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DOH Pharmacist Exam study materials
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DOH Pharmacist Exam practice questions

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Question 1Pharmaceutical Chemistry and Medicinal Chemistry

Which functional group is characteristic of a carboxylic acid?

  1. -CHO
  2. -OH
  3. -COOH Correct answer.
  4. -CO-

Explanation

A carboxylic acid contains a carbonyl carbon bonded to a hydroxyl group, written -COOH. The carbonyl and hydroxyl are on the same carbon, which distinguishes it from an alcohol or aldehyde.

Question 2Pharmaceutical Chemistry and Medicinal Chemistry

A drug is a weak base with pKa 8.4. In plasma at pH 7.4, the predominant species is:

  1. the ionized conjugate acid form Correct answer.
  2. an equal mixture of both forms
  3. the un-ionized free base
  4. a covalently bound adduct

Explanation

For a weak base, when pH is below the pKa the protonated (ionized conjugate acid) form predominates. Since 7.4 < 8.4, the ionized form dominates by roughly a 10:1 ratio.

Question 3Pharmaceutical Chemistry and Medicinal Chemistry

Which statement best describes a prodrug?

  1. A formulation that releases drug by osmosis
  2. A drug that binds irreversibly to its receptor
  3. A chemically modified agent converted in the body to the active drug Correct answer.
  4. An inactive metabolite excreted unchanged

Explanation

A prodrug is a pharmacologically inactive derivative that undergoes biotransformation in vivo to release the active parent compound, often to improve absorption or stability.

Question 4Pharmaceutical Chemistry and Medicinal Chemistry

The benzene ring in a drug molecule is best classified as which type of structural feature?

  1. an aliphatic heterocycle
  2. a linear conjugated chain
  3. an aromatic carbocycle Correct answer.
  4. a saturated alicyclic ring

Explanation

Benzene is a six-membered carbocyclic ring with a fully conjugated pi system satisfying Huckel aromaticity. It contains no heteroatoms and is not saturated.

Question 5Pharmaceutical Chemistry and Medicinal Chemistry

Which phase of drug metabolism is primarily associated with conjugation reactions such as glucuronidation?

  1. Phase II Correct answer.
  2. Phase I
  3. Phase 0
  4. Phase III

Explanation

Phase II metabolism involves conjugation, attaching polar groups such as glucuronic acid, sulfate, or glutathione to increase water solubility for excretion. Phase I reactions are oxidation, reduction, and hydrolysis.

Question 6Pharmaceutical Chemistry and Medicinal Chemistry

Which structural feature of penicillin is essential for its antibacterial activity?

  1. the carboxyl group alone
  2. the beta-lactam ring Correct answer.
  3. the phenyl side chain
  4. the thiazolidine ring alone

Explanation

The strained beta-lactam ring is the reactive acylating group that binds bacterial transpeptidases. Its integrity is required for activity, and opening it abolishes antibacterial action.

Question 7Pharmaceutical Chemistry and Medicinal Chemistry

Which physicochemical property most directly predicts that a drug will passively diffuse across a lipid membrane?

  1. high degree of ionization
  2. high aqueous solubility at pH 7
  3. large polar surface area
  4. low molecular weight and moderate lipophilicity Correct answer.

Explanation

Passive transcellular diffusion favors small, moderately lipophilic, largely un-ionized molecules. High polarity or ionization hinders membrane permeation.

Question 8Pharmaceutical Chemistry and Medicinal Chemistry

What is the primary purpose of the Lipinski Rule of Five?

  1. To determine receptor binding affinity
  2. To calculate the elimination half-life
  3. To predict oral bioavailability from simple molecular properties Correct answer.
  4. To design prodrugs

Explanation

The Rule of Five uses molecular weight, logP, hydrogen bond donors/acceptors, and polar surface area to flag likely poor oral absorption. It is a heuristic for oral bioavailability, not for potency or kinetics.

Question 9Pharmaceutical Chemistry and Medicinal Chemistry

A drug has a pKa of 3.5 as a weak acid. In the stomach at pH 1.5, what fraction is approximately un-ionized?

  1. about 10%
  2. about 99% Correct answer.
  3. about 50%
  4. about 1%

Explanation

For a weak acid, when pH is well below the pKa, the un-ionized form predominates. With a 2-unit pH-pKa difference, the ratio of un-ionized to ionized is about 100:1, so roughly 99% is un-ionized.

Question 10Pharmaceutical Chemistry and Medicinal Chemistry

Which amino acid residue is most commonly involved in forming a covalent enzyme-inhibitor bond with aspirin in cyclooxygenase?

  1. serine Correct answer.
  2. histidine
  3. cysteine
  4. lysine

Explanation

Aspirin acetylates a serine residue in the active site of cyclooxygenase, irreversibly blocking prostaglandin synthesis. This covalent acetylation is the basis of its antiplatelet effect.

Question 11Pharmaceutical Chemistry and Medicinal Chemistry

Which of the following best explains why a quaternary ammonium compound generally has poor oral absorption?

  1. It has an excessively high logP
  2. It is rapidly glucuronidated in the gut
  3. It is too small to be absorbed
  4. It is permanently charged and cannot passively cross membranes Correct answer.

Explanation

A quaternary ammonium nitrogen carries a permanent positive charge regardless of pH, so the molecule cannot adopt an un-ionized form for passive transcellular diffusion. Absorption is therefore limited.

Question 12Pharmaceutical Chemistry and Medicinal Chemistry

Which reaction type is characteristic of cytochrome P450 enzymes in Phase I metabolism?

  1. Hydrolysis of amide bonds only
  2. Conjugation with glucuronic acid
  3. Reduction of disulfide bonds only
  4. Oxidation of lipophilic substrates Correct answer.

Explanation

Cytochrome P450 monooxygenases catalyze oxidative reactions, inserting oxygen into substrates to increase polarity. Conjugation is a Phase II process, and P450s are not limited to reduction or hydrolysis.

Question 13Pharmaceutical Chemistry and Medicinal Chemistry

A structure-activity relationship study shows that adding a methyl group to a lead compound increases potency tenfold. What does this indicate?

  1. The methyl group formed a covalent bond
  2. The compound became more hydrophilic
  3. The receptor has a small hydrophobic pocket accommodating the methyl group Correct answer.
  4. The compound lost its pharmacophore

Explanation

A potency increase from a small alkyl addition suggests favorable hydrophobic contact within a defined receptor pocket. This is a classic SAR observation of steric and lipophilic complementarity.

Question 14Pharmaceutical Chemistry and Medicinal Chemistry

Which property of a drug is most directly measured by its logP value?

  1. Its metabolic rate
  2. Its receptor affinity
  3. Its partition between octanol and water Correct answer.
  4. Its plasma protein binding

Explanation

logP is the logarithm of the partition coefficient of a neutral compound between octanol (lipid surrogate) and water. It quantifies intrinsic lipophilicity.

Question 15Pharmaceutical Chemistry and Medicinal Chemistry

In the design of a bioisostere replacement, replacing an oxygen atom of a carboxylic acid with what group commonly gives an acidic but more metabolically stable isostere?

  1. a tetrazole ring Correct answer.
  2. a methyl group
  3. a hydroxyl group
  4. an amine

Explanation

Tetrazole is a classic carboxylic acid bioisostere: it is acidic at physiological pH and resists metabolism while maintaining hydrogen bonding. Methyl, amine, and hydroxyl replacements do not reproduce the acidity.

Question 16Pharmaceutical Chemistry and Medicinal Chemistry

Which statement about enantiomers of a chiral drug is correct?

  1. They have identical pharmacological activity in all cases
  2. They always interconvert rapidly in plasma
  3. They differ only in molecular weight
  4. They may differ in receptor affinity and metabolic fate Correct answer.

Explanation

Enantiomers have identical physicochemical properties in achiral environments but can differ markedly in binding to chiral receptors and in enzyme-mediated metabolism. This underlies the development of single-enantiomer drugs.

Question 17Pharmaceutical Chemistry and Medicinal Chemistry

Which structural modification most reliably increases the aqueous solubility of a poorly soluble lead compound?

  1. Introducing an ionizable group such as a carboxylic acid Correct answer.
  2. Increasing the number of aromatic rings
  3. Adding a bulky tert-butyl group
  4. Adding a lipophilic alkyl chain

Explanation

Introducing an ionizable group allows the molecule to exist in a charged, water-soluble form at physiological pH. Lipophilic additions generally reduce aqueous solubility.

Question 18Pharmaceutical Chemistry and Medicinal Chemistry

A patient takes drug A, which is metabolized by CYP3A4. Coadministration of a potent CYP3A4 inhibitor is expected to:

  1. increase plasma levels of drug A Correct answer.
  2. increase renal clearance of drug A
  3. decrease plasma levels of drug A
  4. have no effect on drug A

Explanation

Inhibiting the enzyme that clears drug A reduces its metabolism, raising plasma concentrations and the risk of toxicity. This is a classic metabolic drug-drug interaction.

Question 19Pharmaceutical Chemistry and Medicinal Chemistry

Which of the following is the most likely consequence of a strong electron-withdrawing group placed para to a phenolic hydroxyl on a drug molecule?

  1. Decreased acidity of the phenol
  2. Increased acidity of the phenol Correct answer.
  3. Formation of a quaternary ammonium center
  4. Loss of aromaticity

Explanation

Electron-withdrawing groups stabilize the phenoxide anion by delocalizing negative charge, lowering the pKa and increasing acidity. This can alter ionization and receptor interactions.

Question 20Pharmaceutical Chemistry and Medicinal Chemistry

Which drug-metabolizing reaction is catalyzed by esterases acting on a prodrug ester?

  1. Hydrolysis Correct answer.
  2. Methylation
  3. Glucuronidation
  4. Oxidation

Explanation

Esterases catalyze hydrolysis of ester bonds, cleaving the prodrug to release the active acid and alcohol. This is a common activation route for ester prodrugs.

Question 21Pharmaceutical Chemistry and Medicinal Chemistry

A lead compound shows high potency in vitro but poor oral bioavailability. Adding a polar ionizable group improves solubility but reduces membrane permeability. Which principle best describes this trade-off?

  1. The Michaelis-Menten equation
  2. The lock-and-key receptor model
  3. The rule of five balance between solubility and permeability Correct answer.
  4. The Henderson-Hasselbalch equation

Explanation

The rule-of-five framework captures the balance between aqueous solubility and membrane permeability; improving one often compromises the other. Optimal drug design seeks a compromise within acceptable property ranges.

Question 22Pharmaceutical Chemistry and Medicinal Chemistry

Which mechanism explains why a suicide inhibitor permanently inactivates its target enzyme?

  1. Allosteric binding that alters substrate affinity
  2. Enzyme-catalyzed conversion to a reactive species that covalently binds the enzyme Correct answer.
  3. Chelation of a metal cofactor
  4. Reversible competitive occupancy of the active site

Explanation

A suicide (mechanism-based) inhibitor is processed by the enzyme into a reactive intermediate that covalently modifies the active site, causing irreversible inactivation. This requires catalytic turnover for activation.

Question 23Pharmaceutical Chemistry and Medicinal Chemistry

A molecule contains a carboxylic acid (pKa 4.5) and a basic amine (pKa 9.0). At pH 7.4, which statement is correct?

  1. The acid is ionized and the amine is protonated Correct answer.
  2. The acid is protonated and the amine is neutral
  3. Both groups are predominantly un-ionized
  4. Both groups are predominantly neutral

Explanation

At pH 7.4, above the acid pKa, the carboxylate is deprotonated (ionized). Below the amine pKa, the amine is protonated. The molecule therefore exists as a zwitterion.

Question 24Pharmaceutical Chemistry and Medicinal Chemistry

Which structural feature most distinguishes a selective COX-2 inhibitor from a nonselective NSAID such as ibuprofen?

  1. A nitroimidazole ring
  2. A beta-lactam ring
  3. A quaternary ammonium group
  4. A bulky sulfonamide or sulfone substituent on a diaryl framework Correct answer.

Explanation

Selective COX-2 inhibitors such as celecoxib feature a diaryl scaffold with a bulky sulfonamide or methylsulfonyl group that occupies the side pocket of COX-2. This bulk is poorly accommodated by COX-1.

Question 25Pharmaceutical Chemistry and Medicinal Chemistry

A drug's metabolic clearance is saturable at therapeutic concentrations. Which kinetic consequence is expected as concentration rises?

  1. Half-life becomes independent of dose
  2. Clearance decreases and half-life lengthens Correct answer.
  3. Elimination becomes zero-order at all concentrations
  4. Clearance increases proportionally with concentration

Explanation

When metabolism approaches saturation (Michaelis-Menten), clearance falls as concentration rises and the apparent half-life lengthens. At full saturation elimination becomes zero-order, but not at all concentrations.

Question 26Pharmaceutical Chemistry and Medicinal Chemistry

Which functional group undergoes glucuronidation most readily in Phase II metabolism?

  1. A hydroxyl group Correct answer.
  2. An aromatic ring
  3. A methyl group
  4. A tertiary amine

Explanation

UDP-glucuronosyltransferases conjugate glucuronic acid onto nucleophilic groups, and hydroxyl groups (phenolic or aliphatic) are the classic substrates. The reaction adds a bulky, ionizable sugar moiety that increases water solubility and biliary excretion. Groups lacking a suitable nucleophilic atom are not direct substrates for this pathway.

Question 27Pharmaceutical Chemistry and Medicinal Chemistry

Which physicochemical property best explains why a highly lipophilic drug tends to have a large apparent volume of distribution?

  1. High plasma protein binding
  2. Extensive partitioning into tissue lipids Correct answer.
  3. Low molecular weight
  4. High aqueous solubility

Explanation

A large volume of distribution reflects distribution out of plasma into tissues, which is favored by lipophilicity and membrane permeation. Highly lipophilic compounds accumulate in fat and tissue membranes, lowering plasma concentration relative to dose. Plasma binding and aqueous solubility act in the opposite direction by retaining drug in the vascular space.

Question 28Pharmaceutical Chemistry and Medicinal Chemistry

A medicinal chemist replaces a metabolically labile ester in a lead compound with an amide to improve stability. What is the principal rationale for this modification?

  1. The amide lowers the compound's molecular weight
  2. The amide increases the compound's lipophilicity substantially
  3. The amide introduces a new chiral center
  4. The amide is more resistant to hydrolytic cleavage by esterases Correct answer.

Explanation

Amide bonds are resonance-stabilized and therefore hydrolyze much more slowly than esters under physiological conditions and in the presence of esterases. This reduces metabolic clearance and can prolong half-life. The trade-off is generally increased polarity and hydrogen-bonding capacity rather than increased lipophilicity.

Question 29Pharmaceutical Chemistry and Medicinal Chemistry

A drug is a weak base with a pKa of 8.0. In urine at pH 6.0, which manipulation would most increase its renal elimination?

  1. Decreasing renal blood flow
  2. Alkalinizing the urine Correct answer.
  3. Acidifying the urine further
  4. Increasing plasma protein binding

Explanation

For a weak base, the un-ionized fraction is trapped in acidic urine, but raising urine pH above the drug's pKa increases the ionized fraction. Ionized species are poorly reabsorbed across the tubular membrane, so alkalinizing the urine promotes excretion. This is the basis of ion trapping in overdose management.

Question 30Pharmaceutical Chemistry and Medicinal Chemistry

A lead compound binds its target through a carboxylic acid that forms a salt bridge with a lysine residue. Replacing the carboxylic acid with a tetrazole maintains potency while improving metabolic stability. Which principle best justifies this replacement?

  1. Tetrazole is a prodrug moiety cleaved in vivo
  2. Tetrazole is a bioisostere of the carboxylic acid with a similar pKa Correct answer.
  3. Tetrazole acts as a covalent irreversible inhibitor
  4. Tetrazole eliminates the need for target binding

Explanation

A tetrazole is a classical bioisostere of a carboxylic acid: it is acidic, planar, and can form the same ionic interactions with a basic residue. Its pKa is closer to physiological pH, and it is not subject to the same metabolic conjugation as a carboxylate. The goal is to preserve binding while altering physicochemical and metabolic properties.

Question 31Pharmacognosy and Natural Products

Which plant-derived compound is the standard source of the antimalarial drug artemisinin?

  1. Artemisia annua Correct answer.
  2. Cinchona succirubra
  3. Papaver somniferum
  4. Digitalis purpurea

Explanation

Artemisinin is a sesquiterpene lactone endoperoxide obtained from the aerial parts of Artemisia annua (sweet wormwood). Cinchona yields quinine, a structurally unrelated antimalarial alkaloid.

Question 32Pharmacognosy and Natural Products

The active purgative constituents of senna (Cassia angustifolia) belong to which chemical class?

  1. Sesquiterpene lactones
  2. Cardiac glycosides
  3. Anthraquinone glycosides Correct answer.
  4. Tropane alkaloids

Explanation

Senna contains sennosides, which are dianthrone O-glycosides based on anthraquinone structures that act on the large intestine. Cardiac glycosides, tropane alkaloids, and sesquiterpene lactones have unrelated pharmacological actions.

Question 33Pharmacognosy and Natural Products

Which alkaloid is obtained from the bark of Cinchona species and used to treat nocturnal leg cramps and malaria?

  1. Reserpine
  2. Quinine Correct answer.
  3. Colchicine
  4. Ephedrine

Explanation

Quinine is a quinoline alkaloid from Cinchona bark with antimalarial and skeletal-muscle relaxant uses. Reserpine comes from Rauwolfia, ephedrine from Ephedra, and colchicine from Colchicum.

Question 34Pharmacognosy and Natural Products

Digoxin and digitoxin exert their cardiac effect primarily by which mechanism?

  1. Opening potassium channels
  2. Inhibiting the sodium-potassium ATPase pump Correct answer.
  3. Stimulating adenylate cyclase
  4. Blocking beta-adrenergic receptors

Explanation

Cardiac glycosides inhibit Na+/K+-ATPase, raising intracellular sodium and indirectly increasing intracellular calcium, which strengthens contraction. Beta blockade, potassium channel opening, and adenylate cyclase stimulation describe other drug classes.

Question 35Pharmacognosy and Natural Products

Which natural product is the classic source of the anticancer alkaloids vincristine and vinblastine?

  1. Taxus brevifolia
  2. Podophyllum peltatum
  3. Catharanthus roseus Correct answer.
  4. Colchicum autumnale

Explanation

Vincristine and vinblastine are dimeric indole alkaloids isolated from Catharanthus roseus (Madagascar periwinkle). Podophyllum yields podophyllotoxin, Taxus yields paclitaxel, and Colchicum yields colchicine.

Question 36Pharmacognosy and Natural Products

Tannins are characterized chemically by their ability to do which of the following?

  1. Act as strong oxidizing agents
  2. Form stable salts with chloride ions
  3. Dissolve readily in nonpolar organic solvents
  4. Precipitate proteins and bind to skin collagen Correct answer.

Explanation

Tannins are polyphenolic compounds that complex with and precipitate proteins, which underlies their astringent action on skin and mucous membranes. They are typically water-soluble and are not strong oxidants or chloride-binding salts.

Question 37Pharmacognosy and Natural Products

Which volatile oil constituent is the principal component responsible for the characteristic aroma of peppermint oil?

  1. Menthol Correct answer.
  2. Cinnamaldehyde
  3. Eugenol
  4. Thymol

Explanation

Peppermint oil (Mentha piperita) contains menthol as its major monoterpene alcohol, giving the cooling sensation and characteristic odor. Thymol, eugenol, and cinnamaldehyde are typical of thyme, clove, and cinnamon oils respectively.

Question 38Pharmacognosy and Natural Products

The gum resin asafoetida is obtained from which plant part and genus?

  1. Latex from the fruit of Papaver species
  2. Oleoresin from the rhizome of Ferula species Correct answer.
  3. Resin from the leaf of Cannabis species
  4. Balsam from the bark of Myroxylon species

Explanation

Asafoetida is an oleo-gum-resin obtained by incising the rhizome and root of Ferula species. The other options describe different exudates and plant organs.

Question 39Pharmacognosy and Natural Products

Which alkaloid is the principal active constituent of opium responsible for its analgesic effect?

  1. Thebaine
  2. Codeine
  3. Morphine Correct answer.
  4. Papaverine

Explanation

Morphine is the most abundant and most potent analgesic phenanthrene alkaloid of opium. Codeine is present in smaller amounts and is a weaker analgesic, while papaverine and thebaine lack significant analgesic activity.

Question 40Pharmacognosy and Natural Products

A pharmacist is evaluating a crude drug sample that must contain not less than a specified percentage of an active alkaloid. Which pharmacopeial parameter directly quantifies this requirement?

  1. Assay of active constituents Correct answer.
  2. Loss on drying
  3. Total ash value
  4. Swelling index

Explanation

Assay of active constituents measures the amount of a specified marker compound, such as an alkaloid, and is the parameter used to set minimum content limits. Loss on drying, ash value, and swelling index measure moisture, inorganic residue, and mucilage behavior respectively.

Question 41Pharmacognosy and Natural Products

Which technique is most appropriate for separating and identifying the individual alkaloids in a crude plant extract?

  1. Soxhlet extraction
  2. Karl Fischer titration
  3. Kjeldahl nitrogen determination
  4. Thin-layer chromatography Correct answer.

Explanation

Thin-layer chromatography separates components by differential migration on a stationary phase, allowing individual alkaloids to be resolved and identified by Rf values. The other techniques measure nitrogen, moisture, or perform extraction rather than separation.

Question 42Pharmacognosy and Natural Products

The swelling index of a crude drug is most useful for evaluating which type of drug?

  1. Fixed oil-containing drugs
  2. Mucilage-containing drugs Correct answer.
  3. Alkaloid-containing drugs
  4. Volatile oil-containing drugs

Explanation

The swelling index measures the volume occupied by a drug after swelling in water, which reflects its mucilage content and is used for gums and mucilaginous drugs. Alkaloids, volatile oils, and fixed oils are assessed by other parameters.

Question 43Pharmacognosy and Natural Products

Which plant is the commercial source of the laxative glycoside sennoside used in standardized senna extracts?

  1. Plantago ovata
  2. Aloe vera
  3. Rheum palmatum
  4. Cassia angustifolia Correct answer.

Explanation

Cassia angustifolia (senna) is cultivated specifically for its sennoside content, which is standardized in senna leaf and pod preparations. Aloe and rhubarb contain related anthraquinones but are not the sennoside source, and Plantago provides mucilage.

Question 44Pharmacognosy and Natural Products

Which of the following is a characteristic chemical feature of cardiac glycosides such as digoxin?

  1. A quinoline nucleus with a methoxy group
  2. A purine ring bearing a ribose unit
  3. A beta-lactam ring fused to a thiazolidine
  4. A steroid nucleus linked to a sugar moiety Correct answer.

Explanation

Cardiac glycosides consist of a steroidal aglycone (genin) bearing a lactone ring and attached to one or more sugar residues. Beta-lactam, quinoline, and purine-ribose structures belong to antibiotics, quinine, and nucleosides respectively.

Question 45Pharmacognosy and Natural Products

Reserpine lowers blood pressure through which pharmacologic action?

  1. Blocking angiotensin II receptors
  2. Inhibiting HMG-CoA reductase
  3. Stimulating beta-1 receptors in the heart
  4. Depleting catecholamines from adrenergic nerve terminals Correct answer.

Explanation

Reserpine, an indole alkaloid from Rauwolfia serpentina, inhibits vesicular monoamine storage, depleting norepinephrine from adrenergic terminals and thereby reducing blood pressure. The other mechanisms belong to unrelated antihypertensive drug classes.

Question 46Pharmacognosy and Natural Products

Etoposide is a semisynthetic anticancer agent derived from which natural precursor?

  1. Paclitaxel
  2. Podophyllotoxin Correct answer.
  3. Vincristine
  4. Camptothecin

Explanation

Etoposide is prepared semisynthetically from podophyllotoxin, a lignan obtained from Podophyllum species. Vincristine, camptothecin, and paclitaxel give rise to other anticancer derivatives and are not the precursor for etoposide.

Question 47Pharmacognosy and Natural Products

A crude drug is described as containing a fixed oil with a high iodine value. What does this value indicate?

  1. A high degree of unsaturation in the fatty acids Correct answer.
  2. A high content of free fatty acids
  3. A high proportion of unsaponifiable matter
  4. A high moisture content

Explanation

The iodine value measures the grams of iodine absorbed by 100 g of oil and is a direct index of the number of double bonds, hence the degree of unsaturation. Acid value reflects free fatty acids, while unsaponifiable matter and moisture are measured by separate tests.

Question 48Pharmacognosy and Natural Products

Which statement best explains why fresh plant material is often stabilized before extraction of volatile oils?

  1. Enzymatic hydrolysis can degrade labile oil constituents Correct answer.
  2. Volatile oils are insoluble in all solvents
  3. Drying converts monoterpenes into alkaloids
  4. Fresh tissue contains no volatile oil

Explanation

In fresh tissue, endogenous enzymes can hydrolyze or oxidize volatile constituents, so controlled drying or enzyme inactivation preserves the oil profile. Volatile oils are soluble in organic solvents, fresh tissue does contain them, and monoterpenes are not converted to alkaloids.

Question 49Pharmacognosy and Natural Products

Which plant-derived product is used as a bulk-forming laxative because of its high mucilage content?

  1. Plantago ovata seed husk Correct answer.
  2. Senna pod
  3. Castor oil
  4. Cascara sagrada bark

Explanation

Plantago ovata (psyllium) seed husk is rich in hydrophilic mucilage that absorbs water and increases stool bulk. Senna and cascara act as stimulant anthraquinone laxatives, and castor oil is a lubricant/stimulant oil.

Question 50Pharmacognosy and Natural Products

Which of the following best describes the role of a marker compound in the standardization of a herbal extract?

  1. A compound added to increase the extract's potency
  2. A chemically defined constituent used to quantify or verify the extract Correct answer.
  3. A contaminant used to detect adulteration
  4. A solvent residue measured after extraction

Explanation

A marker compound is a chemically defined constituent, active or not, used to quantify or fingerprint a herbal extract for consistency and quality control. It is not added to boost potency, is not a contaminant, and is distinct from residual solvent testing.