Detection of phototoxins in herbal drugs MCQs With Answer

Introduction: Detection of phototoxins in herbal drugs MCQs With Answer is designed for M.Pharm students specializing in Herbal and Cosmetic Analysis. This collection covers fundamental principles, photochemical mechanisms, common herbal phototoxins (e.g., furocoumarins, hypericins), sample preparation, chromatographic and spectroscopic detection techniques (HPLC-PDA, LC-MS/MS, UV-Vis, fluorescence), photobiological assays (e.g., OECD TG 432 3T3 NRU), singlet oxygen and ROS detection, and validation parameters like limits of detection and matrix effects. The questions emphasize analytical strategy, regulatory guidance, and interpretation of phototoxicity data so students gain both theoretical understanding and practical insight into detecting and characterizing phototoxins in herbal matrices.

Q1. Which class of compounds is most commonly associated with phototoxic reactions in many herbal remedies and is typically screened for in phototoxin analysis?

• Alkaloids such as morphine
• Furocoumarins (psoralens) like bergapten and methoxsalen
• Monoterpenes such as limonene
• Polysaccharides such as mucilage

Correct Answer: Furocoumarins (psoralens) like bergapten and methoxsalen

Q2. Which in vitro guideline test is internationally accepted for primary phototoxicity screening of chemicals and herbal extracts?

• OECD TG 429 (Skin Sensitisation)
• OECD TG 437 (Bacterial Reverse Mutation)
• OECD TG 432 (3T3 Neutral Red Uptake Phototoxicity Test)
• OECD TG 410 (Repeated Dose 28-day Toxicity)

Correct Answer: OECD TG 432 (3T3 Neutral Red Uptake Phototoxicity Test)

Q3. In the 3T3 NRU phototoxicity test, which parameter is commonly used to express phototoxic potential?

• Skin irritation index
• Photoirritation Factor (PIF) calculated from EC50 values
• Transdermal flux (µg/cm2/hr)
• Minimal erythema dose (MED) only

Correct Answer: Photoirritation Factor (PIF) calculated from EC50 values

Q4. Which analytical technique provides both separation and spectral information useful to identify photoreactive constituents by their characteristic UVA-visible absorption?

• Gas chromatography with flame ionization detector (GC-FID)
• High performance liquid chromatography with photodiode array detection (HPLC-PDA)
• Gravimetric analysis
• Capillary electrophoresis without UV detector

Correct Answer: High performance liquid chromatography with photodiode array detection (HPLC-PDA)

Q5. Which photophysical mechanism involves energy transfer from an excited photosensitizer to molecular oxygen producing singlet oxygen (1O2)?

• Type III photochemistry
• Type I (radical-mediated) mechanism
• Type II (energy transfer) mechanism
• Direct thermal decomposition

Correct Answer: Type II (energy transfer) mechanism

Q6. Which reagent is commonly used as a chemical probe to detect singlet oxygen generation in phototoxicity assays?

• 2,2-Diphenyl-1-picrylhydrazyl (DPPH)
• 1,3-Diphenylisobenzofuran (DPBF)
• Biuret reagent
• Ninhydrin

Correct Answer: 1,3-Diphenylisobenzofuran (DPBF)

Q7. Which instrumental technique is most suitable for structural confirmation of trace phototoxins in complex herbal extracts?

• LC-MS/MS (liquid chromatography-tandem mass spectrometry)
• Refractometry
• Paper chromatography
• Polarimetry

Correct Answer: LC-MS/MS (liquid chromatography-tandem mass spectrometry)

Q8. When preparing herbal samples for phototoxin screening, which precaution is most important to prevent artifact formation or loss of photoreactive compounds?

• Exposure to strong UV light during extraction
• Performing extraction and storage under dim light and using amber glass
• Drying samples at high temperature (>120°C)
• Using reactive metal containers

Correct Answer: Performing extraction and storage under dim light and using amber glass

Q9. Which spectral property is most indicative that a compound may act as a photosensitizer under UVA exposure?

• Strong absorbance in the infrared (>700 nm)
• Strong absorbance in the UVA-visible region (320–400 nm) with high molar extinction coefficient
• Absence of any chromophore
• Only fluorescence in the UV-C range (<280 nm)

Correct Answer: Strong absorbance in the UVA-visible region (320–400 nm) with high molar extinction coefficient

Q10. Which herbal constituent from St. John’s wort is primarily implicated in photodynamic activity and can be detected by spectroscopic methods?

• Hypericin
• Salicin
• Ginsenoside Rb1
• Curcumin

Correct Answer: Hypericin

Q11. Which phototoxicity index is calculated as EC50 without irradiation divided by EC50 with irradiation in an in vitro assay?

• Partition coefficient (log P)
• Photoirritation Factor (PIF)
• Photostability ratio (PSR)
• Skin absorption ratio

Correct Answer: Photoirritation Factor (PIF)

Q12. Which measurement technique directly detects free radical species generated by photoexcited samples using spin trapping?

• UV-Vis spectrophotometry
• Electron spin resonance (ESR) spectroscopy
• Luminescence plate assay without probes
• Reversed-phase thin layer chromatography (TLC)

Correct Answer: Electron spin resonance (ESR) spectroscopy

Q13. For chromatographic fingerprinting of phototoxins, which detector combination helps correlate chromatographic peaks with photoreactivity?

• ELSD only
• HPLC coupled with photodiode array (PDA) and MS
• GC-FID only
• Refractive index detector alone

Correct Answer: HPLC coupled with photodiode array (PDA) and MS

Q14. Which of the following is a correct interpretation when an herbal extract shows PIF > 5 in the 3T3 NRU phototoxicity test?

• The extract is conclusively photoprotective
• The extract has significant phototoxic potential
• The extract is non-phototoxic and safe for unrestricted topical use
• PIF does not provide any phototoxic information

Correct Answer: The extract has significant phototoxic potential

Q15. Which light source is typically used to mimic solar UVA/visible exposure during phototoxicity testing of herbal samples?

• Mercury vapor lamp emitting only UV-C
• Xenon arc solar simulator with appropriate filters
• Lamp emitting strictly at 254 nm

Correct Answer: Xenon arc solar simulator with appropriate filters

Q16. Which assay detects intracellular oxidative stress induced by photoactivated compounds using a fluorescent probe?

• Neutral red uptake without irradiation
• DCF-DA (2′,7′-dichlorodihydrofluorescein diacetate) ROS assay
• Kjeldahl nitrogen assay
• Bradford protein assay

Correct Answer: DCF-DA (2′,7′-dichlorodihydrofluorescein diacetate) ROS assay

Q17. In method validation for detecting phototoxins, which parameter assesses whether matrix components influence analyte signal in LC-MS analyses?

• Limit of detection (LOD)
• Matrix effect evaluation
• pH stability only
• Thin layer chromatographic Rf reproducibility

Correct Answer: Matrix effect evaluation

Q18. Which thin-layer chromatography visualization technique can help reveal furocoumarins after separation?

• Visualizing under long-wave UV (365 nm) and comparing fluorescence/quenching
• Exposure to iodine vapors only
• Heat charring at 300°C
• Staining with ninhydrin

Correct Answer: Visualizing under long-wave UV (365 nm) and comparing fluorescence/quenching

Q19. Which photostability parameter should be controlled during assay of phototoxins to ensure reproducible irradiation conditions?

• Ambient humidity only
• Irradiance (W/m2) and exposure duration with spectral distribution
• Solvent boiling point at extraction
• Room temperature color

Correct Answer: Irradiance (W/m2) and exposure duration with spectral distribution

Q20. Which statement best describes the role of photodiode array detection in screening herbal extracts for phototoxic compounds?

• PDA provides only mass information without UV spectra
• PDA records UV-Vis spectra across peaks enabling identification of compounds absorbing in UVA-visible region linked to photoreactivity
• PDA is irrelevant for phototoxin analysis and should not be used
• PDA measures only fluorescence intensity at a single wavelength

Correct Answer: PDA records UV-Vis spectra across peaks enabling identification of compounds absorbing in UVA-visible region linked to photoreactivity

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