ALKALOIDS - of alkaloid ... *Pre-cursors to pyrrolidien, piperridine tropane alkaloids

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Text of ALKALOIDS - of alkaloid ... *Pre-cursors to pyrrolidien, piperridine tropane alkaloids


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    Learning Objective

    Definition of alkaloids Classification of alkaloid Distribution, localization and function Uses Physical characters Methods of preparation Quality control Storage Chemistry Classification Alkaloids containing drugs from medicinal plants and their uses

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    Learning outcomes

    The students will be able to :

    1. recognize the alkaloids and molecular structure of alkaloids


    2. apply different techniques for isolation, extraction, characterization

    and purification of alkaloids

    3. describe metabolic steps and regulation of the biosynthesis of

    organic compounds.

    4. Identify plants containing therapeutically active aromatic


    5. describe different alkaloids containing medicinal plants and their

    therapeutically uses.

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  • Definition: the term alkaloid (alkali-like) is commonly used to designate basic heterocyclic nitrogenous compounds of plant origin that are physiologically active.

  • Deviation from Definition

    Basicity: Some alkaloids are not basic e.g.

    Colchicine, Piperine, Quaternary alkaloids.

    Nitrogen: The nitrogen in some alkaloids is not in a heterocyclic ring e.g. Ephedrine, Colchicine, Mescaline.

    Plant Origine: Some alkaloids are derived from Bacteria, Fungi, Insects, Frogs, Animals.

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  • Classification of Alkaloids

    True (Typical) alkaloids that are derived from amino acids and have nitrogen in a heterocyclic ring. e.g Atropine

    Protoalkaloids that are derived from amino acids and do not have nitrogen in a heterocyclic ring. e.g Ephedrine

    Pseudo alkaloids that are not derived from amino acids but have nitrogen in a heterocyclic ring. e.g Caffeine

    False alkaloids are non alkaloids give false positive reaction with alkaloidal reagents.

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  • Distribution and occurrence

    Rare in lower plants.

    Dicots are more rich in alkaloids than


    Families rich in Alkaloids: Apocynaceae,

    Rubiaceae, Solanaceae and Papaveracea.

    Families free from Alkaloids: Rosaceae,


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  • All Parts e.g. Datura.

    Barks e.g. Cinchona

    Seeds e.g. Nux vomica

    Roots e.g. Aconite

    Fruits e.g. Black pepper

    Leaves e.g. Tobacco

    Latex e.g. Opium

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  • They may act as protective against insects and herbivores due to their bitterness and toxicity.

    Source of nitrogen in case of nitrogen deficiency.

    They, sometimes, act as growth regulators in certain metabolic systems.

    They may be utilized as a source of energy in case of deficiency in carbon dioxide assimilation.

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  • Condition

    Most alkaloids are crystalline solids.

    Few alkaloids are amorphous solids e.g. emetine.

    Some are liquids that are either: Volatile e.g. nicotine and coniine Non-volatile e.g. pilocarpine and hyoscine. MW: 100 900 amu 26-Jul-17 11

  • Color

    The majority of alkaloids are colorless but some are colored


    Colchicine and berberine are yellow.

    Canadine is orange.

    The salts of sanguinarine are copper-red.


    Both alkaloidal bases and their salts are soluble in alcohol.

    Generally, the bases are soluble in organic solvents and

    insoluble in water

    Physical Properties

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  • Exceptions

    Bases soluble in water: caffeine, ephedrine, codeine,

    colchicine, pilocarpine and quaternary ammonium


    Bases insoluble or sparingly soluble in certain organic

    solvents: morphine in ether, theobromine and

    theophylline in benzene.

    Salts are usually soluble in water and, insoluble or

    sparingly soluble in organic solvents.

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  • Weak bases e.g. Caffeine

    Strong bases e.g. Atropine


    * Phenolic Alkaloids e.g. Morphine

    *Alkaloids with Carboxylic groups e.g. Narceine

    Neutral alkaloids e.g. Colchicine

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  • Stability Effect of heat

    Alkaloids are decomposed by heat, except Strychnine and caffeine (sublimable).

    Chemical test:

    Mayers Reagent: Cream color precipitate

    Dragendorffs Reagents: Orange color precipitate

    Wagners Reagent: Reddish brown color precipitate

    Hagers Reagent: Reddish brown color precipitate

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  • Extraction is based on the basicity of alkaloids and on the

    fact that they normally occur in plants as salts (i.e.: on

    the solubility of bases and salts in water and organic


    Herbs often contain other materials which can interfere

    with extraction such as large amounts of fat, waxes,

    terpenes, pigments and other lipophilic substances (e.g

    by forming emulsions) avoided by defatting the crushed

    herb (using petroleum ether and hexane)

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  • Extraction and purification Method I: The powder is treated with alkalis to liberates the free

    bases that can then be extracted with water immiscible organic solvents.

    Method II: The powdered material is extracted with water or

    aqueous alcohol containing dilute acid. Alkaloids are extracted as their salts together with accompanying soluble impurities.

    Method III: The powder is extracted with water soluble organic

    solvents such as MeOH or EtOH which are good solvents for both salts and free bases.

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  • Extraction of the free bases:


    Strong solvent can extract most of the alkaloids.

    Extracts contain more impurities.



    Gives cleaner Extract but have some disadvantages:

    High volatility

    Peroxide formation

    High water miscibility

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  • Aliphatic AAs ornithine & lysine *Pre-cursors to pyrrolidien, piperridine & tropane alkaloids

    Aromatic AA Phenylalanine, tyrosine, tryptophane

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  • Derived from tropine and consist of mandelic, tropic or benzoic acid esters of tropine.

    Are very closely related to each other

    All have pronounced physiological actions.

    Natural alkaloids include Hyoscyamine Hyoscine Atropine Cocaine

    The above mentioned alkaloids occur within the Solanaceae family (except cocaine from Erythroxylaceae family)

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  • Have the same structure differ only in their optical activity.

    Also have different physiological actions

    Atropine deadly nightshade, Atropa belladonna: to dilates eye pupils, decreases sweating, produces stomach acid and saliva & relaxes smooth muscle (asthma and colic).

    Hyoscine black henbane, Hyoscyamus niger: Limited influence on the CNS. Sedative

    Cocaine: Narcotic properties & local anaesthetic action (e.g. used in eye drops).

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  • Hyoscine

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  • Definition: Stramonium Leaf consists of the dried leaves or dried leaves and flowering tops of Datura stramonium. The drug should contain at least 0.25% alkaloids calculated as hyoscyamine.

    Common names: Stramonium leaf, Thornapple, Jimson or Jamestown weed

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  • Main (Tropane) Alkaloids 1. Hyoscyamine 2. Hyoscine (2:1)

    Younger plants: hyoscine predominant alkaloid Also contains Atropine

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  • ALLIED DRUGS Datura innoxia

    Datura metel (dried leaves are also curled and twisted like D. stramonium), but are browner in colour.

    ADULTERANTS Xanthium, Carthamus and Chenopodium leaves (easily distinguished from original herb)

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  • Atropine & Hyoscine: used in opthalmic practice to dilate the pupil of the eye.

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  • Definition: Hyoscyamus leaf consists of the dried leaves or dried leaves and flowering tops of Hyoscyamus niger. It should contain at least 0.05% alkaloids hyoscyamine.

    Common names:


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  • Tropane Alkaloids



    Hyoscine (main constituent)

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  • 1. Hyoscyamus albus (bottom left).

    2. Hyosycamus muticus (top)

    3. Hyoscyamus pusillus

    4. Hyoscyamus aureus

    5. Hyoscyamus reticulatus

    (Indian henbane bottom right)

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  • Resembles belladonna and stramonium in action only weaker.

    Higher hyoscine content

    Used to relieve spasm of the urinary tract

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  • Definition: Belladonna herb consists of the dried leaves and flowering tops of Atropa belladonna, containing at least 0.3% alkaloids (hyoscyamine).

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  • Main (Tropane) alkaloid


    Also contains


    Calcium oxalate

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  • Used as a sedative

    To stop bronchial spasms in asthma and whooping cough, and as a cold and hay fever remedy. It is also used for Parkinson's disease, colic, motion sickness

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