Page 81 - Pharmd general phytochemistry I-Final2024_LEUCTERS

The different anthracene derivatives contained by the crude drug
are said to exert a synergistic action. So, the crude drug materials
and the crude extracts are preferred over the pure isolated active
principle.

Structure-Activity Relationship:

Chemical tests for identification:
Borntrager’s Reaction:
+ve results with anthraquinones (The free aglycones).
• The glycosides are extracted and hydrolyzed by boiling the drug

with mineral acids.
• The aglycones are extracted from the acidic solution with ether or

benzene.
• Upon shaking the ether or benzene layer with aqueous alkali or

ammonia solution, the aqueous layer assumes a deep-red colour,
because of the formation of anthraquinone salts.

Modified Borntrager’s reaction:
• Borntrager’s reaction can distinguish anthraquinones from

anthrones which do not give the test unless they are converted to
anthraquinone by oxidation with mild oxidants such as hydrogen
peroxide or ferric chloride.
• Dianthrones and aloins also respond negatively to
Borntrager’sreaction. However, if they are cleaved and then
oxidized to afford anthraquinones, then, they give a positive colour
reaction.

79