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SIGNIFICANCE OF ALKALOIDS IN

CHEMOTAXONOMY

Supervised by- Presented by-Dr. Annie Shirwaikar Chandresh Dwivedi

Professor, M.Pharm-I

Roll no. 080605022

Dept. of Pharmacognosy.

MANIPAL COLLEGE OF

PHARMACEUTICAL SCIENCES,

MANIPAL

KARNATAKA.

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Introduction of chemotaxonomy

Principles of chemotaxonomy

Criteria for using alkaloids in taxonomy

Use of alkaloids in taxonomy

References

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Introduction

Chemotaxonomy is an attempt to classify plants on

basis of their chemical constituents.

y W

hen properly applied, it is undoubtedly more usefulthan much subjective morphology (e.g. leaf shape).

Chemotaxonomy incorporates the principles &

procedures involved in the use of chemical evidence

for classificatory purpose.

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Principles of chemotaxonomy

y Chemical classification of plants is based on their

chemical constitutions; i.e. on their molecular

characteristics.

y The same type of metabolites can be the product of two

quite different pathways.

y

Different plants sometimes contain secondaryconstituents belonging to different classes of

compound but biosynthetically appear to be same.

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y Chemotaxonomic studies include the investigation of

the pattern of compound occurring in the plant andpreferentially in all various individual parts of plantsuch as the bark , wood, leaves , root, cuticles and seed.

y Such integrated investigations are necessary in orderto obtain really convincing evidence for therelationship of plants.

y Before any important conclusions are drawn about the

presence or absence of a particular compoundadequate sampling of a large number of members ofthe species at different stages of development andgrowing in different environment should be made.

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Alkaloids

y

Alkaloids are compounds, containing heterocyclic nitrogen, basiccharacter and complex molecular structure. Such compounds arerestricted to plant kingdom.

True alkaloids have a nitrogen-containing nucleus derived frombiogenetic amine.

Proto alkaloids derived from amino acids, but lack aheterocyclic ring.

y Natural protoalkaloids are usually simple amines e.g. ephedrine ,mescaline.

y

Some times they may be precursor of true alkaloids.

Pseudo alkaloids biologically unrelated to amino acids.

y Most of them derived from- terpenes, sterols , nicotinic acid orpurines.

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Occurrence and Distribution

y Higher plants particularly in the dicotyledons ,abundance inthe Angiosperms families Apocynaceae, Papaveraceae,Ranculaceae, Rubiaceae, Rutaceae, Solanaceae, but lessfrequent in lower plants and fungi.

y In plants, alkaloids, due to their basic nature, generally existas a salt of organic acid like, oxalic acid, citric acid, malicacid,, tartaric acid, tannic acid etc.

y Some alkaloids like narceine and nicotine are occurring free

in nature.y A few alkaloids occur as glycoside of sugars like glucose,

rhamnose, and galactose. E.g. alkaloids of solanum andveratrum groups as amides (Piperine), as esters (Atropine,Cocaine) of organic acid.

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Criteria for using Alkaloids in taxonomy

A. Definition of alkaloids

B. Definition of alkaloid plants

C. The type of alkaloids that can be distinguished

D.Homologous and analogous characters

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A. Definition- (Alkaloids proper)

y Alkaloids are more or less toxic substances which actprimarily on CNS. They have a basic character, contain

heterocyclic nitrogen, and are synthesized in plants

from amino acid and or their immediate derivatives .

They are of limited distribution in plant kingdom.

y But such definition excludes a number of nitrogen

containing plant constituents, which are normally

thought as alkaloids.

E.g. Biological amines like

Ephedrine,Hardenine,Betain ,Cholin, Muscarine

y All such alkaloids are separately referred as

protoalkaloids or biological aminesoramino

alkaloids.

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y But when protoalkaloids and true alkaloids occur in

same genus or family, both are usually classified asalkaloids.

y Ex. Hardenine, Mescaline in cactaceae family.

y Another group of nitrogen compounds that fall outside

our definition of alkaloids aremono, sesqui,di-

terpenes, steroids, nicotinic acid, purines.

y These can also be classified according to precursor onwhich they are based and collectively called as pseudo

alkaloids or alkaloid imperfecta.

Ex . Conessine, Caffeine.

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B. Definition of alkaloid plantsy There is no sharp dividing line between alkaloids

containing plants and alkaloids free plants.

y From practical point of view, we can define lower limit

as 0.01% of dry weight. Another characteristic oftrue

alkaloidis that it always contains more than one

alkaloid.

y E.g. Ricinine is only alkaloid in Ricinus communis

and Genitianine only alkaloid in Gentianaceae, thatswhy these two bases have been kept outside the class

of true alkaloids.

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C. The type of alkaloids that can be

distinguished -

y It has been found that amino acidsphenylalanine,ornithine, tryptophan, lysine, histidine, Anthranilic acidare primary precursors of alkaloids in plants.

y Each of these amino acid can be regarded as starting pointfor synthesis of one or more types of alkaloids.

y Therefore we may put the alkaloids into familiescorresponding to six amino acids mentioned above.

y There are also numbers of alkaloids which can be regardedas hybrids.

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E.g.

y Phenylalanine family Hardenine, Ephedrine,Anahaline group, Papaverine group, Morphine group.

y Tryptophan family - Ajamaline, Yohimbine, vinblastine

etc.

y Ornithine family - Hygrine, Atropine, Ecgonine etc .

y

Lysine family - Coniine, Anabasine etc.

.

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D. Homologous and analogous chemical

characters

y Two similar substances or even same substance maybe isolated from two different plants and aretaxonomically important if the compounds are derived

from exactly same metabolically process.y But same compounds or similar compounds are

produced by different metabolic pathways in differentplants.

y E.g.

Anabasine in Nicotianagenus(Solanaceae family) isformed from one molecule oflysine on the other handin Leguminosae family two molecules of lysine areinvolved. Thus it seems that Anabasine of Solanaceae isnot equivalent (homologous) to that in Leguminosae.

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y Similarly quinine has been isolated from several

unrelated genera.

y The quinoline alkaloids ofcinchona bark are

obviously quite different structurally from yohimbine

alkaloids from yohimbe bark but they are closelyrelated biosynthetically and this points to a close

relation between the plants in which they occur.

y Generally ornithine and lysine families of alkaloidsare closely related. Therefore, they should be treated as

one unit from chemotaxonomic point of view.

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Some examples of alkaloid distribution

and significance in taxonomy-

y Alkaloids are not universally accumulated by plants; some familiesare rich in alkaloidal species, such as

Berberidaceae, Leguminosae, Solanaceae, Rutaceae,Rubiaceae, Compositae, Liliaceae and Orchidaceae

yPapaveraceae is rich in isoquinoline alkaloids

y Legumes are rich in lupin alkaloids

y Solanaceae is rich in tropane alkaloids

y Rubiaceae is rich in quinoline alkaloids

Some alkaloids are restricted to only very certain plants

e.g.

y Morphine is restricted to P. somniferum

y Coniine is restricted to umbeliferous sp.

y Strychnine is restricted to strychnos species

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y Accumulation ofIsoquinoline alkaloids in familiesfumariaceae andPapaveraceae, indicate that there is closerelationship between two families. Both families accumulateIsoquinoline alkaloids, and always contain Protopine.

y There are instances where alkaloid biosynthesis can behelpful to chemotaxomist for arranging the species within

genus according to their alkaloid content.

y In the case of genus argemone,which is difficult to classifypurely on the basis of morphological grounds, the speciescan be arranged into three groups on the basis of theiralkaloid content.

y Group I contains alkaloid ofProtopine and Berberine butnotpavine type.

y Group II contains all three types.

y Group III contains only pavine types.

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Evidences from basic moiety

Pyridine and Piperidine

The parent base pyridine occurs in some plants as

y Lobeline obtained from Lobelia inflata family Lobeliaceae.

y Nicotine obtained from Nicotiana tobaccum familysolanaceae .

y Anabasine obtained from Nicotiana gluaca familychenopodiaceae.

y Anabasine occurs in tobacco, where it is formed from lysine

and nicotinic acid. In the legume and chenopod specieswhereAnabasine also occurs, it can be synthesized fromtwo molecules of lysine.

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Isoquinoline Alkaloids

y Isoquinoline alkaloids are obtained from following

plants.

y E.g. Papaverine is obtained from P. somniferum

family Papaveraceae

y Berberine is obtained from Hydrastis canadensisfamily Berberidaceae

y The amino acid phenylalanine and tyrosine act as

precursor for isoquinoline nucleus.y Hydrastinewhich is found in Berberidaceae and

Rannunculaceae.

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Tropane alkaloids

y Among the best-known members of the group are the

solanaceae alkaloids, which are very characteristic of

the solanaceae. Atropine and Hyoscyamine serve as

example.

y In erythroxylum, cocaine alkaloids are found which

are same in nucleus but do not occur in the solanacae.

y Ornithine is the precursor

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Indole Alkaloids

Indole alkaloids are found in following plants.

y Physostigmine obtained from Physostigma venonsum familyLeguminosae.

y Yohimbine obtained from Rauwolfia serpentina familyApocyanaceae.

y Vinblastine obtained from Catharanthus roseusfamilyApocyanaeae.

y Indole alkaloids origination from Phenylalanine as in Erythriaalkaloids (Leguminosae) such as Erysopine.

y In most cases e.g. Tryptamine (Loganiaceae), yohimbine(Apocyanaceae) and strychnine (Loganiaceae) the parentcompound is tryptophan.

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References

Chemical Plant Chemotaxonomy By T. SwainAcademic Press Second Edition 1965 Page No. 41-100,389-451.

The chemotaxonomy of Plants, By P.M. Smith

Contemporary Biology (edition 1975) Page No. 90-105.

The Textbook of Industrial Pharmacognosy by A.N.Kalia, 1st edition 2005.

http://en.wikipedia.org/wiki/chemotaxonomy.

www/nature.com//v84/n4/fig tan/3700056f3.html

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THANK YOU