AlkaloidsAlkaloids

DefinitionDefinitionThe term “alkaloid” (alkali-like) is The term “alkaloid” (alkali-like) is commonly used to designate basic commonly used to designate basic heterocyclic nitrogenous compounds of heterocyclic nitrogenous compounds of plant origin that are physiologically plant origin that are physiologically activeactive..

Deviation from DefinitionDeviation from Definition

Basicity: Some alkaloids are not basic e.g. Basicity: Some alkaloids are not basic e.g. Colchicine, Piperine, Quaternary alkaloids.Colchicine, Piperine, Quaternary alkaloids.

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

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

ClassificationClassification

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

Proto alkaloids:Proto alkaloids: that are derived from amino acids that are derived from amino acids and do not have nitrogen in a heterocyclic ring. and do not have nitrogen in a heterocyclic ring. e.g Ephedrinee.g Ephedrine

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

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

New DefinitionNew Definition

Alkaloids are cyclic organic compounds Alkaloids are cyclic organic compounds

containing nitrogen in a negative state containing nitrogen in a negative state of oxidation with limited distribution of oxidation with limited distribution among living organisms.among living organisms.

Distribution and occurrenceDistribution and occurrence

Rare in lower plants. Rare in lower plants. Dicots are more rich in than Monocots. Dicots are more rich in than Monocots. Families rich in Alkaloids: Apocynaceae, Families rich in Alkaloids: Apocynaceae,

Rubiaceae, Solanaceae and Papaveracea.Rubiaceae, Solanaceae and Papaveracea. Families free from Alkaloids: Rosaceae, Families free from Alkaloids: Rosaceae,

LabiataeLabiatae

Distribution in PlantDistribution in Plant

All Parts e.g. Datura.All Parts e.g. Datura. Barks e.g. CinchonaBarks e.g. Cinchona Seeds e.g. Nux vomicaSeeds e.g. Nux vomica Roots e.g. AconiteRoots e.g. Aconite Fruits e.g. Black pepperFruits e.g. Black pepper Leaves e.g. TobaccoLeaves e.g. Tobacco Latex e.g. OpiumLatex e.g. Opium

Forms of Alkaloids:Forms of Alkaloids:

Free basesFree bases Salts with Organic acids e.g. Salts with Organic acids e.g. Oxalic, acetic Oxalic, acetic

acidsacids Salts with inorganic acids e.g. Salts with inorganic acids e.g. HCl, HHCl, H22SOSO44..

Salts with special acids: e.g. Salts with special acids: e.g. Meconic acidMeconic acid in Opium, in Opium, Quinic acidQuinic acid in in CinchonaCinchona

Glycosidal form e.g. Solanine in Glycosidal form e.g. Solanine in SolanumSolanum. .

Function in PlantsFunction in Plants They may act as They may act as protectiveprotective against insects against insects

and herbivores due to their bitterness and and herbivores due to their bitterness and toxicity.toxicity.

They are, in certain cases, the final They are, in certain cases, the final products products of detoxificationof detoxification ( (waste products)waste products). .

Source of nitrogenSource of nitrogen in case of nitrogen in case of nitrogen deficiency.deficiency.

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

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

Nomenclature:Nomenclature:Trivial namesTrivial names should end by should end by "ine""ine". These names . These names

may refer to: may refer to: The The genusgenus of the plant, such as Atropine from of the plant, such as Atropine from

Atropa belladonaAtropa belladona.. The plant The plant speciesspecies, such as Cocaine from , such as Cocaine from

Erythroxylon cocaErythroxylon coca.. The The common namecommon name of the drug, such as of the drug, such as

Ergotamine from ergot.Ergotamine from ergot. The name of the The name of the discovererdiscoverer, such as Pelletierine , such as Pelletierine

that was discovered by Pelletier.that was discovered by Pelletier. The The physiological actionphysiological action, such as Emetine that , such as Emetine that

acts as emetic, Morphine acts as narcotic.acts as emetic, Morphine acts as narcotic. A prominent A prominent physical characterphysical character, such as Hygrine , such as Hygrine

that is hygroscopic.that is hygroscopic.

Prefixes and suffixesPrefixes and suffixes

Prefixes: Prefixes: "Nor-""Nor-" designates N-demethylation or N-demethoxylation, designates N-demethylation or N-demethoxylation,

e.g. norpseudoephedrine and nornicotine.e.g. norpseudoephedrine and nornicotine. "Apo-""Apo-" designates dehydration e.g. apomorphine. designates dehydration e.g. apomorphine. "Iso-, pseudo-, neo-, "Iso-, pseudo-, neo-, andand epi-" epi-" indicate different types of indicate different types of

isomers. isomers. Suffixes:Suffixes: "-dine" "-dine" designates isomerism as quinidine and designates isomerism as quinidine and

cinchonidine.cinchonidine. "-ine""-ine" indicates, in case of ergot alkaloids, a lower indicates, in case of ergot alkaloids, a lower

pharmacological activity e.g. ergotaminine is less potent pharmacological activity e.g. ergotaminine is less potent than ergotamine.than ergotamine.

Physical PropertiesPhysical PropertiesI- Condition:I- Condition: MostMost alkaloids are crystalline alkaloids are crystalline solidssolids. . Few alkaloids are amorphous solids e.g. emetine. Few alkaloids are amorphous solids e.g. emetine.

Some Some areare liquids liquids that are either: that are either: VolatileVolatile e.g. nicotine and coniine, or e.g. nicotine and coniine, or Non-volatileNon-volatile e.g. pilocarpine and e.g. pilocarpine and

hyoscine.hyoscine.

II- Color:II- Color:The The majoritymajority of alkaloids are of alkaloids are colorlesscolorless but but some some areare

coloredcolored e.g.: e.g.: Colchicine and berberine are yellow. Colchicine and berberine are yellow. Canadine is orange.Canadine is orange. The salts of sanguinarine are copper-red.The salts of sanguinarine are copper-red.

Physical PropertiesPhysical PropertiesIII- Solubility:III- Solubility: Both Both alkaloidal basesalkaloidal bases and their and their saltssalts are are soluble in alcoholsoluble in alcohol.. Generally, the Generally, the basesbases are are soluble in organic solventssoluble in organic solvents and and

insoluble in waterinsoluble in water ExceptionsExceptions:: Bases Bases soluble in watersoluble in water: caffeine, ephedrine, codeine, : caffeine, ephedrine, codeine,

colchicine, pilocarpine and quaternary ammonium bases.colchicine, pilocarpine and quaternary ammonium bases. Bases Bases insoluble or sparingly soluble in certain organic insoluble or sparingly soluble in certain organic

solventssolvents: morphine in ether, theobromine and theophylline in : morphine in ether, theobromine and theophylline in benzene.benzene.

SaltsSalts are usually are usually soluble in watersoluble in water and, and, insoluble or insoluble or sparingly soluble in organic solvents.sparingly soluble in organic solvents.

Exceptions:Exceptions: Salts Salts insoluble in waterinsoluble in water: quinine monosulphate.: quinine monosulphate. Salts Salts soluble in organic solventssoluble in organic solvents: lobeline and apoatropine : lobeline and apoatropine

hydrochlorides are soluble in chloroform.hydrochlorides are soluble in chloroform.

IV- Isomerization:IV- Isomerization:

Optically active isomers may show different Optically active isomers may show different physiological activities. physiological activities.

ll-ephedrine is 3.5 times more active than -ephedrine is 3.5 times more active than dd-ephedrine.-ephedrine. ll-ergotamine is 3-4 times more active than -ergotamine is 3-4 times more active than dd-ergotamine.-ergotamine. dd- Tubocurarine is more active than the corresponding - Tubocurarine is more active than the corresponding ll- form. - form.

Quinine (Quinine (ll-form) is antimalarial and its -form) is antimalarial and its dd- isomer - isomer quinidine is antiarrythmic. quinidine is antiarrythmic.

The The racemic (racemic (optically inactive) optically inactive) dldl-atropine is -atropine is physiologically active.physiologically active.

Chemical PropertiesChemical Properties

I- Nitrogen:I- Nitrogen: Primary amines R-NHPrimary amines R-NH2 2 e.g. Norephedrinee.g. Norephedrine

Secondary amines RSecondary amines R22-NH e.g. Ephedrine-NH e.g. Ephedrine

Tertiary amines RTertiary amines R33-N e.g. Atropine-N e.g. Atropine

Quaternary ammonium salts RQuaternary ammonium salts R44-N e.g -N e.g dd-Tubocurarine-Tubocurarine

II- Basicity:II- Basicity: RR22-NH -NH >> R-NH R-NH2 2 >> R R33-N-N

Saturated hexacyclic amines is more basic than aromatic Saturated hexacyclic amines is more basic than aromatic amines.amines.

According to basicity Alkaloids are classified According to basicity Alkaloids are classified into:into:

Weak bases e.g. CaffeineWeak bases e.g. Caffeine Strong bases e.g. AtropineStrong bases e.g. Atropine Amphoteric Amphoteric

* Phenolic Alkaloids e.g. Morphine * Phenolic Alkaloids e.g. Morphine *Alkaloids with Carboxylic groups e.g. Narceine*Alkaloids with Carboxylic groups e.g. Narceine

Neutral alkaloids e.g. ColchicineNeutral alkaloids e.g. Colchicine

III- Oxygen:III- Oxygen:

Most alkaloids contain Oxygen and are Most alkaloids contain Oxygen and are solid in nature e.g. Atropine.solid in nature e.g. Atropine.

Some alkaloids are free from Oxygen and Some alkaloids are free from Oxygen and are mostly liquids e.g. Nicotine, Coniine.are mostly liquids e.g. Nicotine, Coniine.

IV- Stability:IV- Stability:

Effect of heatEffect of heat::

Alkaloids are decomposed by heat, except Alkaloids are decomposed by heat, except StrychnineStrychnine and and caffeinecaffeine ( (sublimablesublimable).).

Reaction with acids:Reaction with acids: 1- Salt formation.1- Salt formation.

2- Dil acids hydrolyze Ester Alkaloids e.g. Atropine2- Dil acids hydrolyze Ester Alkaloids e.g. Atropine

3- Conc. acids may cause:3- Conc. acids may cause:

Dehydration:Dehydration:

Atropine → ApoatropineAtropine → Apoatropine

Morphine → ApomorphineMorphine → Apomorphine Demethoxylation:Demethoxylation:

e.g. Codeinee.g. Codeine

Effect of Alkalies:Effect of Alkalies:1- Dil alkalis1- Dil alkalis liberate most alkaloids from their salts liberate most alkaloids from their salts

e.g. NH3. e.g. NH3. 2- They may cause isomerization (racemization) of 2- They may cause isomerization (racemization) of

alkaloid as the conversion of hyoscyamine to alkaloid as the conversion of hyoscyamine to atropine.atropine.

3- They also can 3- They also can form salts with alkaloids form salts with alkaloids containing a carboxylic groupcontaining a carboxylic group e.g. narceine. e.g. narceine.

4- Strong alkalis:4- Strong alkalis: such as aqueous NaOH and KOH such as aqueous NaOH and KOH form salts with phenolic alkaloids.form salts with phenolic alkaloids.

5- Strong alkalis cause hydrolysis of Ester 5- Strong alkalis cause hydrolysis of Ester alkaloidsalkaloids (e.g. atropine, cocaine and (e.g. atropine, cocaine and physostigmine) and physostigmine) and Amide alkaloidsAmide alkaloids ( colchicines).( colchicines).

66- Strong alkalis cause opening of lactone ring.- Strong alkalis cause opening of lactone ring.

Effect of light and OxygenEffect of light and Oxygen

Eserine RubreserineOxygen

Alkaline solutions

Reserpine Decomposition

Ergot Alkaloids Lumi Alkaloids(Inactive)

Qualitative test for AlkaloidsQualitative test for Alkaloids

Precipitation Reagents:Precipitation Reagents:

They are used to:They are used to:

1- Indicate the absence or presence of 1- Indicate the absence or presence of AlkaloidsAlkaloids

2- Test for complete of extraction2- Test for complete of extraction

Disadvantages:Disadvantages: Some non alkaloids interfere Some non alkaloids interfere such as Proteins, lactones, coumarinssuch as Proteins, lactones, coumarins

Classification of Alkaloidal precipitating agents:Classification of Alkaloidal precipitating agents:1- Reagents that form double salts:1- Reagents that form double salts:

a- Mayer’s Reagent: Potassium Mercuric Iodide.a- Mayer’s Reagent: Potassium Mercuric Iodide.

b- Dragendorff’s Reagents: Potassium Iodobismethate.b- Dragendorff’s Reagents: Potassium Iodobismethate.

c- Gold Chloride.c- Gold Chloride.

2- Reagents Containing Halogens:2- Reagents Containing Halogens:

a- Wagner’s Reagent: Iodine/ Potassium Iodide.a- Wagner’s Reagent: Iodine/ Potassium Iodide.

3-Organic Acids:3-Organic Acids:a- Hager’s Reagent: Picric Acida- Hager’s Reagent: Picric Acid

b- Tannic Acid.b- Tannic Acid.

4- Oxygenated High Molecular Weight Acids:4- Oxygenated High Molecular Weight Acids:a- Phosphomolybdic acida- Phosphomolybdic acid

b- Phosphotungestic acidb- Phosphotungestic acid

c- Silicotungestic Acidc- Silicotungestic Acid

Colour Reagents:Colour Reagents:

1- Froehd’s Reagent: 1- Froehd’s Reagent: Phosphomolybdic acidPhosphomolybdic acid

2- Marqui’s Reagent:2- Marqui’s Reagent: Formaldehyde/ Conc. H Formaldehyde/ Conc. H22SOSO44

3- Mandalin’s Reagent: 3- Mandalin’s Reagent: Sulphovanidic acidSulphovanidic acid

4- Erdmann’s Reagent:4- Erdmann’s Reagent: Conc. HNO Conc. HNO33/Conc. H/Conc. H22SOSO44

5- 5- Mecke's Reagent:Mecke's Reagent: Selenious acid / conc. H Selenious acid / conc. H22SOSO44

6- 6- Shaer's Reagent:Shaer's Reagent: Hydrogen peroxide / conc. H Hydrogen peroxide / conc. H22SOSO44

7- 7- Rosenthaler's Reagent:Rosenthaler's Reagent: Potassium arsenate / conc. HPotassium arsenate / conc. H22SOSO44

8- 8- Conc. HNOConc. HNO33

Extraction, Purification and Isolation of Extraction, Purification and Isolation of Alkaloids from Powdered plantsAlkaloids from Powdered plants

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

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

Method II:Method II: The powdered material is extracted with The powdered material is extracted with water or aqueous water or aqueous

alcoholalcohol containing containing dilute aciddilute acid. . AlkaloidsAlkaloids are extracted as are extracted as their their saltssalts together with accompanying together with accompanying soluble impuritiessoluble impurities..

Method III:Method III: The powder is extracted with water soluble organic solvents The powder is extracted with water soluble organic solvents

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

Plant material and solvent

Extract

Concentration

Acidified Extract (Alk. as salts)

Organic solvent dissove Impurities

Acidification

Alkalinization

Alkaline aqueous layer

Organic solvent dissove Alkaloids

Liberation of the free basesLiberation of the free bases

Alkalis are used to liberate free bases. Alkalis must be strong Alkalis are used to liberate free bases. Alkalis must be strong

enough to liberate free bases. However, choice of strong enough to liberate free bases. However, choice of strong

alkalis must be avoided in some cases:alkalis must be avoided in some cases:

1- Ester Alkaloids e.g. Solanaceous Alkaloids1- Ester Alkaloids e.g. Solanaceous Alkaloids

2- Amide Alkaloids e.g. Colchicine2- Amide Alkaloids e.g. Colchicine

3- Phenolic Alkaloids e.g. Morphine3- Phenolic Alkaloids e.g. Morphine

4- Lactone Alkaloids e.g. Pilocarpine4- Lactone Alkaloids e.g. Pilocarpine

5- Fatty Drugs due to saponification and emulsion formation. 5- Fatty Drugs due to saponification and emulsion formation.

NHNH44OH:OH:

Most widely used due to many Most widely used due to many advantages:advantages:1- Strong enough to liberate most of alkaloids 1- Strong enough to liberate most of alkaloids from their salts.from their salts.

2- Milder than fixed alkalis so more safe.2- Milder than fixed alkalis so more safe.

3- Volatile so easy to get rid of it.3- Volatile so easy to get rid of it.

Other Alkalis:Other Alkalis:NaNa22COCO33, NaHCO, NaHCO33, Ca(OH), Ca(OH)22, MgO., MgO.

Extraction of the free bases:Extraction of the free bases: CHClCHCl33::

Strong solvent can extract most of the Strong solvent can extract most of the alkaloids.alkaloids.

Extracts contain more impurities.Extracts contain more impurities.

Carcinogenic.Carcinogenic.

Ether:Ether:Gives cleaner Extract but have some Gives cleaner Extract but have some disadvantages:disadvantages:

1- High volatility1- High volatility

2- Peroxide formation2- Peroxide formation

3- High water miscibility3- High water miscibility

Volatile AlkaloidsVolatile Alkaloids

The best way for their extraction is steam The best way for their extraction is steam distillation.distillation.

Plant material + water + Fixed alkaliPlant material + water + Fixed alkali HeatHeat

steam containsteam contain alkaloids received in alkaloids received in

acidic sloution.acidic sloution.

Purification of the Crude Alkaloidal Purification of the Crude Alkaloidal Fractions:Fractions:

Repeated Acid-Base procedures:Repeated Acid-Base procedures:Render extract Render extract AcidicAcidic, extract with , extract with organic solventorganic solvent (dissolve non alkaloidal (dissolve non alkaloidal impurities), impurities), AlkalinizeAlkalinize and extract again and extract again with with organic solventsorganic solvents (Dissolve (Dissolve Alkaloids).Alkaloids).

Precipitation with alkaloidal precipitating Precipitation with alkaloidal precipitating agent.agent.

Convert to crystalline salts.Convert to crystalline salts.

Separation of Alkaloidal Mixtures:Separation of Alkaloidal Mixtures:

Fractional CrystallizationFractional Crystallization

Ephedrine & Pseudoephedrine Oxalates

Crystallization from water

Ephedrine OxalateCrystals

Pseudoephedrine OxalateSolution

Atropine & Hyoscyamineine Oxalates

Crystallization from Acetone/Ether

Atropine OxalateCrystals

Hyoscyamine OxalateSolution

Preparation of Derivatives:Preparation of Derivatives:

Separation of Primary, Secondary and Tertiary Alkaloids.Separation of Primary, Secondary and Tertiary Alkaloids.

Mixture + p-toluenesulphonyl chloride

Add HCl and filter

Filtrate

tertiary alkaloids as salt(no reaction with reagent

Precipitate

SCl

O

O

1ry alk derivative 2ry alk derivative

SR-HN

O

OSR-N

O

O

R

SR-N

O

OH

keto form

enol form soluble in alkalis

acidic hydrogeninsoluble in alkalis

NaOH, filter

Filtrate Precipitate

1ry alk derivative 2ry alk derivative

Fractional Liberation:Fractional Liberation:

Atropine & Hyoscyamine & Hyoscine the form of HCl salts

1- Alkalinize by NaHCO3 pH 7.52- Extract with Ether

EtherHyoscine free base

(pKa = 6.2)

Aqueous layerAtropine & Hyoscyamine HCl

(pKa = 9.3)

Fractional Distillation:Fractional Distillation:

e.g. Separation of Nicotine and Anabasine e.g. Separation of Nicotine and Anabasine

Chromatographic Separation.Chromatographic Separation.

Identification of AlkaloidsIdentification of Alkaloids

Melting pointMelting point Colour testColour test Optical RotationOptical Rotation Microcrystal testMicrocrystal test HPLC, GC, GC-MSHPLC, GC, GC-MS UV, IR, NMR, MS.UV, IR, NMR, MS.

Quantitative Determination of Alkaloids:Quantitative Determination of Alkaloids:

Volumetric methods:Volumetric methods: These are based on reaction of alkaloidal bases with These are based on reaction of alkaloidal bases with

acids (Acid-Base titration).acids (Acid-Base titration).They include:They include:

Aqueous titration:Aqueous titration: This is carried by either: This is carried by either:1- 1- Direct titrationDirect titration of the alcoholic solution of the of the alcoholic solution of the

alkaloidal residue with standard acid, oralkaloidal residue with standard acid, or2- 2- Back titrationBack titration by dissolving the residue in a by dissolving the residue in a

known amount of standard acid and back titration of known amount of standard acid and back titration of residual acid against standard alkali.residual acid against standard alkali.

Non-aqueous titration:Non-aqueous titration: This method is suitable for This method is suitable for determination of weak bases e.g. Caffeine.determination of weak bases e.g. Caffeine.

Gravimetric methods:Gravimetric methods: These methods are recommended for determination of:These methods are recommended for determination of:

1- Very weak bases1- Very weak bases which can not be determined by which can not be determined by volumetric methods e.g. caffeine and colchicine.volumetric methods e.g. caffeine and colchicine.2- Mixtures of alkaloids2- Mixtures of alkaloids that are obtained from the same that are obtained from the same plant but differ greatly in their molecular weight e.g. plant but differ greatly in their molecular weight e.g. Cinchona and Rawolfia alkaloids.Cinchona and Rawolfia alkaloids.

They can be performed by either:They can be performed by either:1- Direct Weighing of the alkaloidal mixtures1- Direct Weighing of the alkaloidal mixtures2- Precipitation of the total alkaloids and determination of 2- Precipitation of the total alkaloids and determination of the weight of the precipitate obtained.the weight of the precipitate obtained.

The major The major drawbacksdrawbacks of the gravimetric methods are: of the gravimetric methods are: 1- They are insensitive to microamounts of alkaloids.1- They are insensitive to microamounts of alkaloids.2- They could not be applied in case of thermolabile and 2- They could not be applied in case of thermolabile and volatile alkaloids.volatile alkaloids.3- Lipophilic impurities in the residue are calculated as 3- Lipophilic impurities in the residue are calculated as alkaloids.alkaloids.

Colourimetric Method:Colourimetric Method:

e.g. Morphine + NaNOe.g. Morphine + NaNO22/HCl/HCl

Ergot + p-dimethylaminobenzaldehydeErgot + p-dimethylaminobenzaldehyde

Spectrophotometric Methods.Spectrophotometric Methods. Polarimetric Method.Polarimetric Method. Fluorimetric Method.Fluorimetric Method. Chromatographic MethodsChromatographic Methods

Classification of AlkaloidsClassification of Alkaloids Biogenetic.Biogenetic.

Based on the biogenetic pathway that form the alkaloids.Based on the biogenetic pathway that form the alkaloids.

Botanical Source.Botanical Source.

According to the plant source of alkaloids.According to the plant source of alkaloids.

Type of Amines.Type of Amines.Primary, Secondary, Tertiary alkaloids.Primary, Secondary, Tertiary alkaloids.

Basic Chemical SkeletonBasic Chemical Skeleton

Phenylalkylamines:Phenylalkylamines:

e.g. Ephedrinee.g. Ephedrine

Pyridine and piperidinePyridine and piperidine

e.g. lobeline, nicotinee.g. lobeline, nicotine

TropaneTropane

e.g. Atropine.e.g. Atropine.

CH2 CH CH3

NH2

N NH

NCH3 OH

QuinolineQuinoline

e.g.quinine and quinidinee.g.quinine and quinidine

Isoquinoline Isoquinoline

e.g. papaverinee.g. papaverine

Phenantheren Phenantheren

e.g. Morphinee.g. Morphine

N

N

Indole Indole

e.g.ergometrinee.g.ergometrine

Imidazole Imidazole

e.g. pilocarpinee.g. pilocarpine

Purine Purine

e.g. caffeinee.g. caffeine

NH

N

N

N

N N

N

H

Purine

1

2

34

56 7

8

9

Steroidal Steroidal e.g. Solanum and e.g. Solanum and VeratrumVeratrum

alkaloidsalkaloids

TerpenoidTerpenoide.g. Taxole.g. Taxol