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. 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
CHEMICAL TEST FOR TRITERPENOIDS AND STEROIDS
(a) Libermann-Burchard test: The extract is boiled with acetic anhydride (few ml) and cooled. Then concentrated sulphuric acid is added from the side wall of test tube brown
ring forms at the junction of two liquids. The upper layer turns green and deep red colour develops.
(b) Salkowski test: When extract is treated with concentrated sulphuric acid (few drops),
a red colour develops in lower layer (due to the presence of steroids) or yellow colour develops (indicates the presence of triterpenoids).
(c) Sulfur powder test: In this test sulphur powder is added in test solution which sinks at the bottom of test tube indicates the presence of phytoconstituents.
CHEMICAL TEST FOR CARDIAC GLYCOSIDES
(a) Baljet reaction: When test solution is treated with picric acid (or sodium picrate) yields a stable orange colour. These reactions are negative with saponin and either
negative or much weaker with bufadenolides.
(b) Raymond test: When test solution is added in hot methanolic alkali solution, a violet colour develops.
(c) Legal test: When aqueous or alcoholic extract is treated with pyridine (1 ml) and sodium nitroprusside (1 ml) solution, pink to blood red colour appears.
(d) Killer-killani test: Take chloroform extract and dry it. Then add glacial acetic acid (0.4 ml) along with traces of ferric chloride. Transfer the content in small test tube and add concentrated sulphuric acid (0.5 ml) by the sidewall of the test tube. Acetic acid solution slowly turns bluish green in colour indicates the presence of deoxy sugars.
(e) Xanthydrol test: When extract is heated with Xanthydrol solution (5 percent) in glacial acetic acid and hydrochloric acid (1 percent), a red colour develops indicates the presence of 2-deoxysugar.
(f) Antimony trichloride test: Add antimony trichloride and trichloro acetic acid into a
solution of glycoside and heat the solution, blue or violet colour appears indicates
the presence of cardenolides and bufadenolides.
[I] LIQUORICE (click here)
[II] DIGITALIS (click here)
[III] DIGITALIS LANATA (click here)
[IV] DIOSCOREA (click here)