Alkaloids

general introduction about alkaloid .it contain definition, classification etc.

1. Alkaloids

2. Prepared by Dr . N.GOPINATHAN ASSISTANT PROFESSOR DEPARTMENT OF PHARMACEUTICAL CHEMISTRY FACULTY OF PHARMACY SRIHER [DU] CHENNAI-116 TAMILNADU

3. Introduction Alkaloid the term is coined by pharmacist W. Meissner in 1819 for the basic, nitrogen containing compounds of plant origin. The basicity is due to presence of nitrogen inside the ring. It is physiologically active basic compounds of plant origin, in which at least one nitrogen atom forms part of a cyclic system.

4. The above definition is not fully satisfactory because some compounds although alkaloid do not confine to this definition. Adrenalin and ephedrine have nitrogen atom in the side chain. Ephedrine

5. Other compounds although not alkaloids confined to this definition . Only 10-15 % found in all vascular region. It is rarely found in lower plants like algae, fungi [ ergot alkaloid ].

6. Vascular tissue

7. History

8. Heterocyclic physiologically active nitrogen but not regarded as alkaloids Thiamine Purine caffeine theobromine xanthine

9. It exist as salt of plant acid such as acetic acid, oxalic acid, citric acid, malic , lactic , tartaric , tannic and aconiticacid .

10. Tartaric acid Aconitic acid

11. Cinchona alkaloid with quininic acid , and opium alkaoid with meconic acid.

12. Basicity of alkaloids

13. Distribution of alkaloid in plant

14. Other sources

15. Occurence

16. Occur in free form narceine and nicotine.

17. As glycoside – Solanum and veratrum .

18. As amides – Piperine

19. Esters- Tropine and cocaine.

20. Colchinine is regarded as alkaloid although it is not heterocyclic.

21. Thiamine is heterocyclic nitrogenous base because it is universally distributed in living matter so not included in alkaloid.

22. It is found in dicotyledons like Apocynaceae , Papaveraceae , Papilionaceae , Ranunculaceae , Rubiaceae , Rutacea , Solanaceae .

23. The purpose of existence of alkaloid in plant It is regarded as bye product of plant metabolism. It act as reservoir of protein synthesis . It act as protective substance against the animal or insect attack . It function as plant stimulant like growth, metabolism and reproduction. As detoxifying agent by methylation, condensing and cyclize the compounds.

24. Nomenclature Due to complex structure and some historical reason there was no systematic nomenclature of alkaloids. It is named according to the plants from which they are obtained. Papaverine – papaver somniferum . Berberine – berberis vulgaris.L

25. Few named after their physiological action such as M orphine [ G erman morphin - God of dreams ] Narcotine [ Greek narkov – be numb] Emetine [ G reek emetikos – to vomit ]

26. Some of it has been named after their discoveries pelletierine group P.J.Pelletier

27. Minor alkaloids named has been derived by adding one prefix or suffix to the name of principal alkaloid Cinchona series

28. Nomenclature Related bases have been named by transposition as narcotine , cotarine and tarconine . Prefix such as epi, iso,neo,pseudo etc.. Greek letters have been used to designate isomeric or slightly modified structure. The prefix nor denotes the structure which does not have a methyl group attached to the nitrogen atom.

29. Classification

30. Taxonomic It is done according to family. Alkaloids are described as solanaceous or papilionaceous without reference to chemical type. Both the families contain alkaloid of several type. Solanaxeae - tropane,pyridine steroidal Papilionaceae-Quinolizidine & pyrrolizidine. Disadvantage of the system is obvious.

31. Pharmacological classification It is based on their use or physiological activity. Analgesic, cardio active alkaloids. Alkaloids within a group frequently have chemical similarities.

32. Biosynthetic classification It is more fundamental method than chemical classification. It depends on the type of precursor or building block of compounds used by plants to synthesis complex structure. Hundreds of indole alkaoids are derived from the amino acid tryptophan and mevalonic acid as ergot or cinchona alkaloid.

33. Similarly morphine, papaverine , narcotine tubocurarine and colchinine may be listed as phenyl alanine tyrosine derived base. The disadvantage of this method is precursor which is not always apparent.

34. Chemical classification

35. 1. Phenylethylamine alkaloidEphedrine , adrenaline and nor adrenaline

36. 2.Pyrolidine alkaloid Hygrine , cusohygrine

37. 3.Pyridine Alkaloid- Ricinine , conine

38. 4.Piperidine Alkaloid piperine pelletierine

39. 5.Pyridine – pyrrolidine Alkaloid Nicotine

40. 6.Tropane alkaloid Atropine Cocaine

41. 7.Quinoline alkaloid Quinine, cinchonine

42. 8.Isoquinoline Alkaloid papaverine narcotine emetine

43. 9.Phenanthrene Alkaloid morphine

44. 10.Indole Alkaloid ergotamine, Reserpine Strychnine Brucine

45. 11.Tropolone alkaloid Colchioine

46. 12. Imidazole alkaloid

47. Isolation Isolation and purification of an alkaloid from a plant is always not a simple process. Plants may contain complex several alkaloids. Their isolation of an pure alkaloid may become an extremely laborious procedure. First of all the presence of an alkaloids in a plant is ascertained by employing various reagent called alkaloidal reagent

48. Chloroplatinic acid H 2 PtCl 6 , chloroauric acid HAuCl4, Phosphotringstic and molybdic acid are useful precipitating agent. The precipitate have characteristic colours and are used for the detection of alkaloids in very small amount. After detection seperation of alkaloids from plant. Final step is purification. For isolation of small quantity of an alkaloid chromatography is most satisfactory.

49. Other colouring reagents usedto detect alkaloids are Formaldehyde [ Marquis reagent] Nitric acid [ E rdmann’s reagent ] Molybdic acid [ Frende’s reagent ]

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