Alkaloids

Detailed study of alkaloids including its Definition, properties, types, classification, isolation/extraction

1. ALKALOIDS: Definition , classification, properties and test for identification

2. DEFINITION It is originate from alkali like word because of resemblance with the characters of naturally occurring complex amines. 2 . Alkaloids are basic in nature. 3 . These are organic products of natural or synthetic origin which contain one or more nitrogen atom usually in heterocyclic ring and it has marked physiological effect on human or other animal when used in small quantities.

3. Usually alkaloids are derivatives from amino acids. Even though many alkaloids are poisonous (e.g. strychnine or coniine), some are used in medicine as analgesics (pain relievers) or anaesthetics , particularly morphine and codeine. Most alkaloids have a very bitter taste.

4. Functions in plants Act as protective against insects and herbivores due to their bitterness and toxicity. Source of nitrogen in nitrogen deficiency Sometimes act as growth regulator

5. Types of alkaloids: There are three main types of alkaloids: (1) true alkaloids/ typical/ heterocyclic alkaloids (2) protoalkaloids / non-heterocyclic/ atypical alkaloids (3) pseudoalkaloids .

6. 1. True alkaloids: These are present in plants as salts of organic acids. They are basic in nature Toxic in nature Derived from amino acids Presence of nitrogen in the heterocyclic ring Example: Morphine and Quinine

7. 2 . Protoalkaloids : Nitrogen is not present in the heterocyclic ring but present in the side chain These are simple amines and basic in nature. Example : Ephedrine

8. 3 . Pseudoalkaloids : These are steroidal, terpenoidal and purines alkaloids. Not derived from amino acids They do not show typical characters of alkaloids but give standard test for alkaloids. Example : Caffeine ( Murexide test)

9. PROPERTIES 1.Physical properties: Colourless Crystalline solid It has sharp melting point Some are Amorphous gums example: Opium. Some are volatile and liquid Example is Nicotine Some are colored Example: Betadine is red in colour , berberrine is yellow in colour .

10. PROPERTIES 2 . Chemical properties: Most of the alkaloids are basic in nature due to the availability of non-pair of electron on nitrogen. Alkaloids become neutral/ acidic when adjacent functional groups are electron withdrawing. Example: Amide group.

11. Decomposition of alkaloids: Alkaloids show basic character and due to this they are very much sensitive to decomposition and cause a problem during storage because of this reason they are made into salt form. Alkaloids are insoluble in water Pseudo and proto alkaloids show more solubility in water. Example: Caffiene (freely soluble in water)

12. CLASSIFICATION OF ALKALOIDS:

13. CHEMICAL TESTS:

14. EXTRACTION/ ISOLATION: The extraction of alkaloids is based on their basic character and solubility profiles. Generally alkaloids are extracted mainly using two methods.