Occurrence and classification and function of alkaloids

Alkaloids introduction, Alkaloids classification, Alkaloids function, pharmaceutical applications of alkaloids, Examples of alkaloids, Some review questions related to alkaloids.

1. Occurrence and classification and function of alkaloids Presented by: Jasmine Juliet Biochemistry, Agricultural college &Research Institute, Madurai .

2. Alkaloid - Introduction Alkaloids are a group of molecules with a relatively large occurrence in nature around the globe. They are very diverse chemicals and biomolecules , but they are all secondary compounds and are derived from amino acids or from the transamination process . The most common precursor of alkaloids are aminoacids .

3. Alkaloids Alkaloids are nitrogen containing compounds having at leave some basicity . They are usually heterocyclic and occur primarily in higher plants and some microorganisms. They usually exhibit significant physicological activity in humans and animals and represent one of the largest and most diverse groups of secondary products. Poisons – conine Narcotics – morphine Stimulants – caffeine Medicine – Taxol

4. Alkaloids - Classification Alkaloids are broadly classified into True alkaloids – possess heterocyclic ring and are derived from amino acids. Eg . Nicotine, Quinine. Protoalkaloids – Do not possess heterocyclic ring but are derived from amino acids. Eg . Colchicine . Pseudoalkaloids – Not derived from amino acids. Eg . Caffeine, theophylline .

5. Alkaloids - Classification There are many other classification systems, which are based on taxonomy, pharmacological properties and their chemical nature . The chemical classification of alkaloids universally adopted depends on the heterocyclic ring structure present and is represented below.

6. Sl.no . Class Heterocyclic Example 1. Pyrrolidine Stachydirn 2. Pyridine Nicotine 3. Piperidine Conine 4. Tropane Atropine 5. Indole Reserpine

7. 6. Quinoline Quinine 7. Isoquinoline Emetine 8. Quinolizidine Lupinine 9. Pyrrolizidine Hellotridine 10. Quinazoline Peganine Sl.no . Class Heterocyclic Example

8. Alkaloids - Function Alkaloids play a defense role in plants against insects other arthropods and vertebrates. Some alkaloids function as antimicrobial compounds. Some alkloids have allelopathic effects. Many alkaloids possess physicoloigcal actions in humans. For example vinblastine and vincristine are potent anticancer drugs. Alkaloids act as reserve substances able to supply nitrogen. They are end products of detoxification meachanisms .

9. Alkaloids - Pharmaceutiacal uses of alkaloids Many alkaloids exhibit marked pharmacological activity, and some fine important uses in medicine. Atropine , present in Datura species is used widely in medicine as anticholinergic drug . It is also used to dilate the pupil eye surgery. Morphine and codeine are narcotic analgesics , and codeine is also an antitussive agent , less toxic and less habit-forming than morphine. Colchicines , from the corms and seeds of the autumn crocus, is used as a gout suppressant .

10. Alkaloids - Func tion Caffenine , which occurs in coffee, tea, and cocoa is a central nervous system stimulant ; it is used as an antidote to barbiturate and morphine poisoning . Emetine , the key alkaloid is used in the treatment of amebic dysentery and other protozoal infections . Ephedrine and related alkaloids occur in the genus Ephedra . Ephedrine acts at the nerve-nerve spaces. Since it causes peripheral contraction of arterioles it is used to correct low blood pressure conditions and also to dilate the pupil of the eye. As a broncho -dilator it is used in allergic conditions like asthma .

11. Alkaloids - Func tion The leaves of coca contain cocaine. Cocaine is the oldest local anesthetic known. Because of its systemic effect and the danger of addiction, its use is now restricted to ophthalimic surgery and surgery of the ear, nose and throat. Quninne , cinchonine , quindine and a number of other alkaloids are present in the barks of cinchona. Cinchona alkaloids have been used for the treatment of malaria for many years.

12. Alkaloids - Func tion Reserpine extracted from the roots and rhizomes of the genus Rauvolfia has been used as a sedative and hypnotic and for reducing blood pressure . The drug is now largely used in insanity and high blood pressure. It is more suitable for cases of mild anxiety or patients of chronic mental illness. Vinblastine and vincristine are alkaloids found in Catharanthusroseus . Vinblastine is mainly useful for treating Hodgkin’s disease , advanced testicular cancer and advanced breast cancer. Vincristine is mainly used to treat acute leukemia and other lymphomas . Digitoxin and digoxin are cardiac glycodiesobtrained from digitals. These alkaloids are used to treat congestive heart failure .

13. Review questions Choose the correct answer 1. Monomeric unit of terpenes a ) Isoprene b) amino acid c) Benzene 2. Which one of the following is an alkaloid? a) Geraniol b) Caffeic acid c) Azadirachtin d) Quinine 3. Shikimic acid pathway is involved in the synthesis of a) Phenolics b) Terpenes c ) Alkaloids d) Steroids 4. β-Carotene is a Monoterpene b) Diterpene c) Triterpene d) Tetraterpene 5. Azadirachtin is used for the control of a) Bacterial disease b) Insect c) Fungal disease d) Rodents

14. Review questions 6 . Compounds containing aromatic ring with one or more hydroxyl groups a) Terpenes b) Alkaloids c) Phenolics 7. Juglone is an example of compounds producing ------ effect that affects the growth of another species of plant. a) Amphipathic b) Amphoteric c) allelopathic 8. Sesquiterpenes contain ----- carbon atoms a) 5 b) 10 c) 15 d) 20 9. The diterpene plant hormone is a) Auxin b ) Giberellins c) Cytokinins d) Ethylene 10. The sesquiterpene plant hormone a) Auxin b) Giberellins c) Cytokinins d) Abscisic acid

15. Review questions Write short notes on 1. Secondary metabolites and their functions 2. Terpenes 3. Phenolics 4. Alkaloids  

16. Review questions Write in detail 1.What are phenolics ? Explain their occurance , classification and functions. 2.What are terpenes ? Explain their occurance , classification and functions. 3.Define alkaloids? Explain their occurrence, classification and pharmacological applications  

17. Thank you