Introduction: Secondary metabolites are diverse bioactive phytochemicals—alkaloids, terpenoids, flavonoids, phenolics, glycosides and polyketides—produced by plants, microbes and marine organisms. These compounds arise from biosynthetic routes such as shikimate, polyketide, mevalonate (MVA) and non-mevalonate (MEP) pathways and are crucial in pharmacognosy and drug discovery. For B.Pharm students, understanding their chemical classes, biosynthesis, pharmacological roles, extraction, analytical techniques (TLC, HPLC), identification tests and examples like morphine, quinine, artemisinin and paclitaxel is essential for quality control and formulation. This concise, exam-focused review links theory to clinical relevance and analytical practice. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which biosynthetic pathway is primarily responsible for the formation of aromatic amino acids and many phenolic secondary metabolites?
- Mevalonate (MVA) pathway
- Shikimate pathway
- Nonribosomal peptide pathway
- Polyketide pathway
Correct Answer: Shikimate pathway
Q2. Alkaloids are characterized chemically by the presence of which element in their structure?
- Sulfur
- Nitrogen
- Phosphorus
- Chlorine
Correct Answer: Nitrogen
Q3. Which of the following drugs is a diterpenoid originally isolated from Taxus species?
- Artemisinin
- Morphine
- Paclitaxel (Taxol)
- Quinine
Correct Answer: Paclitaxel (Taxol)
Q4. The mevalonate (MVA) pathway predominantly supplies precursors for which class of secondary metabolites?
- Alkaloids
- Terpenoids (isoprenoids)
- Flavonoids
- Polyketides
Correct Answer: Terpenoids (isoprenoids)
Q5. Which qualitative reagent is commonly used to detect alkaloids in plant extracts?
- Ferric chloride
- Dragendorff’s reagent
- Salkowski reagent
- Shinoda reagent
Correct Answer: Dragendorff’s reagent
Q6. Flavonoids share which basic carbon skeleton?
- C6–C1
- C6–C3–C6
- C5 isoprene units
- C14 polyketide chain
Correct Answer: C6–C3–C6
Q7. Which technique is most suitable for quantitative analysis and purity assessment of a marker secondary metabolite?
- Thin layer chromatography (TLC)
- Ultraviolet-visible spectroscopy (UV-Vis)
- High-performance liquid chromatography (HPLC)
- Paper chromatography
Correct Answer: High-performance liquid chromatography (HPLC)
Q8. Which enzyme complex is mainly responsible for the biosynthesis of polyketide secondary metabolites?
- Polyketide synthase (PKS)
- Nonribosomal peptide synthetase (NRPS)
- Terpene synthase
- Aromatic aminotransferase
Correct Answer: Polyketide synthase (PKS)
Q9. Artemisinin is classified as which type of secondary metabolite?
- Sesquiterpene lactone
- Alkaloid
- Flavonoid glycoside
- Anthraquinone
Correct Answer: Sesquiterpene lactone
Q10. Which pathway typically operates in plastids and is also called the non-mevalonate pathway?
- Shikimate pathway
- MEP (DOXP) pathway
- MVA pathway
- Polyketide pathway
Correct Answer: MEP (DOXP) pathway
Q11. Which of the following is a common storage form of secondary metabolites in plants?
- Vacuoles and resin ducts
- Mitochondria
- Nucleus
- Ribosomes
Correct Answer: Vacuoles and resin ducts
Q12. Which test gives a color change with phenolic compounds such as tannins?
- Borntrager’s test
- Salkowski test
- Ferric chloride test
- Biuret test
Correct Answer: Ferric chloride test
Q13. Nonribosomal peptide synthetases (NRPS) are primarily involved in biosynthesis of which microbial secondary metabolites?
- Terpenoids
- Polyketides only
- Peptide antibiotics like vancomycin
- Flavonoids
Correct Answer: Peptide antibiotics like vancomycin
Q14. Which solvent is most appropriate for extracting polar glycosides from plant material?
- Hexane
- Methanol or aqueous methanol
- Chloroform
- Pentane
Correct Answer: Methanol or aqueous methanol
Q15. Which secondary metabolite class commonly acts as phytoalexins—antimicrobial compounds produced in response to pathogen attack?
- Primary metabolites like sugars
- Phytohormones exclusively
- Phenolics and terpenoids
- Structural polysaccharides
Correct Answer: Phenolics and terpenoids
Q16. Which chromatographic visualization reagent is commonly used to detect terpene and steroid spots on TLC?
- Dragendorff’s reagent
- ninhydrin
- Liebermann–Burchard reagent
- Molisch’s reagent
Correct Answer: Liebermann–Burchard reagent
Q17. Quinoline alkaloid quinine, historically used as an antimalarial, is obtained from which genus?
- Taxus
- Cinchona
- Digitalis
- Papaver
Correct Answer: Cinchona
Q18. Which analytical parameter is essential for herbal drug standardization and quantifies inorganic contamination?
- Ash values
- Boiling point
- Optical rotation
- Viscosity
Correct Answer: Ash values
Q19. Which structural feature defines cardiac glycosides like digoxin?
- Peptide backbone with nonproteinogenic amino acids
- Sugar moiety attached to a steroidal aglycone
- Multiple isoprene units only
- Quinone nucleus without sugar
Correct Answer: Sugar moiety attached to a steroidal aglycone
Q20. Which microbial genus is well known for producing many clinically important antibiotics such as streptomycin?
- Escherichia
- Streptomyces
- Clostridium
Correct Answer: Streptomyces
Q21. Which class of enzymes introduces oxygen into hydrophobic secondary metabolites to increase polarity?
- Transferases only
- Oxidoreductases (e.g., cytochrome P450 monooxygenases)
- Ligases
- Isomerases
Correct Answer: Oxidoreductases (e.g., cytochrome P450 monooxygenases)
Q22. Which technique is most useful for preliminary fingerprinting of herbal extracts to compare batches?
- NMR spectroscopy only
- TLC fingerprinting
- Mass spectrometry without separation
- pH testing
Correct Answer: TLC fingerprinting
Q23. Which of the following best describes a glycoside?
- An aglycone molecule bound to a sugar moiety
- A peptide linked to a lipid
- A terpene dimer without sugars
- An alkaloid lacking nitrogen
Correct Answer: An aglycone molecule bound to a sugar moiety
Q24. Which of the following secondary metabolites is a benzylisoquinoline alkaloid used as an analgesic?
- Atropine
- Morphine
- Caffeine
- Reserpine
Correct Answer: Morphine
Q25. Elicitors applied in plant tissue culture are used to:
- Suppress secondary metabolite synthesis
- Stimulate production of specific secondary metabolites
- Convert secondary metabolites into primary metabolites
- Sterilize the culture medium
Correct Answer: Stimulate production of specific secondary metabolites
Q26. Which structural unit is the basic isoprene-derived building block for terpenoids?
- Acetyl-CoA
- Isopentenyl diphosphate (IPP)
- Shikimic acid
- Malonyl-CoA
Correct Answer: Isopentenyl diphosphate (IPP)
Q27. Borntrager’s test is typically used for detecting which class of compounds?
- Anthraquinone glycosides
- Alkaloids
- Terpenes
- Steroids
Correct Answer: Anthraquinone glycosides
Q28. Which factor most strongly influences the distribution of secondary metabolites within a plant?
- Photosynthetic rate only
- Genetics and tissue-specific expression
- Soil pH exclusively
- Color of flowers only
Correct Answer: Genetics and tissue-specific expression
Q29. Which secondary metabolite class commonly provides UV protection and antioxidant activity in plants and human nutraceuticals?
- Polysaccharides
- Flavonoids
- Inorganic salts
- Proteins
Correct Answer: Flavonoids
Q30. For acid-base extraction of alkaloids from plant material, which pH adjustment helps transfer alkaloids into organic solvent as free bases?
- Strongly acidic pH (~1)
- Neutral pH (~7)
- Alkaline pH (>9)
- Exactly pH 5
Correct Answer: Alkaline pH (>9)
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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