Transcript PHG 322 lecture 1

‫بسم هللا الرحمن الرحيم‬
PHG 322
PHARMACOGONSY II
LECTURE 1
PRESENTED BY
ASSISTANT PROF. DR. EBTESAM ALSHEDDI
Office: second flour # 84
Email: [email protected]
Site:
faculty.ksu.edu.sa/10252
Topics to be covered: (cont.)
1) Plants containing Alkaloids (botanical and chemical

Introduction

Phenylalkylamine, Tropolone and Imidazole alkaloids

Pyridine and piperidine alkaloids

Tropane alkaloids

Quinoline and isoquinoline alkaloids

Opium alkaloids

Indole alkaloids

Carboline, purine, steroidal and terpenoidal alkaloids
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characters):
Topics to be covered:

Biomedical potential of marine natural products

Microalgae as a drug source

Biologically active substances from marine sponges
4
2) Marine derived drugs:
Topics to be covered:
3) Plants containing Glycosides (botanical and chemical
characters):

Introduction

Phenolic, cyanogenic and thioglycosides

Coumarins, flavonoidal glycosides and related

Anthracene derivatives

Cardiac glycosides

Saponins
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compounds
Topics to be covered:
4) Toxicological Pharmacognosy:

Poisonous plants

Plants as drugs of abuse

Hepatotoxic plants

Toxic mushrooms
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3) Herb-drug interactions
Important Book/Thesis: 
1
2
3
Book/Thesis
Editor or
Author
Pharmacognosy
Trease
16th edition
and Evans
‫النباتات السامة في‬
‫عبد هللا بن أحمد‬
‫المملكة العربية السعودية‬
‫األمير‬
Bioactive Marine
Bhakuni
Natural Products and Rawat
Date of
pub.
2009
Name of Publisher
Saunders
London, New York, …
‫جامعة الملك سعود‬
2000
‫كلية العلوم‬
‫قسم النبات واألحياء الدقيقة‬
2005
Anamaya Publishers,
New Delhi, India
7
No.
The assessment tasks during the semester: 
Marks
Assessment task
Dr. Ebtesam
Dr. Rababb
First ½ of semester
(Exam + Activity/Quiz)
18
-
Second ½ of semester
-
18
Final Exam
Total
24
20
20
100
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Practical
Alkaloids
Definition
Alkaloids, which mean alkali-like substances, are basic
nitrogenous compounds of plant or animal origin and generally
possessing a marked physiological action on man or animals.
• The nitrogen is usually contained in a heterocyclic ring system.
Deviation from Definition
1)
Some alkaloids are not basic e.g. Colchicine, Piperine,
2)
Few alkaloids contain nitrogen in a non-ring system
e.g. Ephedrine, Colchicine. Mescaline
3) Plant origin:
Some alkaloids are derived from bacteria, fungi, insects, frogs, animals.
Function of alkaloids in plants
1) Protective function against insects or herbivores
2) They are end products (detoxification)
3) Source for energy and reserve of nitrogen
DISTRIBUTION IN PLANT:
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
Nomenclature
 Alkaloids terminate with the suffix: (ine)

Genus name e.g. Atropine from Atropa

Species name e.g. Cocaine from Coca

Common name e.g. Ergotamine from Ergot

Physiological activity e.g. Emetine (emetic)

Discoverer e.g. Pelletierine from Pelletier
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 Their names may be derived from:
Prefixes and suffixes
These are, usually, added to the name of the parent
alkaloid and are used to designate related alkaloids,
generally present in the same plant.
Examples are:
I. Prefixes
1) Nor-: designates N-demethylation or N-demethoxylation
e.g. Nornicotine
2) Apo-: designates dehydration e.g. Apomorphine
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3) Iso-, Pseudo-, Neo- and Epi- indicate different types of isomers
II. Suffixes
1) –dine: designates isomerism as in case of the Cinchona alkaloids
quinine (l) & quinidine (d)
cinchonidine (l) & cinchonine (d)
2) –ine: indicates, in case of ergot alkaloids, a lower pharmacological
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activity e.g. ergotaminine is less potent than ergotamine
Physical properties:
1) Condition:
 Most alkaloids are crystalline solids
 Some are liquids
non-volatile
volatile
e.g. pilocarpine and hyoscine
e.g. nicotine and coniine
2) Colour:
 Most alkaloids
Some are coloured:
- colchicine & berberine
- canadine
orange
yellow
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
colourless
3) Solubility:
 Solubility of alkaloids & their salts is important because:
a) They are often administered in solution
b) Differences in solubility between alkaloids & their
salts is used for:
- isolation of alkaloids
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- purification from non-alkaloidal substances
Solvent
Alkaloidal bases
Alkaloidal salts
Alcohol
Soluble
Soluble
Soluble
except:
- morphine & psychotrine
→ insol. in ether
- theobromine &
theophylline
→ benzene (insol.)
H2O
Insoluble
except:
- caffeine
- ephedrine
- codeine
- colchicine
- pilocarpine
- quat. ammonium bases
Insoluble
except:
- lobeline hydrochloride
→ CHCl3 (soluble)
Soluble
except:
quinine sulphate
→ insoluble in H2O
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Organic
solvents
4) Optical activity:
 Many alkaloids are optically active due to ?
→ presence of one or more asymmetric carbon atom(s)
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• Optically active isomers may show different
physiological activities.
• l-ephedrine is 3.5 times more active than d-ephedrine.
• l-ergotamine is 3-4 times more active than dergotamine.
• d- Tubocurarine is more active than the corresponding
l- form.
• Quinine (l-form) is antimalarial and its d- isomer
quinidine is antiarrythmic.
• The racemic (optically inactive) dl-atropine is
physiologically active.
Chemical properties:
 Alkaloids contain: C, H, N
 Most of them contain oxygen
 Few alkaloids are oxygen free
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nicotine
coniine
CHEMICAL PROPERTIES:
I- Nitrogen:
Primary amines
R-NH2
e.g. Norephedrine
Secondary amines
R2-NH
e.g. Ephedrine
Tertiary amines
R3-N
e.g. Atropine
Quaternary ammonium salts R4-N e.g
d-Tubocurarine
II- Basicity:
R2-NH
>
R-NH2
>
R3-N
Saturated hexacyclic amines is more basic than
aromatic amines.
1) Nitrogen in alkaloids
Number of
nitrogen atoms
Type of amino
group
Basicity
1) Number of nitrogen atoms:
•
Usually one N atom
•
Some contain more than one → up to 5 N atoms
e.g. nicotine → two
ergotamine → five
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2) Type of amino group:
N in alkaloids → in form of amine
•
Primary
amino group
H
Secondary
amino group
R
R1
..
..
N
H
R2
N
Tertiary
amino group
Quaternary
ammonium ion
R1
R1
H
R2
..N
R3
R2
N
+
R4
R3
e.g.
Norpseudoephedrine
Ephedrine
Nicotine
Tubocurarine
3) Basicity:
 A lone pair of electrons on N atom → basic character
→ alkaloids resemble NH3 in chemical characters
→ form salts with acids without liberation of H2O
N:
Alkaloid
+ H+Cl-
[ ]
N
H
+
Cl -
Alkaloid hydrochloride
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Factors influencing the degree of basicity:
Structure of the molecule
e.g. degree of unsaturation
of heterocyclic ring
N
..
N
..
Pyridine
Piperidine
Piperidine alkaloids →
more basic than pyridine alkaloids
unsaturation decreases basicity
Presence & position of
other substituents &
fuctional groups
Electron
withdrawing gps
e.g.
carbonyl
group
decrease
basicity
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Electron
releasing
groups
e.g.
alkyl group
increase
basicity
→ Alkaloids may be:
 Neutral (not basic)
→ electron availability on
nitrogen atom decreases
→ due to the presence of acidic group(s)
e.g. alkaloids containing
carboxylic group
Narceine
e.g. phenolic alkaloids
Morphine
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 Amphoteric
Ricinine