Introduction: Glycosides in aloes are important phytoconstituents studied in pharmacognosy and B.Pharm curricula. Aloe latex contains anthraquinone glycosides (e.g., aloin, aloe-emodin glycoside) that yield aglycones and sugars on hydrolysis. These compounds exert stimulant laxative activity, have defined toxicities, and are key quality-control markers assessed by TLC, HPLC and chemical tests such as Bornträger’s and Molisch. Understanding classification (O‑ vs C‑glycosides), extraction, hydrolysis, pharmacology, formulation strategies (enteric coating) and standardization is essential for safe and effective pharmaceutical use. This set of MCQs emphasizes phytochemistry, analytical techniques, pharmacology and safety of glycosides from aloes. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What two components make up a glycoside?
- A protein and a lipid
- An aglycone and a sugar
- An acid and an alcohol
- Amino acid and peptide
Correct Answer: An aglycone and a sugar
Q2. Aloin, a principal constituent of aloe latex, is best classified as which type of compound?
- Flavonoid glycoside
- Anthraquinone glycoside
- Saponin glycoside
- Cardiac glycoside
Correct Answer: Anthraquinone glycoside
Q3. What is the primary pharmacological action of anthraquinone glycosides from aloes?
- Antihypertensive effect
- Stimulant laxative action
- Anticoagulant activity
- Beta‑adrenergic blockade
Correct Answer: Stimulant laxative action
Q4. In aloe plants, aloin is concentrated mainly in which anatomical part?
- Inner leaf gel
- Latex (leaf exudate)
- Flower petals
- Root tuber
Correct Answer: Latex (leaf exudate)
Q5. Bornträger’s test is used in pharmacognosy to detect which class of compounds?
- Alkaloids
- Saponins
- Anthraquinones
- Proteins
Correct Answer: Anthraquinones
Q6. Hydrolysis of a glycoside yields which of the following products?
- Only sugars
- Only aglycones
- Sugar and aglycone
- Protein and lipid
Correct Answer: Sugar and aglycone
Q7. What is the main structural difference between O‑glycosides and C‑glycosides?
- O‑glycosides link via oxygen; C‑glycosides link via carbon
- O‑glycosides have peptide bonds; C‑glycosides have ester bonds
- O‑glycosides are proteins; C‑glycosides are lipids
- O‑glycosides are synthetic; C‑glycosides are natural
Correct Answer: O‑glycosides link via oxygen; C‑glycosides link via carbon
Q8. Which analytical technique is most commonly used for precise quantification of aloin in formulations?
- Paper chromatography
- Ultraviolet microscopy
- High‑performance liquid chromatography (HPLC)
- Gravimetric analysis
Correct Answer: High‑performance liquid chromatography (HPLC)
Q9. Aloe‑emodin is best described as which of the following?
- A sugar moiety found in glycosides
- An anthraquinone aglycone
- A fatty acid ester
- An essential oil component
Correct Answer: An anthraquinone aglycone
Q10. Prolonged high‑dose ingestion of aloe anthraquinones can primarily lead to which clinical issue?
- Hyperglycemia
- Electrolyte imbalance (e.g., hypokalemia)
- Increased bone density
- Improved renal function
Correct Answer: Electrolyte imbalance (e.g., hypokalemia)
Q11. The laxative effect of aloe anthraquinones is mainly due to which mechanism?
- Inhibition of acetylcholinesterase in the CNS
- Stimulation of colonic mucosa and increased peristalsis
- Blocking sodium channels in enterocytes
- Increasing bile acid synthesis
Correct Answer: Stimulation of colonic mucosa and increased peristalsis
Q12. Which chemical test detects the carbohydrate portion common to many glycosides?
- Dragendorff’s test
- Murexide test
- Molisch test
- Froth test
Correct Answer: Molisch test
Q13. In Bornträger’s procedure for combined anthraquinone glycosides, which solvent is commonly used to extract the aglycone after hydrolysis?
- Water
- Chloroform
- Acetic acid
- Methanol alone
Correct Answer: Chloroform
Q14. To ensure aloe anthraquinone reaches the colon and reduces upper GI irritation, which formulation approach is appropriate?
- Immediate‑release syrup
- Enteric‑coated tablet targeting intestinal release
- Injectable solution
- Topical cream
Correct Answer: Enteric‑coated tablet targeting intestinal release
Q15. Which constituent is commonly used as a pharmacopoeial marker for standardization of aloe latex?
- Ascorbic acid
- Aloin (barbaloin)
- Citric acid
- Starch
Correct Answer: Aloin (barbaloin)
Q16. Which enzyme class catalyzes the cleavage of glycosidic bonds in vivo?
- Proteases
- Glycosidases
- Lipases
- Oxidoreductases
Correct Answer: Glycosidases
Q17. Compared to HPTLC, HPLC is generally preferred for routine quality control of aloin because it provides:
- Lower sensitivity and poorer reproducibility
- Higher precision and accurate quantitation
- Only qualitative results
- Less selectivity for anthraquinones
Correct Answer: Higher precision and accurate quantitation
Q18. Which of the following is NOT a glycoside typically associated with aloe species?
- Aloin
- Aloe‑emodin glycoside
- Digitoxin
- Aloesin
Correct Answer: Digitoxin
Q19. In Bornträger’s test, what color indicates the presence of anthraquinone derivatives after adding ammonia?
- Blue
- Green
- Pink to red
- Yellow
Correct Answer: Pink to red
Q20. Which part of the aloe leaf is relatively free of anthraquinone glycosides and hence used for topical/edible inner‑gel products?
- Outer cuticle
- Inner leaf gel
- Latex from the pericyclic tubules
- Flower extract
Correct Answer: Inner leaf gel
Q21. Glucose is commonly found as which part of many plant glycosides?
- Aglycone
- Glycone (sugar) moiety
- Enzyme cofactor
- Solvent residue
Correct Answer: Glycone (sugar) moiety
Q22. Which statement is true regarding stability of glycosidic bonds?
- C‑glycosidic bonds are generally more hydrolytically stable than O‑glycosidic bonds
- O‑glycosidic bonds are more stable than C‑glycosidic bonds
- Both bonds have identical stability under all conditions
- Glycosidic bonds cannot be hydrolyzed chemically
Correct Answer: C‑glycosidic bonds are generally more hydrolytically stable than O‑glycosidic bonds
Q23. The term “aglycone” refers to which of the following?
- The sugar portion of a glycoside
- The non‑sugar (active) moiety released after hydrolysis
- A type of polysaccharide
- An amino acid residue
Correct Answer: The non‑sugar (active) moiety released after hydrolysis
Q24. Which anthraquinone aglycone derived from aloe is associated with laxative activity?
- Quercetin
- Aloe‑emodin
- Camphor
- Limonene
Correct Answer: Aloe‑emodin
Q25. During phytochemical extraction of aloe glycosides, which solvent is often used first to defat the crude drug?
- Petroleum ether
- Water
- Acetic acid
- Ethanol 95% (initial step is defatting with nonpolar solvent)
Correct Answer: Petroleum ether
Q26. Regulatory and safety concerns with chronic ingestion of aloe latex glycosides include which of the following?
- Electrolyte disturbances and potential genotoxicity
- Immune suppression only
- Guaranteed long‑term cardiovascular protection
- Complete absence of side effects
Correct Answer: Electrolyte disturbances and potential genotoxicity
Q27. Acid hydrolysis of a plant glycoside primarily results in cleavage of which bond?
- Peptide bond
- Glycosidic bond
- Phosphodiester bond
- Ether bond unrelated to glycoside
Correct Answer: Glycosidic bond
Q28. When formulating water‑rich aloe inner gel, which formulation consideration is most critical?
- Preservation and microbial control
- Inclusion of strong acids to denature proteins
- Removal of all sugars regardless of function
- Avoiding any pH control
Correct Answer: Preservation and microbial control
Q29. To detect combined (bound) anthraquinones present as glycosides, which preparatory step is commonly required before performing Bornträger’s test?
- Direct aqueous extraction without pretreatment
- Hydrolysis (acidic or enzymatic) to liberate aglycones
- Drying at 200 °C
- Protein precipitation with ammonium sulfate
Correct Answer: Hydrolysis (acidic or enzymatic) to liberate aglycones
Q30. Which biological system primarily converts aloe glycosides to their active aglycones after oral ingestion?
- Hepatic cytochrome P450 only
- Colonic (intestinal) microbiota
- Renal glomeruli
- Pulmonary alveoli
Correct Answer: Colonic (intestinal) microbiota
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