Q.6 Vincristine and vinblastine, two commercially important secondary metabolites from Carrants roses, are examples of
(A) alkaloids.
(B) flavonoids.
(C) terpenoids.
(D) steroids
Vincristine and vinblastine from Catharanthus roseus are vinca alkaloids, making option (A) the correct answer. These compounds are secondary metabolites extracted from the Madagascar periwinkle plant, commonly misnamed as “Carrants roses” in the question, which refers to Catharanthus roseus. They function as chemotherapy agents by binding to tubulin and disrupting microtubule formation during mitosis.
Option Analysis
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(A) Alkaloids: Correct. Vincristine and vinblastine belong to the vinca alkaloid class, which are indole alkaloids derived from Catharanthus roseus. They inhibit cell division by preventing microtubule assembly.
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(B) Flavonoids: Incorrect. Flavonoids are polyphenolic compounds with antioxidant properties, found in many plants but not classifying vincristine or vinblastine, which are nitrogen-containing alkaloids.
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(C) Terpenoids: Incorrect. Terpenoids (isoprenoids) include compounds like carotenoids and essential oils, but vinca alkaloids have a distinct dimeric structure with indole and dihydroindole units.
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(D) Steroids: Incorrect. Steroids feature a four-ring structure and function as hormones, unlike the alkaloid backbone of vincristine and vinblastine.
Vincristine and vinblastine alkaloids represent key secondary metabolites from Catharanthus roseus, also known as Madagascar periwinkle or Vinca rosea. These vincristine and vinblastine alkaloids are commercially vital in chemotherapy, targeting cancers like leukemia, lymphoma, and neuroblastoma by arresting cells in the M-phase of mitosis. Often featured in competitive exams like IIT JAM, questions test their classification as alkaloids over other plant metabolites.
Chemical Classification and Structure
Vincristine and vinblastine alkaloids form a subclass of vinca alkaloids, comprising monoterpenoid indole structures from catharanthine and vindoline precursors unique to Catharanthus roseus. Unlike flavonoids (pigments with antioxidant roles), terpenoids (volatile oils), or steroids (lipid hormones), these contain nitrogen in a basic heterocyclic ring, defining true alkaloids. Extraction involves leaf processing and chromatography for pharmaceutical purity.
Therapeutic Mechanism
These alkaloids bind tubulin, inhibiting microtubule polymerization essential for the mitotic spindle, leading to metaphase arrest and apoptosis in rapidly dividing cancer cells. Vincristine targets solid tumors and leukemias, while vinblastine suits Hodgkin’s lymphoma; both are M-phase specific, sparing non-dividing cells.
Exam Relevance for IIT JAM
In biology and biotech sections, vincristine and vinblastine alkaloids exemplify plant-derived drugs. Differentiate: alkaloids (nitrogenous bases like these), flavonoids (e.g., quercetin), terpenoids (e.g., taxol), steroids (e.g., diosgenin). Catharanthus roseus yields over 100 alkaloids, but these two drive 90% of its anticancer value.
