Which one of the following is the basic chemical test to identify anthracene glycosides in Aloes?

Question

Question

This question was previously asked in

RRB Pharmacist Exam Paper 2019

Answer 1

Correct Answer: Modified Borntrager test

Rationale:

The Modified Borntrager test is the specific chemical test designed to identify anthracene glycosides in plant materials such as Aloes.
This test involves a hydrolysis step to break down the glycosides into their aglycone anthraquinones, making it more sensitive and reliable for detecting anthracene glycosides.
In this test, the plant extract is treated with a strong acid to hydrolyze the glycosides, followed by treatment with an alkaline solution which allows the anthraquinones to exhibit a distinct color change, typically red or pink, indicating their presence.
The Modified Borntrager test can thus specifically and effectively confirm the presence of anthracene glycosides in Aloe and other similar plants.

Explanation of Other Options:

Keller Killiani test

The Keller Killiani test is used for the detection of cardiac glycosides, not anthracene glycosides. It involves a chemical reaction that produces a blue color in the presence of cardiac glycosides.
Originating from the study of heart-related drugs like digitoxin and digoxin, this test is not suitable for identifying anthraquinones found in Aloe species.

Borntrager test

The Borntrager test also detects anthraquinones, but it is less sensitive than the Modified Borntrager test. It does not effectively identify anthracene glycosides directly from plant materials without the additional hydrolysis step used in the modified version.
The Borntrager test directly reacts with anthraquinones after treating the sample with a basic solution and can miss glycosidic bound forms present in certain plants.

Legal test

The Legal test is typically used to detect the presence of keto acids and ketonic substances. It involves a reaction with sodium nitroprusside and an alkali, which produces a deep red to purple color.
This test is relevant for compounds like acetone and does not relate to the detection of anthracene glycosides in Aloe.

Conclusion:

To specifically and reliably identify anthracene glycosides in Aloe, the Modified Borntrager test is the appropriate choice. The additional hydrolysis step in the modified version makes it more accurate in detecting these compounds.