vitamins, such as riboflavin, niacin and pantothenic acid, and the essential minerals, selenium, copper and potassium. Fat, carbohydrate and calorie content are low, with absence of vitamin C and sodium. There are approximately 20 calories in an ounce of mushrooms Fungi have medicinal properties too  Medicinal value Pleurotus ostreatus (oyster mushrooms) Pleurotus ostreatus (oyster mushrooms) The chemical nature of the bioactive compounds present in this mushroom includes: Polysaccharides, Lipopolysaccharides, Proteins, Peptides, Glycoproteins, Nucleosides, Triterpenoids, Lectins, Lipids and their derivatives Pleurotus ostreatus (oyster mushrooms) Pharmacological Activities Antineoplastic (inhibiting or preventing the growth and spread of tumors or malignant cells) Antiviral Antitumor Antimicrobial Antimutagenic Antilipidemic Hypocholesterolemic Immunomodulatory Hepatoprotective Anti-Inflammatory Aspergillus niger Aspergillus niger-industrial and medicinal uses Industrial preparation of citric acid (E330) and gluconic acid (E574) and have been assessed as acceptable for daily intake by the World Health Organisation A. niger fermentation is "generally recognized as safe" (GRAS) by the United States Food and Drug Administration under the Federal Food, Drug, and Cosmetic Act. Many useful enzymes are produced using industrial fermentation of A. niger. For example, A. niger glucoamylase is used in the production of high fructose corn syrup, and pectinases are used in cider and wine clarification. Alpha-galactosidase, an enzyme that breaks down certain complex sugars, is a component of Beano and other products that decrease flatulence (marked by or affected with gases generated in the intestine or stomach) Another use for A. niger within the biotechnology industry is in the production of magnetic isotope-containing variants of biological macromolecules for NMR analysis.  Penicillium notatum/Penicillium chrysogenum Source of penicillin discovered by Alexander Fleming Griseofulvin ( Grisovin) Produced by fungus mould Penicillium griseofulvum Systemic treatment of fungal dermatophytic infections for the skin, hair, nails and feet caused by fungi belonging to the genera Trichophyton, Epidermophyton and Microsporum Antibiotic used in veterinary medicine to treat ringworm in animals Claviceps purpurea Ergotamine Is an ergopeptine and part of the ergot family of alkaloids; It is structurally and biochemically closely related to ergoline. It possesses structural similarity to several neurotransmitters, and has biological activity as a vasoconstrictor It is used medicinally for treatment of acute migraine attacks (sometimes in combination with caffeine) Toxic fungi Amanita muscaria Fungal toxins Alpha-amanitin (deadly: causes liver damage 1–3 days after ingestion) – principal toxin in genus Amanita. Phallotoxin (causes gastrointestinal upset) – also found in poisonous Amanitas Orellanine (deadly: causes kidney failure within 3 weeks after ingestion) – principal toxin in genus Cortinarius. Muscarine (sometimes deadly: can cause respiratory failure) – found in genus Omphalotus. Gyromitrin (deadly: causes neurotoxicity, gastrointestinal upset, and destruction of blood cells) – principal toxin in genus Gyromitra. Coprine (causes illness when consumed with alcohol) – principal toxin in genus Coprinus. Ibotenic acid (causes neurotoxicity) and muscimol (causes CNS depression and hallucinations) – principal toxins in Amanita muscaria, A. pantherina, and A. gemmata. Psilocybin and psilocin (causes CNS arousal and hallucinations) – principal 'toxins' in psilocybin mushrooms, many of which belong to the genus Psilocybe. Arabitol (causes gastrointestinal irritation in some people). Bolesatine a toxin found in Boletus satanas Ergotamine (deadly: affects the vascular system and can lead to loss of limbs and death): An alkaloid found in genus Claviceps  (B) Inorganic Sources (Mineral sources): Drugs obtained from inorganic sources have been simply classified into metals and non-metals. Metalloids which show intermediate properties are usually discussed along with metals. The elements either occur in native state or combined state.  1. Metals : Minerals are the main source of metals. Agent Use Magnesium sulphate Purgative Calcium carbonate Astringent Copper sulphate Emetic Ferrous sulphate Haematinic Zinc sulphate Astringent Bismuth subnitrate Antiseptic Lead acetate Local sedative, antiseptic  2. Non-metals : These are also used for various purposes. Agent Use Iodine (Pot. iodide) Expectorant Bromine (Pot. bromide) Sedative Hydrogen peroxide Antiseptic Sulphur Insecticide, disinfectant Carbon (charcoal) Adsorbant  Mineral Sources: i. Metallic and Non metallic sources: Iron is used in treatment of iron deficiency anaemia. Mercurial salts are used in Syphilis. Zinc is used as zinc supplement. Zinc oxide paste is used in wounds and in eczema. Iodine is antiseptic. Iodine supplements are also used Selenium is an antioxidant Gold salts are used in the treatment of rheumatoid arthritis. ii. Miscellaneous Sources Fluorine has antiseptic properties. Borax has antiseptic properties as well. Selenium as selenium sulphide is used in anti dandruff shampoos. Petroleum is used in preparation of liquid paraffin.  (II) SYNTHETIC SOURCES OF DRUGS Synthetic drugs are prepared in the laboratory with the help of inorganic and organic drugs. Today majority of drugs are obtained synthetically or semi- synthetically. Numerous drugs which were originally obtained from plants are now prepared synthetically. For example, ether and chloroform (Volatile anaesthetics), sulfonamides and quinolones (antimicrobial drugs), paracetamol (analgesic), pentobarbital and thiopental (hypnotic and parenteral anaesthetics), etc. Synthetic/ Semi synthetic Sources i. Synthetic Sources When the nucleus of the drug from natural source as well as its chemical structure is altered, we call it synthetic. Examples include Emetine Bismuth Iodide ii. Semi Synthetic Sources When the nucleus of drug obtained from natural source is retained but the chemical structure is altered, we call it semi-synthetic. Examples include Apomorphine, Diacetyl morphine, Ethinyl Estradiol, Homatropine, Ampicillin and Methyl testosterone. Most of the drugs used nowadays (such as antianxiety drugs, anti convulsant) are synthetic forms Recombinant DNA technology Recombinant DNA technology involves cleavage of DNA by enzyme restriction endonucleases. The desired gene is coupled to rapidly replicating DNA (viral, bacterial or plasmid). The new genetic combination is inserted into the bacterial cultures which allow production of vast amount of genetic material. Advantages Huge amounts of drugs can be produced. Drug can be obtained in pure form. It is less antigenic Disadvantages Well equipped lab is required. Highly trained staff is required. It is a complex and complicated technique  The following is the short description of the active constituents of crude drugs. (a) Alkaloid: These are complex, alkaline, nitrogenous compounds mostly obtained from plants and also animals. Their properties are as follows: They are nitrogenous organic compounds. They are alkaline in reaction (so named alkaloids). They combine with acids to form crystalline salts without production of water. They are readily soluble in alcohol but sparingly soluble in water. But their salts are soluble in water. A few of them are liquid, which nearly contain C, H and N only. The solid alkaloids contain oxygen in addition and are colourless crystalline in nature. Most of the alkaloids are closely related to pyridine and some may be prepared synthetically from pyridine bases. They are mostly bitter in taste. In higher concentration they are potent poisons. Their names mostly end with -ine.  Examples : Solid alkaloid : Atropine, morphine, quinine, etc. Liquid alkaloid : Arecholine, nicotine, lobeline Semi-synthetic/synthetic : Apomorphine, homatropine. Animal alkaloid : Adrenaline.  (b) Glycosides : They are mostly non-nitrogenous bodies mainly occurring in plants. They are non-nitrogenous compounds having sugar attached to non- sugar part by ether linkage. They are neutral in reaction. They mainly contain C, H and O. Some may have in addition N and few S. They do not combine with acids to form salts. They are mostly soluble in alcohol, less soluble in water and insoluble in ether. Some are highly active, while others are practically inert. These are hydrolysed by acids and liberate aglycone (non-sugar part). Their names usually end with -in. Examples : Digitoxin, scillarin, digoxin, etc.  (c) Saponins : These are plant glycosides which have distinctive property of frothing. They are a group of non-nitrogenous substances usually glycosides. They are soluble in water and form froth when shaken. On hydrolysis they split up into sugar and aglycone (sapogenin). Toxic saponins are called sapotoxins. Examples : Digitonin, senegin, glycyrrhizin, etc.  (d) Resins : These are rosin-like substances which are oxidative products of volatile oils. They are produced by some plants. They are invariably composed of a large number of substances which may be acid, alcohol or ester in chemical composition. They are secretions of plant tissues. They are bitter and amorphous solids. They are insoluble in water, but soluble in alcohol, ether, etc. They are soluble in alkalies forming non-detergent resin soaps.  Resins Examples : Resin of Jalap, podophyllin. Oleo-resins : They are natural plant exudates which are semisolid mixtures of resins and volatile oils, e.g. crude turpentine. Gum-resins : They are mixture of resins and gums, e.g. asafoetida. Balsams : They are oleoresins containing benzoic acid or cinnamic acid, e.g. benzoin, balsam of Peru, etc.  (e) Tannins: Tannins are non-nitrogenous phenol derivatives characterised by their astringent action on the mucous membrane. They mainly occur in leaves and barks of the plant. They have irritant or astringent action. They react with iron to form blue colouration. They precipitate metallic salts, alkaloids and proteins. Some are glycosides, i.e. occur in combination with sugar. Example : Tannic acid obtained from nut galls.  (f) Gums : Gums are secretory products of plants which are used as emulsifying agents for oils and, suspending agents for insoluble substances. They are amorphous, colloidal, complex polysaccharides. They dissolve in water forming viscid adhesive fluid known as mucilage. Examples : Acacia, tragacanth.  (g) Oils : Oils are obtained from vegetable, animal and mineral sources. Oils are of 3 types : - Volatile, - fixed and - mineral.  Volatile oils : These are also called as essential, ethereal, aromatic or flavouring oils as they are responsible for the aroma and odour of plants and flowers. They are composed of diverse chemical compounds such as alcohols, aldehydes, ketones, esters, sulphur compounds, etc. They are mainly present in the flowering parts of plant, leaves and fruits and give characteristic smell to plants. They are mainly obtained by a process of distillation without being decomposed. They do not form soap with alkalies.  Volatile oils They are less soluble in water but more soluble in organic solvents. Alcoholic solutions of these oils are known as essences and are used in perfumery. They do not leave a grease spot on paper. On exposure to air and light, they tend to oxidise and turn rancid. Examples : Liquid volatile oil : Eucalyptus oil, clove oil. Solid volatile oil : Camphor, menthol, thymol.  Fixed oils : They are esters of higher fatty acids (oleic, palmitic, stearic acids) and glycerines. They are obtained from fruits, seeds and some other parts of the plants. They are non-volatile and as such cannot be distilled without decomposition, so obtained by process of expression. They are insoluble (immiscible) in water, sparingly soluble in alcohol and freely soluble in ether. They are liquid at ordinary temperature. They leave a permanent grease spot on paper. They turn rancid on heating. They form soap with alkalies. Examples : Vegetable oils : Olive oil, castor oil, mustard oil. Animal oils : Cod liver oil, shark liver oil.  Fats : These are also oils containing more of palmitin and stearin making them solid at ordinary temperature, e.g. lard, lanolin, butter. Mineral oils : These are obtained by boring the earth and do not belong to organic class. Some are used in medicinal preparations and contain only C and H, e.g. liquid paraffin.  (h) Waxes : They are esters of higher fatty acids and higher monohydric alcohols. They are firmer in consistency and have higher melting points. Ex: Yellow and white bees wax.