Coumarins and terpenoids: umbelliferone, cucurbitacins MCQs With Answer

Introduction: This quiz set focuses on coumarins and terpenoids—specifically umbelliferone (7-hydroxycoumarin) and the cucurbitacins—topics commonly encountered in the M.Pharm phytochemistry syllabus. Questions are designed to probe structural features, biosynthetic origins, chemical reactions, spectral properties, pharmacological activities, analytical techniques, and safety considerations. Emphasis is placed on connecting chemical structure to biological function and isolation/analysis methods used in pharmaceutical research. The level is appropriate for postgraduate pharmacy students preparing for exams or practical work in natural products chemistry and drug discovery.

Q1. What is the correct chemical name for umbelliferone?

• 6-hydroxycoumarin
• 7-hydroxycoumarin
• 4-hydroxycoumarin
• 3-hydroxycoumarin

Correct Answer: 7-hydroxycoumarin

Q2. Umbelliferone is biosynthetically derived from which primary pathway?

• Shikimate/phenylpropanoid pathway
• Methylerythritol phosphate (MEP) pathway
• Polyketide pathway
• Alkaloid biosynthetic pathway

Correct Answer: Shikimate/phenylpropanoid pathway

Q3. Which structural feature defines coumarins like umbelliferone?

• A fused benzene and γ-lactone (chromen-2-one) ring system
• A steroidal four-ring nucleus
• An isoprene polymer chain with multiple double bonds
• A benzofuranone core

Correct Answer: A fused benzene and γ-lactone (chromen-2-one) ring system

Q4. Umbelliferone exhibits a characteristic spectral property useful for detection. What is it?

• Strong blue fluorescence under UV light
• Red fluorescence under visible light
• Characteristic odor detectable by GC-MS
• Intense IR band at 2500 cm-1

Correct Answer: Strong blue fluorescence under UV light

Q5. The immediate biosynthetic precursor to coumarins such as umbelliferone is generally considered to be:

• o‑Hydroxycinnamic acid (o‑coumaric acid) followed by lactonization
• Geranyl pyrophosphate followed by cyclization
• Acetyl-CoA via polyketide condensation
• Squalene oxidation

Correct Answer: o‑Hydroxycinnamic acid (o‑coumaric acid) followed by lactonization

Q6. Which common qualitative test is most useful to detect coumarins in plant extracts?

• Fluorescence inspection under UV light after extraction with alcohol
• Keller-Kiliani test for glycosides
• Dragendorff’s reagent for alkaloids
• Lead acetate test for sulfides

Correct Answer: Fluorescence inspection under UV light after extraction with alcohol

Q7. The cucurbitacins are best classified chemically as which type of natural product?

• Triterpenoids with a cucurbitane skeleton
• Monoterpenes derived from geraniol
• Flavonoid glycosides
• Alkaloids derived from tryptophan

Correct Answer: Triterpenoids with a cucurbitane skeleton

Q8. Which biosynthetic pathway produces cucurbitacins?

• Mevalonate (MVA) pathway producing triterpenes
• Shikimate pathway producing aromatic amino acids
• Polyketide synthase pathway
• Methylerythritol phosphate (MEP) pathway exclusively

Correct Answer: Mevalonate (MVA) pathway producing triterpenes

Q9. Which cucurbitacin is commonly reported as highly biologically active and frequently studied for anticancer effects?

• Cucurbitacin B
• Cucurbitacin A
• Cucurbitacin K
• Cucurbitacin T

Correct Answer: Cucurbitacin B

Q10. One known cellular mechanism of cucurbitacin anticancer activity involves inhibition of which signaling component?

• STAT3 (Signal Transducer and Activator of Transcription 3)
• Cyclooxygenase-2 (COX-2) enzyme directly
• Topoisomerase II exclusively
• Reverse transcriptase

Correct Answer: STAT3 (Signal Transducer and Activator of Transcription 3)

Q11. A distinguishing chemical test for triterpenoids including cucurbitacins is:

• Liebermann–Burchard reaction (green/blue color with steroidal/triterpenoid frameworks)
• Millon’s test (specific for phenolics)
• Foam test (for saponins only)
• Biuret test (for proteins)

Correct Answer: Liebermann–Burchard reaction (green/blue color with steroidal/triterpenoid frameworks)

Q12. Which functional group is essential to the lactone ring of coumarins and defines their reactivity?

• α,β‑Unsaturated γ‑lactone (conjugated enone lactone)
• Primary alcohol group
• Tertiary amine group
• Carboxylic acid free group only

Correct Answer: α,β‑Unsaturated γ‑lactone (conjugated enone lactone)

Q13. In HPLC analysis of umbelliferone in herbal extracts, which detector mode is commonly used because of its sensitivity for coumarins?

• Fluorescence detector (FLD)
• Refractive index detector (RID)
• Evaporative light scattering detector (ELSD)
• Conductivity detector

Correct Answer: Fluorescence detector (FLD)

Q14. Structural modifications on the umbelliferone nucleus at the 6- or 8-positions typically affect which property most directly?

• UV absorption maxima and fluorescence intensity
• Molecular weight without affecting spectra
• Conversion to steroid scaffold
• Ability to form glycosides only

Correct Answer: UV absorption maxima and fluorescence intensity

Q15. Which safety consideration is most relevant when working with cucurbitacin-rich plant extracts in the lab?

• They may be highly cytotoxic and can cause severe gastrointestinal irritation if ingested
• They are completely non-toxic and safe to taste
• They are volatile and pose inhalation explosion risk
• They are strong oxidizing agents that corrode glassware

Correct Answer: They may be highly cytotoxic and can cause severe gastrointestinal irritation if ingested

Q16. Which botanical family is a classical source of umbelliferone and led to its name?

• Apiaceae (Umbelliferae)
• Fabaceae
• Solanaceae
• Poaceae

Correct Answer: Apiaceae (Umbelliferae)

Q17. Which analytical technique provides detailed structural information (including oxygenation pattern) for cucurbitacins isolated from plants?

• NMR spectroscopy combined with HR-MS
• Paper chromatography alone
• Taste testing for bitterness
• Simple colorimetric pH test

Correct Answer: NMR spectroscopy combined with HR-MS

Q18. Glycosylation of coumarins (formation of O‑glycosides) typically results in which pharmaceutical-relevant change?

• Increased water solubility and altered bioavailability
• Complete loss of UV absorption
• Transformation into a triterpenoid scaffold
• Conversion into a volatile essential oil

Correct Answer: Increased water solubility and altered bioavailability

Q19. Which structural feature differentiates cucurbitacin types (e.g., B vs. E)?

• Different patterns of hydroxylation, ketones and acetylation on the cucurbitane core
• Presence or absence of a benzene ring fused to the lactone
• Whether they contain sulfur atoms in the skeleton
• Chain length of an isoprenoid tail only

Correct Answer: Different patterns of hydroxylation, ketones and acetylation on the cucurbitane core

Q20. Which pharmacological property is commonly attributed to umbelliferone and its homologs?

• Photoprotective, antioxidant and anti-inflammatory activities
• Strong opioid receptor agonism
• Direct inhibition of DNA polymerase delta
• Proconvulsant activity at low doses

Correct Answer: Photoprotective, antioxidant and anti-inflammatory activities

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