Isolation, Identification and Analysis of Terpenoids:
• Brief study about Isolation, Identification and Analysis of Alkaloids:
• Brief study about method of Isolation, Identification and Analysis of Glycosides:
o Glycyrhetinic acid
• Brief study about method of Isolation, Identification and Analysis of Resins:
Isolation of Menthol
Occurrence: Menthol is a monoterpene alcohol found in mint oil or peppermint oil. The sources of mint oil are Mentha piperita Var. vulgaris, Mentha piperita Var. officinalis, Mentha arvensis, Mentha canadensis Var. piperascence belongs to the family Piperaceae. 1 to 3 percent volatile oil is present in peppermint. The two varieties Mentha piperita Var. vulgaris and Mentha piperita Var. officinalis contains not less than 45 percent of menthol whereas the varieties Mentha arvensis and Mentha canadensis Var. piperascence contains upto 70 to 90 percent of menthol. The other constituents are (+) neomenthol, (+) isomenthol, menthofuran, menthone, menthyl acetate and cineole. Menthol can be synthesized chemically by hydrogenation of thymol. Isolation: Mentha oil is obtained by hydro distillation and steam distillation of fresh parts of mentha plant. For the isolation of (-) menthol from peppermint oil the oil is subjected for cooling. The menthol crystal crystallizes out and separated by centrifugation. The corn mint oil is obtained from steam distillation of Mentha arvensis flowering tops which contains about 70 to 80 percent of free (-) menthol. The oil is cooled and menthol crystals are separated by centrifugation. Pure (-) menthol is obtained from recrystallisation from low boiling solvents. The Melting point of menthol is 41 to 44°C. Thin layer chromatography of Menthol: 1 mg menthol is dissolved in 1 ml of methanol. Then apply a spot on silica gel-G plate and elute it in chloroform. The dried plates are sprayed with 1 percent vanillin-sulphuric acid reagent. Heat the plate at 110°C for 10 minutes. The Rf value of menthol is 0.48 to 0.62.
1. 10 mg menthol crystals are dissolved in 4 drops of concentrated sulphuric acid and add few drops of vanillin sulphuric acid reagent. It shows orange yellow colour which changes to violet upon addition of few ml of water.
2. Crystals of menthol are dissolved in glacial acetic acid and add 3 drops of sulphuric acid and one drop of nitric acid. Menthol does not give green or blue green colour (thymol gives green colour).
Isolation of Citral Occurrence: Citral occurs abundantly in lemongrass oil Cymbopogan flexuosus (Nees) stapf and Cymbopogan citrates (DC) stapf belongs to the family Graminae. Lemongrass contains about 75 to 85 percent of citral in their oil. It also occurs in verbena oil, lemon, lime, orange and ginger root. Citral is also present in other species like Ocimum pilosum (contains 35 percent), Liptospermum citratum, Eucalyptus staigeriana and other citrus species.
Citral Isolation: The lemongrass oil is shaken with 5 percent sodium bisulphate solution for 25 to 30 minutes. The resultant is first separated on Buchner funnel and washed with solvent ether or ethanol. The crude citral is regenerated by decomposing the sodium bisulphate adducts with dilute sodium hydroxide solution. The pure citral is obtained by distillation of crude citral under reduced pressure. Its boiling point is 92 to 93°C. Separation of Geranial (Citral-a) and Neral (Citral-b): It was observed by Tiemann that geranial (Citral-a) is obtained free from neral (Citral-b) during the regeneration process from bisulphate adduct. The crystalline sodium bisulphate adduct of Geranial or Citral-a is sparingly soluble in water whereas Neral or Citral-b adduct is readily soluble in water. Tiemann observed that neral is isolated from citral (mixture) by
shaking it with alkaline cyanoacetic acid solution (NC.CH2.COOH) for short period of time when geranial reacts at much faster rate with acid than neral. Citral-a have melting point 108-
110°C and Citral-b melting point is 96°C.
Fig. 11.3: Chemical structure of geranial and neral
1. Citral is very sensitive to oxidizing agents (even exposure to air) and yields linalool which have intense yellow colour.
2. Geranial with Tollen’s reagent (ammoniacal silver nitrate) gives geranic acid
3. Geranial upon hydrogenation with sodium amalgum in acidic solution gives citronellal and citronellol.
1. What do you understand by terpenoids? Write in brief.
2. Write method of isolation and analysis of Menthol.
3. What are the identification tests for Menthol?
4. Write method of isolation and analysis of Citral.
5. What are the identification tests for Citral? Write in short.
6. Write method of isolation and analysis of Artemisin.
7. Write identification test for Artemisin.
8. What do you understand by alkaloids? Explain in short.
9. Write method of isolation and analysis of Atropine.
10. Write identification tests for Atropine.
11. Write method of isolation and analysis of Quinine.
12. What are the identification tests for Quinine?
13. Write method of isolation and analysis of Reserpine.
14. Write identification tests for Reserpine.
15. Write method of isolation and analysis of Caffeine.
16. Write identification test for Caffeine.
17. What are Thalleioquin and Murexide test? Describe in short.
18. What do you understand by glycosides? Explain.
19. Write method of isolation and analysis of Glycyrhhetinic acid.
20. Write identification tests for Glycyrhhetinic acid.
21. What are Liebermann and Liebermann Burchard test?
22. Write method of isolation and analysis of Rutin.
23. What are the identification tests for Rutin.
24. What is shinoda test? Describe in short.
25. What do you understand by resins? Explain.
26. Write method of isolation and analysis of Podophyllotoxin.
27. Write identification tests for Podophyllotoxin.
28. Write method of isolation and analysis of Curcumin.
29. Write identification test for Curcumin.
Isolation, Identification and Analysis of Phytoconstituents
a) Terpenoids: Menthol, Citral, Artemisin
b) Glycosides: Glycyrhetinic acid & Rutin
c) Alkaloids: Atropine,Quinine,Reserpine,Caffeine
d) Resins: Podophyllotoxin, Curcumin