Formation of persistent foams during plant extraction and concentration is a good indicator for the presence of saponins in the plant tissue.

1. Shake an aqueous alcoholic extract of the plant material in a test tube. Formation of persistent foam above the liquid surface indicates the presence of saponins. Stable foam in alkaline medium indicates the presence of steroid saponins. Pentacyclic triterpenoid saponins form foam that is stable both in alkaline and acidic media.
2. TLC test: To 10 g of the dried powdered plant material, add 100 ml of 1M hydrochloric acid and heat under reflux for 2 hours. Cool, neutralize with alkali, and evaporate to dryness. Extract with 3 × 30 ml chloroform and concentrate to about 15 ml. Spot it on a TLC plate and develop in acetone:hexane (4:1). Air dry and activate the plates by spraying with antimony trichloride in concentrated HCl. Sapogenins may be detected as pink or purple-coloured spots.
3. Liebermann–Burchard reaction: To a small quantity of the drug dissolved in alcohol, add a few drops of acetic anhydride followed by concentrated sulphuric acid. Formation of a bluish-green ring at the junction of two layers indicates the presence of steroids.
4. Sange’s test: To a solution of the saponin, add a solution of vanillin in sulphuric acid. [0.5 g in sulphuric acid-ethanol (4:1)]. Development of a yellow colour indicates the presence of steroidal saponins.
5. Lafon’s reaction: To a solution of the saponin in methanol, add a few drops of concentrated sulphuric acid and 1 ml of ferric sulphate solution. Formation of a bluish green colour indicates the presence of saponins.
6. To a solution of the saponin in water add 3 ml of 25% lead acetate solution. Formation of a dense precipitate indicates the presence of saponins.