Q.45 Which of the following plant-based secondary metabolites belong(s) to the class
of alkaloids?
(A) Ajmalicine (C21H24N2O3)
(B) Azadirachtin (C35H44O16)
(C) Camptothecin (C20H16N2O4)
(D) Vinblastine (C46H58N4O9)
Identifying Ajmalicine, Camptothecin, Vinblastine, and Azadirachtin in Secondary Metabolites
Alkaloids represent a key class of plant-based secondary metabolites defined by containing at least one nitrogen atom, often in a heterocyclic ring, derived from amino acids like tryptophan or tyrosine. These compounds play roles in plant defense and have medicinal value, such as in cancer treatment. In this multiple-choice query, options (A), (C), and (D) qualify as alkaloids due to their nitrogen-containing structures and biosynthetic origins.
Correct Answer
The plant-based secondary metabolites that belong to the class of alkaloids are (A) Ajmalicine (C₂₁H₂₄N₂O₃), (C) Camptothecin (C₂₀H₁₆N₂O₄), and (D) Vinblastine (C₄₆H₅₈N₄O₉). Option (B) Azadirachtin lacks nitrogen and belongs to limonoids.
Alkaloid Definition
Alkaloids are basic, nitrogenous compounds with potent physiological effects, typically synthesized via pathways involving decarboxylated amino acids. Their structures often feature fused rings with nitrogen, enabling bioactivity like cytotoxicity or antimicrobial action. Familiar examples include morphine and quinine, underscoring their pharmaceutical importance.
Option Breakdown
-
(A) Ajmalicine: This indole alkaloid from Rauvolfia species and Catharanthus roseus contains two nitrogen atoms in its yohimban skeleton, confirming its alkaloid status. It acts as an α-adrenergic antagonist with hypotensive properties.
-
(B) Azadirachtin: Extracted from neem (Azadirachta indica), this tetranortriterpenoid features an oxygen-rich formula (C₃₅H₄₄O₁₆) without nitrogen, classifying it as a limonoid rather than an alkaloid. It functions as an insect antifeedant.
-
(C) Camptothecin: An indole alkaloid from Camptotheca acuminata, its pentacyclic structure includes two nitrogens and inhibits topoisomerase I, making it a lead for anticancer drugs like topotecan.
-
(D) Vinblastine: A dimeric indole alkaloid from Catharanthus roseus with four nitrogens, it disrupts microtubules for chemotherapy use against lymphomas and Hodgkin’s disease.
Exam Relevance
For biology students or researchers in plant sciences, recognizing molecular formulas aids in classifying secondary metabolites quickly. Alkaloids like these often appear in exams on phytochemistry or pharmacology due to their clinical applications.
