Active Principles & Sources of Drugs
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General Pharmacology
Muhammad Faisal Nadeem
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DRUGS DRUGS
The word drug is derived from the French word drogue, a dry herb, it is defined as any substance used for the purpose of diagnosis prevention, relief or cure of a disease . In man or animals use of drug depends upon no. of factors .
1. Source 2. Chemistry 3. Absorption 4. Metabolism 5. Excretion 6. Mechanism of action 7. Side effects/ toxicity 8. Margin of safety 9. Uses
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Nomenclature of the drugs 1. Chemical names: Indicates molecular structure . It is complex
and not used e.g. Acetyl-p-aminophenal.
2. Official approved name : It is the abbreviated form of chemical name used in pharmacopeia and named officially e.g. Paracetamol.
3. Proprietory name (brand / trade name) name given by the company which markets the drug . It is a commercial property of a pharmaceutical company.
To avoid confusion drugs should be prescribed by their approved name e.g
1.Chemical name: Acetylp-aminophenal
2.Official name : Paracetamol
3.Brand name : Panadol , Calpol
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Origin of Drugs / Bioactive Compounds: History
Before 1800: Plants, plant extracts, inorganic material
1805: Morphine isolated from opium (sructure proposed 1935, prooved by synth. 1952)
1828: First organic synthesis (urea)
1840-1850: First synthesized org. compds used in medicine: CHCl3, Et2O anestechia)Ex of early synthetic drugs:
Choral hydrate (sleeping pill) 1869Acetyl salicylic acid synth 1853Phenazone synth 1884Benzocaine 1902Prontocil 1932
Ex of early isolated nat. prod.Quinine ca 1825Digitoxin 1841 (structure
1928)Salicylic acid, antipyretic 1875Cocaine isol. 1860, local
anestethic 1884Benzylpenicillin 1941
Traditional medicineScreeningSerendipity
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Active Principles Of Crude Drugs Definition
The chemical constituents present in crude animal/vegetable preparations, responsible for their biological activity are called active principles.
Active Principles have been purified and synthetic/ semi- synthetic derivatives can be prepared and used in Therapeutics.
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The Aims of Isolating Active Principles
• 1. Identification of the active ingredient(s).
• 2. Analysis of the biological effects (pharmacodynamics) of individual ingredients and of their fate in the body (pharmacokinetics).
• 3. Ensuring a precise and constant dosage in the therapeutic use of chemically pure constituents.
• 4. The possibility of chemical synthesis, which would afford independence from limited natural supplies and create conditions for the analysis of structure–activity relationships.
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Sources of Drugs
Drugs may be synthesized within the body (eg, hormones) or may be chemicals not synthesized in the body, ie, xenobiotics (from Gr xenos "stranger"). Poisons are drugs. Toxins are usually defined as poisons of biologic origin.
• Drugs may be solids, liquids or gaseous.• Many drugs are weak acids or bases• Majority of drugs have molecular weights between 100
and 1000• chirality (stereoisomerism)
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Drugs may be obtained from: • Plants • Animals• Mineral / Earth • Synthetic / Semi-synthetic sources• Microbiological sources• Recombinant DNA technology /Genetic engineering.
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Plant / Vegetable Sources
• The oldest natural source. Even now some drugs are obtained from the plant source.
• Drugs can be obtained from all parts of the plants:
– Leaves: Digitalis purpurae ---- Digoxin
– Flowers: Papaver Somnipherum --------- Morphine
– Fruits : Senna pod --------------------- Anthracine
– Seeds: Nuxvomica seeds-------strychnine.
– Roots : Ipecacuanha root ------- Emetine
– Barks: Cinchona bark ------- Quinine
– Stem: Chondrodendron ----- d-tubocurarine
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Animal Sources
• Various organs & tissue of animals are used as source of drug.
• Active principles of animal drugs are proteins, oils, fat, enzymes and hormones.
– Pancreas ………………………... Insulin
– Cod liver ……… Cod liver oil (contains Vit A & D)
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Mineral / Earth Sources
Many drugs are mineral substances & their compounds.• Metals: Iron , Zinc, Gold salts• Non - metallic element: Iodine• Miscellaneous: Flourine, Selenium
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Synthetic & Semisynthetic Sources
• The drugs are prepared in pharmaceutical laboratories. They may be organic or inorganic compounds or combination of both.
• 90% drugs in use are prepared synthetically. – Co-trimoxazole.– Diazepam.– Diacetyl morphine.– Ethinyl estradiol.
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Microbiological Sources
These are prepared from bacteria & moulds.
Examples:• Antibiotics: Penicillin , Erythromycin• Vitamins
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Recombinant DNA Technology /
Genetic engineering
The new technique for preparing certain drugs e.g. Human insulin insulin analog , Erythropoietin.
• Human Insulin & insulin analogs may be prepared by inserting human or modified pro-insulin gene into E-coli or yeast & treating the extracted pro-insulin to form the insulin or insulin analog molecules.
Advantages:
• Mass production.
• Cost effective
• Less immunological reactions.
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Important active principles
• Alkaloids• Glycosides• Saponins• Fixed oils• Volatile oils • Fats• Waxes• Gums• Resins• Oleoresins• Gum resins• Balsams• Tannins • Neutral principles
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Alkaloids:
The characteristics are:• Nitrogenous compounds of complex structure.• Found in plants, more than one alkaloids may be
present in one plant.• Intensely bitter.• Insoluble in water, soluble in alcohol.• Very active biologically, alkaline in reaction.• Form salts with acids which are water soluble.• Mostly solids, only a few are liquids.• English names end in ----“INE”.
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Examples:
Solid Alkaloids: • Morphine, Papavarine• Atropine , Hyoscine• Quinine• Ephedrine• Strychnine
Liquid Alkaloids:• Nicotine , Pilocarpine , Lobeline
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Glycosides:
The characteristics are:
1. Non nitrogenous, containing carbon, hydrogen & oxygen
2. Complex structure & very active biologically
3. Found in plants
4. Hydrolyzed by acid / enzymes into:• Sugar component or Glycone ----
Mainly determines pharmacokinetics• Non-Sugar component or Aglycone/Genin - --
Pharmacologically active
5. When sugar component is glucose, it is called glucoside
6. English names end in letter “IN”
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Examples:Cardiac Glycosides:• Digoxin• Digitoxin• Gitoxin• Gitalin• Strophanthin
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Saponins:
• These resemble glycosides• Neutral in reaction• Found in plants• Act as emulsifying agents• Form clear solution with water which forms froths on
shaking • They are toxic • May cause haemolysis of RBCS• Examples: Senegin, Quillia sapotoxin
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Fixed Oils:
obtained from various plants or animals.• Esters of higher fatty acid (Oleic/Palmitic/ Stearic
acids) .• Insoluble in water , soluble in ether, chloroform,
alcohol. • Bland + non irritating .• Leave greasy mark on paper.• Decompose on distillation .• Form soaps with alkalies.• Used as: Nutrient , Emollient , Purgative.Examples: Castor oil , Cod liver oil , Olive oil.
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Volatile Oils: (Essential Oils / Ethereal Oil)
Obtained from various parts of plants by distillation processes & are highly aromatic.
• Mostly contain liquid hydrocarbons which are monoturpenes
In addition most contain oxidized hydrocarbons.• They are usually crystalline solids, called stearoptenes • Highly aromatic, slightly water soluble – impart smell & taste.• Used as:
– Carminative e.g. cardamon oil– Diuretic e.g. oil of sandal wood– Antiseptic e.g. clove oil– Counter Irritant e.g. turpentine oil– Expectorant e.g. balsam of tolu
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Examples
Usually Solids:• Camphor• Thymol• Menthol
Some Liquids: Eucalyptol
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Fats:
• Fixed oils solid at room temperature• Natural ester of glycerol & fatty acids. All the
three OH groups of glycerol are esterified, so called Triglycerides
• Source Plants
Animals• Examples: Theobroma (cocoa butter) , Wool fat
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Waxes:
• Esters of fatty acids with monohydric alcohols• Complex mixtures• Used in ointments & other topical preparations
used on skin.
Examples: White bee’s wax (cera alba)
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Gums:
• Plant exudations• Carbohydrate in nature Starch
Cellulose• Amorphous, Transparent• Form viscous solution with water – Mucilage• Used as suspending/emulsifying agents in
preparation of suspensions & emulsions. • Examples: Gum Acacia, Gum Tragacanth
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Resins:
• Solid & brittle substances, produced by oxidation of volatile oils
• Form soap with alkali• Soluble in alcohol
Examples: Colophony.
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Tannins:
• Non-Nitrogenous compounds .• Precipitated by metallic salts or alkaloids.• Astringent action on mucosa.• Produce blue inky color with iron.• Some are hydrolyzed to tannic acid.
Neutral Principles:• Do not conform to any special group .• Examples: Santonin, Bitter principles .
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Sources of Drugs• PlantsExample Trade Name
ClassificationChinchona BarkQuinidine Antiarrhythmic
Purple Foxglove Digitalis Cardiotonic
Poppy Plant Paregoric, Antidiarrheal,(Opium) Morphine, Analgesic,
Codeine Analgesic, Antitussive
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Sources of Drugs• MineralsExample Trade Name ClassificationMagnesium Milk of Magnesia Antacid, Laxative
Zinc Zinc Oxide Oint. Sunscreen, Skin Protectant
Gold Solganal, Auranofin Anti-inflammatory;
Used in tx of Rheumatoid
Arthritis
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• AnimalsExample Trade Name
ClassificationPancreas of Cow, Insulin; regular, AntidiabeticHog NPH, PZI Hormone
Stomach of Cow, Pepsin DigestiveHog Hormone
Thyroid Gland Thyroid, USP HormoneOf Animals
Sources of Drugs
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Sources of Drugs• SyntheticExample Trade Name
ClassificationMeperidine Demerol Analgesic
Diphenoxylate Lomotil Antidiarrheal
Co-TrimoxazoleSeptran Anti-Infective Sulfonamide; Used in the treatment of UTI’s
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Doses of Drugs
DoseMinimum doseMaximum doseDaily doseTotal doseSingle doseLoading doseMaintenance doseMedian lethal doseMedian effective doseTherapeutic indexToxic dose & fatal dose