Step 1: Understanding the Concept:
Chemical identification tests are used to detect classes of secondary metabolites. Anthraquinones are a common class of purgative glycosides found in plants like Senna, Aloe, and Rhubarb.
Step 2: Detailed Explanation:
1. Borntrager’s Test: This test is specific for free anthraquinones. The drug is boiled with dilute HCl (to hydrolyze glycosides) and then extracted with an organic solvent like chloroform. When ammonia is added to the solvent, the ammoniacal layer turns pink or red, indicating a positive result.
2. Modified Borntrager’s Test: This is used for C-glycosides (like in Aloe), involving ferric chloride.
3. Others: Keller–Killiani is for cardiac glycosides (Digitalis). Shinoda test is for flavonoids. Foam test is for saponins.
Step 3: Final Answer:
Senna contains sennosides (anthraquinone glycosides), which are identified using the standard Borntrager’s test.