Alkaloids are basic nitrogenous compounds derived from plants and other organisms, first identified in 1819, with a wide range of pharmacological effects including analgesic, antimalarial, and psychotropic activities. They serve various functions in plants such as protecting against pests and assisting in growth, while also having significant uses in medicine and other applications for humans. However, they can exhibit toxicity at higher doses, affecting multiple organ systems and modulating neurotransmitter activity.

1. ALKALOIDS

2. CONTENTS
• Introduction
• History
• Classification
• Properties
• Functions
• Uses
• Effects of alkaloids on humans
• Extraction of alkaloids
• Biosynthesis of alkaloids
• Conclusions
• References

3. Introduction
• The name alkaloids was introduced in1819 by the German chemist
Friedrich Wilhelm Meibner, and is derived from Latin , root alkali which
inturn, comes from the Arabic- meaning ashes of plant
• The term alkaloids are used to designate basic nitrogenous compounds of
plant origin that are physiologically active
• Alkaloids are produced by a large variety of organisms including bacteria,
fungi, plants and animals
• The first individual alkaloid, morphine was isolated in 1804 from the
opium poppy
• Friedrich serturner, the German chemist to isolate morphine from opium
poppy

4. • Alkaloids have a wide range of pharmacological activities including
antimalarial (e.g: quinine)
• Antiasthma(e g: ephedrine)
• Cholinometric(e.g: galantamine)
• Vasodilatory(e.g: vincamine)
• Antiarrhythmic (e.g : quinidine)
• Analgesic (e.g: morphine)
• Antibacterial (e.g : Chelerythrine)
• Antihyperglycemic activities (e.g : piperine)
• Other alkaloids posses psychotropic ( e.g : psilocin) and other
stimulant activities (E.g : Cocaine, caffeine, nicotine, theobromine)
• Toxic alkaloids like adropine, tubocurarine

5. History
• Alkaloid containing plants have been used by humans since ancient
times for therapeutic and recreational purposes
• The Odyssey of Homer reffered to a gift given to Helen by the
Egyptian queen, a drug bringing oblivion
• It was believed that the gift was an opium containing drug
• A Chinese book on houseplants written in 1st – 3rd centuries BC
mentioned a medicinal use of ephidra and opium poppy
• The extract from plants containing toxic alkaloids, such as aconitine
and tubocurarine were used since antiquity for poisoning arrows

6. • The first complete synthesis of an alkaloid was achieved in 1886 by
the German chemist Albert Ladenburg
• NAMING:
Many individual names are formed by adding the suffix “ine” to the
species or genus name
E.g: Atropine is isolated from the plant Atropa belladona
Strychnine is obtained from the seed of the Strychnos nux-vomica
L.

7. Classification
1. Biosynthetic classification:
• . In this particular instance the significance solely, lies to the
precursor from which the alkaloids are produced in the plant
biosynthetic ally
• Example: indole alkaloids derived from tryptophan
• Piperidine alkaloids derived from lysine
• Pyrrolidine alkaloids derived from ornithine
• Phenylethylamine alkaloids derived from tyrosine
• Imidazole alkaloids derived from histidine

8. • Chemical classification:
• The main criterion is the presence of the basic heterocyclic
nucleus
• Examples:-
• Pyrrolidine alkaloids ( Hygrine )
• Piperidine alkoloids( Lobeline)
• Pyrrolizidine alkaloids ( Senecionine)
• Tropane alkaloids (Atropine)
• Quinoline alkaloids (quinine)

9. • Pharmacological classification:-
• This is used as a strong basis for the general classification of the
• Widespectrum of alkaloids derived from the plant kingdom such as
analgesics, cardiovascular drugs, CNS- stimulants and depressants,
dilation of eye pupil , mydriatics, anticholinergics,
sympathomimetics, antimalarial, purgatives
• Examples:-
• Morphine as narcotic analgesic
• Quinine as antimalarial
• Strychnine as reflex excitability
• Lobeline as respiratory stimulant
• Boldine as choleretics and laxatives

10. • Taxonomic classification:-
• This particular classification essentially deals with the 'taxon’ i.e.,
taxonomic category
• The most common taxa are the genus, subgenus, species,
subspecies and variety
• Cannabinaceous alkaloids:- e.g- Cannabis sativa (Hemp)
• Rubiaceous alkaloids:- e.g:- Cinchona (quinine)
• Solanaceous alkaloids:- eg:- Atropa belladona L. , Capsicum annum
L. ( Sweet potato,paprika)

11. • Non-heterogenous alkaloids

12. • Heterogeneous alkaloids

14. PROPERTIES OF ALKALOIDS
• PHYSICAL PROPERTIES
• 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 or non- volatile – e.g:- Pilocarpine and
hyoacine

15. • Colour:
• The majority of alkaloids are colourless but some are coloured
• E g: Colchicine and berberine are yellow
• Canadians is orange
• The salts of sanguinarine are copper-red
Solubility:
• Both alkaloidal bases and their salts are soluble in alcohol
• Generally the bases are soluble in organic solvents and insoluble in water

17. • Exceptions:
• Bases soluble in water : caffeine, ephedrine, Codeine, colchicine,
Pilocarpine and Quaternary ammonium bases
• Bases insoluble or sparingly soluble in certain organic solvents:
morphine in ether, theobromine and theophylline in benzene
• Salts insoluble in water: quinine monosulphate
• Salts soluble in organic solvents: Lobline and apoatropine,
hydrochloride are soluble in chloroform

18. • CHEMICAL PROPERTIES
• Most of the alkaloids are basic in nature, due to the availability of lone pair
electrons on the nitrogen
• The basic character of the alkaloid compound is enhanced if the adjacent
functional groups are electron releasing
• The alkaloids turn to be neutral or acidic when the adjacent functional
groups are electron withdrawing like amide group which reduces the
availability of lone pair of electrons
• Their salt formation with an inorganic acid prevents many a time their
decomposition
• In the natural form, the alkaloids exists either in free State as amine or as
salt with acid or alkaloid N- oxides

19. Functions of alkaloids in plants
• They may act as the reservoirs of protein synthesis
• They may act as protective substances against the insect or animal attacks
• Like hormones, they may function as plant stimulants or regulators in
activities like growth, metabolism and reproduction
• They may function as detoxicating agents by methylating, condensing and
cyclizing the compounds whose accumulation might cause damage to the
plant
• They may be utilised as the source of energy in case of deficiency in carbon
dioxide assimilation
• Source of nitrogen in case of nitrogen deficiency

20. Uses of alkaloids
• Alkaloids showed strong biological effects on animal and human organisms in very small
doses
• Alkaloids are present not only in human daily life in food and drinks but also as stimulant
drugs
• They showed anti-inflammatory, anticancer, analgesics, local anaesthetic and pain relief,
neuropharmacologic, antimicrobial, antifungal and many other activities
• Alkaloids are useful as diet ingredients, supplements and pharmaceuticals in medicine
and in other applications in human life
• Alkaloids are also important compounds in organic synthesis for searching new
semisynthetic and synthetic compounds with possibly better biological activity than
parent compounds

21. Effects of alkaloids on humans
• Alkaloids are produced by many plants as defense chemicals not only
mainly against herbivores but also against microbial pathogens
• Many alkaloids exhibit a pronounced toxicity in animal models and
humans
• A major target in animals is the nervous system and many alkaloids
structurally resemble neurotransmitters
• Because of structure similarity, they can interfere with
neurotransmitter receptors or ion channels and thus modulates
neuronal signal transduction

22. • Also other organs can be affected by toxic alkaloids such as the liver,
kidney, heart and circulation, gatrointestinal tract and reproductive
organs
• At a molecular level, alkaloids can interfere with membrane
permeability, membrane proteins (ion channels and receptors),
enzymes and other proteins, DNA, RNA and corresponding proteins,
electron chain and the cytoskeleton
• Because of these pharmacological properties, some alkaloids can be
used in medicine to treat infections, health disorders and even cancer

23. Extraction of alkaloids
• STAS- OTTO METHOD:
• The technique involve the distribution of alkaloidal bases between
acid or aqueous solution and immiscible organic solvents
• Stage 1 :- The powdered material is moistened with water and mixed
with alkali like sodium and potassium carbonate, ammonia, lime.
Make a paste with water, dry, repowder
• Stage 2 :- Extract the free alkaloids by hot continuous percolation
with chloroform or any other organic solvents

24. • Stage 3:- agitate the chloroform solution witb successive portion of
dilute sulphuric acid separating the aqueous layer before adding the
next portion of acid
• Stage 4 :- make the mixed aqueous liquid alkaline with ammonia,
collect the precipitate that forms, wash with water and dry

26. Biosynthesis of alkaloids
• Biological precursor of most alkaloids are amino acids such as,
ornithine, lysine, phenylalanine, tyrosine, tryptophan, histidine,
aspartic acid,etc.
• SYNTHESIS OF SCHIFF’S BASES
• Schiff’s bases can be obtained by reacting amines with ketones or
aldehydes
• These are common method of producing C=N bonds

27. • In the biosynthesis of alkaloids such reactions may take place within
a molecule. Such as in the synthesis of piperidine

28. Mannich reaction
• An integral component of the Mannich reaction in addition to an
amine and carbonyl compound is a carbanion which plays the role of
the nucleophile in the nucleophilic addition to the ions formed by the
reaction of amine and carbonyl

29. • The Mannich reaction can produce both intermolecularly and
intramolecularly

30. Dimer alkaloids
• In addition to the described monomeric alkaloids, there are dimeric
and even trimeric and tetrameric alkaloids formed upon condensation
of two, three and four monomeric alkaloids
• Dimeric alkaloids are usually formed from monomers of same type
• Mannich reaction resulting in e.g: Vocamine
• Condensation of aldehydes with amines resulting in toxiferine

32. Conclusions
• Alkaloids are basic nitrogenous compounds which are of great
medicinal properties
• It becomes toxic when given in high quantity
• And it acts as medicine when given in small quantity

33. References
• Andreas Luch(2009), Molecular, clinical, environmental toxicology,
Springer,p20
• R.H.F Manske(1965).,The alkaloid chemistry and physiology,vol VIII ,
Newyork, Academic press, p-673
• www.pharmacology.in/alkaloidsclassification

34. •Thank you...