Alkaloid Case Studies: Ephedrine, Morphine, Ergot, Emetine, Reserpine MCQs With Answer

Alkaloid Case Studies: Ephedrine, Morphine, Ergot, Emetine, Reserpine MCQs With Answer

This quiz collection is designed for M.Pharm students studying MPC 104T (Chemistry of Natural Products). It focuses on in-depth case studies of key alkaloids—ephedrine, morphine, ergot alkaloids, emetine, and reserpine—covering structural features, biosynthesis, pharmacological mechanisms, analytical identification, toxicology and pharmaceutical aspects. Each question targets advanced comprehension and application relevant to drug development, analysis, and therapeutics. Use these MCQs to sharpen problem-solving, prepare for exams, and reinforce practical understanding of alkaloid chemistry and their clinical implications.

Q1. Which statement correctly describes the stereochemistry of ephedrine?

• Ephedrine has one stereogenic center and exists as two enantiomers
• Ephedrine has two stereogenic centers and exists as four stereoisomers
• Ephedrine is achiral due to an internal plane of symmetry
• Ephedrine has three stereogenic centers and exists as eight stereoisomers

Correct Answer: Ephedrine has two stereogenic centers and exists as four stereoisomers

Q2. In the biosynthetic pathway of morphine in Papaver somniferum, which intermediate is commonly regarded as the immediate precursor to morphine?

• Reticuline
• Thebaine
• Strychnine
• Noscapine

Correct Answer: Thebaine

Q3. Ergotamine’s pharmacological activity primarily involves interaction with which types of receptors to produce vasoconstriction?

• Muscarinic acetylcholine receptors only
• Beta-2 adrenergic receptors only
• Partial agonist activity at 5-HT1B/1D and alpha-adrenergic receptors
• NMDA and GABA receptors

Correct Answer: Partial agonist activity at 5-HT1B/1D and alpha-adrenergic receptors

Q4. Emetine, derived from ipecac, was historically used in the treatment of which condition?

• Hypertension
• Amoebic dysentery (amoebiasis)
• Migraine prophylaxis
• Parkinson’s disease

Correct Answer: Amoebic dysentery (amoebiasis)

Q5. What is the primary biochemical mechanism of action of reserpine that explains its antihypertensive effect?

• Inhibition of monoamine oxidase (MAO)
• Blockade of post-synaptic beta-adrenergic receptors
• Irreversible inhibition of the vesicular monoamine transporter (VMAT), depleting monoamines
• Competitive inhibition of catecholamine synthesis enzymes

Correct Answer: Irreversible inhibition of the vesicular monoamine transporter (VMAT), depleting monoamines

Q6. Which structural feature of morphine is most critical for high affinity binding to the μ-opioid receptor?

• The 3-phenolic hydroxyl group
• The 7,8-double bond in the morphinan core
• The 14-hydroxyl substitution
• The ether bridge between C4 and C5

Correct Answer: The 3-phenolic hydroxyl group

Q7. Ephedrine’s sympathomimetic action is best described as:

• Pure direct agonist at beta-2 adrenergic receptors only
• Direct antagonist at alpha-adrenergic receptors
• Mixed-acting: direct agonist at alpha and beta receptors and indirect by releasing norepinephrine
• Selective serotonin reuptake inhibitor

Correct Answer: Mixed-acting: direct agonist at alpha and beta receptors and indirect by releasing norepinephrine

Q8. Ergot alkaloids share a common tetracyclic core known as:

• Strychnine skeleton
• Ergoline ring system
• Isoquinoline nucleus
• Indolizidine framework

Correct Answer: Ergoline ring system

Q9. The most clinically significant toxic effect associated with emetine overdose is:

• Renal failure
• Severe cardiotoxicity leading to arrhythmias and heart failure
• Pulmonary fibrosis
• Thrombocytopenia

Correct Answer: Severe cardiotoxicity leading to arrhythmias and heart failure

Q10. Reserpine is classically isolated from which medicinal plant?

• Digitalis purpurea
• Rauwolfia serpentina
• Atropa belladonna
• Papaver somniferum

Correct Answer: Rauwolfia serpentina

Q11. The chemical conversion of morphine to “heroin” (diacetylmorphine) involves which transformation?

• N-demethylation of the tertiary amine
• Reduction of the 7,8-double bond
• Acetylation of the 3- and 6-hydroxyl groups
• Oxidation of the phenolic ring to a quinone

Correct Answer: Acetylation of the 3- and 6-hydroxyl groups

Q12. Which spectroscopic feature best distinguishes morphine from codeine?

• Morphine shows a strong free phenolic O–H stretch in the IR spectrum absent in codeine
• Codeine has a characteristic nitro-group IR band absent in morphine
• Morphine exhibits a UV absorption at 400 nm not seen in codeine
• Codeine gives a mass spectrum without a molecular ion peak

Correct Answer: Morphine shows a strong free phenolic O–H stretch in the IR spectrum absent in codeine

Q13. Ergot alkaloids responsible for historical outbreaks of ergotism are produced by which fungus?

• Aspergillus flavus
• Claviceps purpurea
• Candida albicans
• Penicillium chrysogenum

Correct Answer: Claviceps purpurea

Q14. A notable central nervous system adverse effect of chronic reserpine therapy is:

• Excessive euphoria
• Severe depression and risk of suicide
• Improved cognitive performance
• Parkinsonian tremor due to dopamine agonism

Correct Answer: Severe depression and risk of suicide

Q15. Which classical alkaloid detection reagent gives a characteristic precipitate with ephedrine during qualitative analysis?

• Biuret reagent
• Benedict’s reagent
• Dragendorff’s reagent
• Ninhydrin reagent

Correct Answer: Dragendorff’s reagent

Q16. Which pharmaceutical salt form of morphine is most commonly used for parenteral administration due to its solubility?

• Morphine base
• Morphine sulfate
• Morphine hydrochloride hemihydrate
• Morphine nitrate

Correct Answer: Morphine sulfate

Q17. Classical ergotism presents clinically in two main forms. What are they?

• Hepatic and renal ergotism
• Gangrenous (vasospastic) and convulsive (neuropsychiatric) ergotism
• Pulmonary and ocular ergotism
• Dermatological and endocrine ergotism

Correct Answer: Gangrenous (vasospastic) and convulsive (neuropsychiatric) ergotism

Q18. The antiparasitic action of emetine is primarily due to which molecular action in protozoa?

• DNA alkylation and strand breakage
• Inhibition of folate synthesis
• Inhibition of protein synthesis by blocking translocation on the ribosome
• Disruption of microtubule polymerization

Correct Answer: Inhibition of protein synthesis by blocking translocation on the ribosome

Q19. For quantitative analysis of reserpine in a formulation, which analytical method and detection wavelength is most appropriate?

• GC–MS with electron capture detection at 400 nm
• HPLC with UV detection at approximately 284 nm
• TLC visualized only under short-wave UV at 254 nm without densitometry
• IR spectroscopy monitoring C=O stretch at 1700 cm–1 only

Correct Answer: HPLC with UV detection at approximately 284 nm

Q20. A convenient laboratory synthesis of racemic ephedrine typically involves which general strategy?

• Pericyclic Diels–Alder reaction between benzene and methylamine
• Oxidative coupling of aniline derivatives followed by hydrolysis
• Reductive amination of phenylacetone (or phenylpropanone) with methylamine followed by stereoselective reduction
• Friedel–Crafts acylation of toluene followed by direct amination

Correct Answer: Reductive amination of phenylacetone (or phenylpropanone) with methylamine followed by stereoselective reduction

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