Introduction: Biological evaluation of crude drugs is a core subject for B.Pharm students, focusing on pharmacological screening, toxicity studies, and standardization of herbal materials. This topic covers in vivo and in vitro bioassays, acute and chronic toxicity testing, LD50/ED50 determination, antimicrobial assays (MIC, MBC), cytotoxicity (MTT, brine shrimp), genotoxicity (Ames test), and bioassay-guided fractionation. Understanding quality control, potency estimation, reproducibility, and OECD guidelines ensures safe, effective crude drug development. Keywords: biological evaluation, crude drugs, bioassays, toxicity studies, pharmacological screening, standardization, B.Pharm. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which of the following best defines ‘biological evaluation’ of crude drugs?
- Chemical fingerprinting of plant extracts
- Assessment of pharmacological activity and safety using in vitro and in vivo models
- Spectroscopic identification of active compounds
- Quantitative estimation of heavy metals
Correct Answer: Assessment of pharmacological activity and safety using in vitro and in vivo models
Q2. What is the primary purpose of an LD50 study in crude drug evaluation?
- Determine minimum effective dose
- Estimate acute oral toxicity that kills 50% of test animals
- Measure long-term carcinogenic potential
- Evaluate antimicrobial potency
Correct Answer: Estimate acute oral toxicity that kills 50% of test animals
Q3. Which in vitro assay is commonly used to screen general cytotoxicity of plant extracts?
- Agar diffusion
- MTT assay
- Ophthalmic irritation test
- ED50 determination
Correct Answer: MTT assay
Q4. In antimicrobial testing of crude drugs, MIC stands for:
- Maximum inhibitory concentration
- Minimum inhibitory concentration
- Microbial inhibitory count
- Minimum infectious concentration
Correct Answer: Minimum inhibitory concentration
Q5. Which bioassay is most appropriate for preliminary cytotoxic screening using small, inexpensive organisms?
- Rodent chronic toxicity
- Brine shrimp lethality assay
- Human clinical trial
- Patch test
Correct Answer: Brine shrimp lethality assay
Q6. Bioassay-guided fractionation is used primarily to:
- Quantify total extract yield
- Identify and isolate active constituents based on biological activity
- Standardize chromatographic methods
- Determine acute toxicity only
Correct Answer: Identify and isolate active constituents based on biological activity
Q7. The Ames test is designed to detect which property of a crude drug?
- Antimicrobial activity
- Mutagenic potential / genotoxicity
- Hepatoprotective effect
- Anti-inflammatory activity
Correct Answer: Mutagenic potential / genotoxicity
Q8. Which guideline series is commonly followed for toxicity testing of herbal extracts?
- ICH guidelines for stability only
- OECD guidelines for toxicity testing
- USP monographs exclusively
- WHO Good Agricultural Practices
Correct Answer: OECD guidelines for toxicity testing
Q9. What does ED50 represent in pharmacological screening?
- Effective dose in 50% of a population
- Estimated dose causing death in 50% animals
- Extra dose required for 50% increase in potency
- Electrodiagnostic value at 50 Hz
Correct Answer: Effective dose in 50% of a population
Q10. Which test would you use to assess anti-inflammatory activity of a crude drug in vivo?
- Hot plate test
- Carrageenan-induced paw edema test
- Agar dilution method
- MTT cytotoxicity assay
Correct Answer: Carrageenan-induced paw edema test
Q11. In agar diffusion antimicrobial assays, the zone of inhibition indicates:
- Solubility of extract
- Antimicrobial activity against the test organism
- pH of the medium
- Viscosity of the extract
Correct Answer: Antimicrobial activity against the test organism
Q12. Which parameter best describes the safety margin of a crude drug?
- Solubility index
- Therapeutic index
- Retention factor (Rf)
- Chromatographic purity
Correct Answer: Therapeutic index
Q13. Which of the following is a measure of acute oral toxicity classification?
- ED100
- LD50
- MIC
- Log P value
Correct Answer: LD50
Q14. TLC bioautography combines thin-layer chromatography with:
- Mass spectrometry
- Biological activity detection on chromatogram
- Infrared spectroscopy
- HPLC gradient elution
Correct Answer: Biological activity detection on chromatogram
Q15. Which in vitro assay assesses pro-oxidant or antioxidant potential of crude extracts?
- DPPH radical scavenging assay
- Brine shrimp lethality
- Hot plate analgesic test
- Carrageenan edema
Correct Answer: DPPH radical scavenging assay
Q16. What is the role of positive and negative controls in bioassays?
- Only for regulatory documentation
- Ensure assay validity, sensitivity and specificity
- Increase sample throughput
- Reduce the need for replicates
Correct Answer: Ensure assay validity, sensitivity and specificity
Q17. Which assay is commonly used to detect antiulcer activity in animal models?
- HCl-ethanol induced ulcer model
- Ames test
- Disk diffusion assay
- In vitro COX inhibition only
Correct Answer: HCl-ethanol induced ulcer model
Q18. Bioavailability assessment of a crude drug primarily involves:
- Measuring topical potency in vitro
- Determining the extent and rate of active constituent absorption
- Estimating MIC against pathogens
- Qualitative phytochemical screening only
Correct Answer: Determining the extent and rate of active constituent absorption
Q19. Which toxicological endpoint assesses long-term cancer-causing potential?
- Acute oral LD50
- Carcinogenicity study
- MTT cytotoxicity
- MIC determination
Correct Answer: Carcinogenicity study
Q20. Which method assesses enzyme inhibition (e.g., COX, acetylcholinesterase) by crude extracts?
- Receptor binding assay
- Enzyme inhibition assay using purified enzyme or homogenate
- Brine shrimp lethality
- Patch test
Correct Answer: Enzyme inhibition assay using purified enzyme or homogenate
Q21. Which practice is essential when reporting biological evaluation results to ensure reproducibility?
- Omitting solvent details
- Providing detailed methods, controls, doses and statistical analysis
- Reporting only positive findings
- Using only single animal per group
Correct Answer: Providing detailed methods, controls, doses and statistical analysis
Q22. Which assay is suitable to evaluate anti-diarrheal activity in rodents?
- Castor oil-induced diarrhea model
- MTT assay
- Disk diffusion test
- Ames test
Correct Answer: Castor oil-induced diarrhea model
Q23. Which is a key ethical principle in animal-based biological evaluation?
- Use as many animals as possible
- Apply the 3Rs: Replace, Reduce, Refine
- Skip approval processes to save time
- Use only historical controls
Correct Answer: Apply the 3Rs: Replace, Reduce, Refine
Q24. Which analytical approach helps correlate biological activity with specific phytochemicals?
- Bioassay-guided fractionation combined with chromatographic and spectroscopic identification
- Measuring extract pH only
- Random animal feeding studies without analysis
- Thin-layer chromatography without activity testing
Correct Answer: Bioassay-guided fractionation combined with chromatographic and spectroscopic identification
Q25. Which test is typically used to screen mutagenicity using bacteria with histidine requirement?
- MTT assay
- Ames test
- Brine shrimp assay
- Carrageenan assay
Correct Answer: Ames test
Q26. Which parameter indicates bactericidal rather than bacteriostatic activity?
- MIC lower than MBC
- MBC equal to or close to MIC (within 1–2 dilutions)
- Large zone of inhibition only
- High IC50 in enzyme assay
Correct Answer: MBC equal to or close to MIC (within 1–2 dilutions)
Q27. Which in vivo model is widely used for analgesic screening of crude extracts?
- Hot plate and tail-flick tests
- Agar diffusion
- MTT cytotoxicity
- Brine shrimp lethality only
Correct Answer: Hot plate and tail-flick tests
Q28. What is the advantage of using in vitro assays early in crude drug evaluation?
- They always replace in vivo studies
- Speed, lower cost, reduced animal use and mechanistic insights
- They guarantee clinical efficacy
- They measure chronic toxicity better than animal studies
Correct Answer: Speed, lower cost, reduced animal use and mechanistic insights
Q29. Which parameter is essential while reporting MIC values for microbial assays?
- Solvent color
- Exact organism strain, inoculum size, medium and incubation conditions
- Only the brand of petri plate
- Number of researchers involved
Correct Answer: Exact organism strain, inoculum size, medium and incubation conditions
Q30. Standardization of crude drugs by biological evaluation helps to:
- Ignore batch-to-batch variability
- Ensure consistent therapeutic potency and safety across batches
- Eliminate need for chemical analysis
- Reduce documentation requirements
Correct Answer: Ensure consistent therapeutic potency and safety across batches
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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