Description
General introduction and brief description about Triterpenoids and steroids. • Pharmacognostic profile of following drugs: o Liquorice o Digitalis o Dioscorea 4.1 INTRODUCTION Triterpenoids are compounds with a carbon skeleton possessing 6-isoprene units which are biogenetically derived from squalene (acyclic C30 hydrocarbon). They are generally complex cyclic structures of alcohols, aldehydes or carboxylic acids. They generally have high melting point and optically active. Along with these they are colourless compounds which are crystalline in nature. These compounds are hard to characterize because of their less chemical reactivity. The Liebermann burchard reagent contains acetic anhydride with concentrated sulfuric acid produces bluish green colour with triterpenes and sterols. Triterpenoids comprises four groups of compounds: 1. True triterpenes 2. Steroids 3. Saponins 4. Cardiac glycosides HO HOHOa-Amyrin b-Amyrin g-SitosterolFig. 4.1: Chemical structures of α-Amyrin, β-Amyrin and γ-sitosterol Some triterpenes are well known and newer compounds are regularly being discovered and characterized. α-amyrin and β-amyrin and their derived acids, ursolic and oleanolic acids are some examples of pentacyclic triterpenes which exist in nature widely. These compounds
Chemical structure of Hecogenin, Yamogenin and Glycyrrhizin The last group of triperpenoids are cardiac glycosides or cardenolides. A typical cardiac glycoside is oleandrin (obtained from Nerium oleander, Apocynaceae). A considerable number of plants scattered throughout the plant kingdom contain C23 and C24 steroidal glycosides which exert on the failing heart a slowing and strengthening effect. Cardiac glycosides have a fairly limited distribution in several dozen genera unevenly scattered in about 15 families. The majority of the saccaharides found in the Cardiac glycosides are highly specific. They are 2, 6 di deoxy hexose such as D-digitoxose. In addition to these specific saccaharides 6- deoxy hexose also occurs. The cardiac activity is linked to the aglycone. The sugar moiety enhances the activity but does not participate directly in the activity and modulates it by modifying the polarity of the compound. The lactone at C-17, the presence of a X=C-C= function (where X is a hetero atom) is required and it must be in β- configuration. The activity is maximized when the A, B and C rings are in the cis, Trans, cis configuration. The activity is greatly diminished when the A and B ring are trans fused. The C and D ring must be cis fused. As a general rule the glycosides are fairly soluble in water and slightly soluble in C2H5OH and CHCl3, the lactone ring likely to open in an alkaline medium. The cardiac glycosides are mainly classified into two groups: 1. Cardenolides 2. Bufadienolides
QUESTIONS
1. What are Triterpenoids? Classify them with examples.
2. How triterpenes are extracted? Explain in flowchart.
3. What are the chemical tests for triterpenes and steroids?
4. Define cardiac glycosides. Classify them.
5. How cardiac glycosides are extracted?
6. What are the chemical tests for cardiac glycosides?
7. What are saponins? Write in short.
8. Write biological source, family and geographical source of liquorice.
9. Write a detailed pharmacognostic note on Glycyrrhiza.
10. Write method of cultivation and collection of liquorice.
11. Write biological source, family and geographical source of Digitalis.
12. Write method of cultivation and collection of Digitalis.
13. What is the main constituent of Digitalis? Draw it chemical structure.
14. Write about Killer killani test and other test of Digitalis.
15. Write about the allied drug of Digitalis.
16. Draw an interconversion flowchart of Digitalis constituents (lanatosides).
17. Write biological source, family and geographical source of Dioscorea.
18. What are the chemical constituents and uses of drug Dioscorea?
19. Write method of cultivation and collection Dioscorea.
20. Which are the allied drugs of Dioscorea?
