Steroids — Dioscorea MCQs With Answer is a focused study resource for B.Pharm students covering steroidal saponins from Dioscorea species, extraction, identification, chemistry and pharmaceutical applications. This introduction emphasizes diosgenin as a key steroidal sapogenin precursor for synthetic corticosteroids and sex hormones, analytical methods (TLC, HPLC, GC‑MS), biosynthesis, and safety/toxicology of saponin‑rich extracts. Expect questions on chemical tests (foam test, Liebermann–Burchard), hydrolysis to release aglycones, chromatographic quantification, and regulatory/pharmaceutical relevance. The content is suited for pharmacognosy, medicinal chemistry and pharmaceutics exam preparation. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which structural description correctly defines the core steroid nucleus?
- Cyclopentanoperhydrophenanthrene ring system
- Benzene fused with pyridine
- Phenylpropanoid backbone
Correct Answer: Cyclopentanoperhydrophenanthrene ring system
Q2. The principal steroidal sapogenin isolated from many Dioscorea species is:
- Diosgenin
- Glycyrrhizin
- Quercetin
- Atropine
Correct Answer: Diosgenin
Q3. Saponins from Dioscorea are primarily classified as which type?
- Steroidal saponins
- Triterpenoid saponins
- Cardiac glycosides
- Alkaloid glycosides
Correct Answer: Steroidal saponins
Q4. The main pharmaceutical importance of diosgenin is as a:
- Starting material for synthetic steroids (e.g., progesterone, cortisone)
- Topical antibacterial agent
- Direct oral contraceptive
- Analgesic alkaloid
Correct Answer: Starting material for synthetic steroids (e.g., progesterone, cortisone)
Q5. Which simple phytochemical test is characteristic for the presence of saponins in a Dioscorea extract?
- Persistent foam (foam test)
- Dragendorff’s test
- Ferric chloride test
- Keller–Kiliani test
Correct Answer: Persistent foam (foam test)
Q6. The Liebermann–Burchard reaction is commonly used to indicate which feature in Dioscorea extracts?
- Unsaturated steroid nucleus (green/blue color)
- Presence of alkaloids (orange color)
- Phenolic hydroxyls (deep purple)
- Sugar moieties (reddish precipitate)
Correct Answer: Unsaturated steroid nucleus (green/blue color)
Q7. To obtain diosgenin from steroidal saponins the usual laboratory procedure is:
- Acid hydrolysis of the glycoside to release the aglycone
- Alkaline oxidation of the sapogenin
- Enzymatic methylation of the sugar
- Neutral extraction with hexane only
Correct Answer: Acid hydrolysis of the glycoside to release the aglycone
Q8. Which solvent is most suitable for initial extraction of steroidal saponins from Dioscorea tubers?
- Methanol (or aqueous ethanol)
- Petroleum ether
- Chloroform alone
- Pure hexane
Correct Answer: Methanol (or aqueous ethanol)
Q9. For reliable quantification of diosgenin in extracts, which analytical technique is preferred?
- High-performance liquid chromatography (HPLC)
- Paper chromatography
- Unmodified gas chromatography
- Simple colorimetric titration
Correct Answer: High-performance liquid chromatography (HPLC)
Q10. Diosgenin belongs to which specific structural subgroup of steroidal sapogenins?
- Spirostane (spirostanol) type
- Cardenolide type
- Triterpenoid oleanane type
- Flavonoid aglycone type
Correct Answer: Spirostane (spirostanol) type
Q11. Acid hydrolysis of steroidal saponins yields which expected products?
- A sugar (glycone) and an aglycone (diosgenin)
- Only free sugars
- Only volatile terpenes
- Pure proteins
Correct Answer: A sugar (glycone) and an aglycone (diosgenin)
Q12. A key biological property of saponin-rich Dioscorea extracts is their ability to:
- Cause hemolysis by interacting with cell membranes
- Act as strong anticholinesterases
- Chelate heavy metals selectively
- Inhibit DNA polymerase directly
Correct Answer: Cause hemolysis by interacting with cell membranes
Q13. Which TLC spray reagent is commonly used to visualize diosgenin and related steroidal sapogenins?
- Anisaldehyde–sulfuric acid reagent
- Dragendorff reagent
- Ninhydrin reagent
- Molisch reagent
Correct Answer: Anisaldehyde–sulfuric acid reagent
Q14. The four fused rings of the steroid nucleus are conventionally labeled as:
- Rings A, B, C and D
- Rings I, II, III and IV
- Alpha, Beta, Gamma and Delta
- Phenyl, Pyran, Furan and Lactone
Correct Answer: Rings A, B, C and D
Q15. In Dioscorea species the highest concentration of diosgenin is typically found in which plant part?
- Tubers or rhizomes
- Leaves
- Flowers
- Seeds
Correct Answer: Tubers or rhizomes
Q16. The immediate isoprene building unit in plant steroid biosynthesis is:
- Isopentenyl pyrophosphate (IPP)
- Shikimic acid
- Chorismic acid
- Malonyl-CoA
Correct Answer: Isopentenyl pyrophosphate (IPP)
Q17. Which reagent and condition are commonly used to cleave glycosidic bonds in steroidal saponins to release sugar and sapogenin?
- Acidic hydrolysis (e.g., dilute HCl under reflux)
- Cold neutral water extraction
- Sodium borohydride reduction at room temperature
- Dry heat pyrolysis
Correct Answer: Acidic hydrolysis (e.g., dilute HCl under reflux)
Q18. Which of the following reagents is NOT useful for detecting or characterizing steroidal sapogenins?
- Dragendorff reagent (specific for alkaloids)
- Anisaldehyde-sulfuric acid
- Liebermann–Burchard reagent
- Foam test for saponins
Correct Answer: Dragendorff reagent (specific for alkaloids)
Q19. Why is derivatization often required before GC–MS analysis of diosgenin?
- Because diosgenin is polar and thermally labile, derivatization increases volatility and stability for GC
- Because GC–MS cannot detect organic compounds without derivatization
- Derivatization decreases molecular weight making ionization easier
- Derivatization converts diosgenin into a sugar
Correct Answer: Because diosgenin is polar and thermally labile, derivatization increases volatility and stability for GC
Q20. A key chemical difference between steroidal and triterpenoid saponins is their carbon skeleton size; steroidal sapogenins are typically:
- Derived from a C27 steroid skeleton
- Derived from a C15 aromatic skeleton
- Always C30 triterpene derivatives
- Peptide‑linked conjugates
Correct Answer: Derived from a C27 steroid skeleton
Q21. Which safety precaution is most important when working with concentrated saponin extracts in the lab?
- Avoid parenteral administration or injection because of hemolytic activity
- They are non‑toxic and require no special precautions
- They are highly radioactive and need shielding
- They will polymerize spontaneously at room temperature
Correct Answer: Avoid parenteral administration or injection because of hemolytic activity
Q22. For HPLC detection of diosgenin, which detector is frequently preferred when the analyte has weak UV absorbance?
- Evaporative light scattering detector (ELSD)
- Conductivity detector
- Flame ionization detector (FID)
- Electrochemical detector
Correct Answer: Evaporative light scattering detector (ELSD)
Q23. Which functional group is characteristic of diosgenin’s aglycone structure?
- Hydroxyl (–OH) groups attached to the steroid skeleton
- Primary amine groups
- Carboxylic acid groups
- Aromatic phenolic rings
Correct Answer: Hydroxyl (–OH) groups attached to the steroid skeleton
Q24. Why is acetylation (e.g., with acetic anhydride) used as a derivatization step before GC analysis of diosgenin?
- To reduce polarity and increase volatility/thermal stability of hydroxyl groups
- To hydrolyze sugar residues selectively
- To introduce a chromophore for UV detection only
- To precipitate unwanted proteins
Correct Answer: To reduce polarity and increase volatility/thermal stability of hydroxyl groups
Q25. Which downstream pharmaceutical steroid has historically been synthesized from diosgenin as a raw material?
- Progesterone
- Aspirin
- Morphine
- Penicillin
Correct Answer: Progesterone
Q26. In infrared spectroscopy of diosgenin, which absorption band is most indicative of hydroxyl groups?
- A broad band around 3200–3600 cm⁻¹
- A sharp band near 1700 cm⁻¹
- Bands at 1600 cm⁻¹ typical for aromatics
- A strong absorption at 2100 cm⁻¹ (alkyne)
Correct Answer: A broad band around 3200–3600 cm⁻¹
Q27. In mass spectrometric analysis of glycosylated saponins, a neutral loss of ~162 Da typically corresponds to cleavage of:
- A hexose sugar (e.g., glucose)
- Water molecule
- Carbon dioxide
- A sulfate group
Correct Answer: A hexose sugar (e.g., glucose)
Q28. Which Dioscorea species is commonly referenced as a traditional source of diosgenin and used in herbal preparations?
- Dioscorea villosa (wild yam)
- Dioscorea trifida only
- Dioscorea bulbifera exclusively for alkaloids
- Dioscorea lotus for flavonoids only
Correct Answer: Dioscorea villosa (wild yam)
Q29. A simple bioassay to estimate saponin potency in an extract is:
- Red blood cell (RBC) hemolysis assay
- Minimum inhibitory concentration against E. coli only
- pH titration curve analysis
- Color change with iodine solution
Correct Answer: Red blood cell (RBC) hemolysis assay
Q30. Regarding regulatory and pharmaceutical use, diosgenin is best described as:
- A raw starting material/precursor that requires chemical conversion to approved steroid drugs
- An FDA‑approved oral estrogenic drug used directly without modification
- A controlled narcotic precursor regulated like opiates
- A preservative additive in parenteral formulations
Correct Answer: A raw starting material/precursor that requires chemical conversion to approved steroid drugs
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