CHM 442 – Natural Product II UNILORIN 2020/2021 Rain Semester Examinations

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COURSE TITLE: Natural Product II

COURSE CODE: CHM 442

DURATION: 2 Hours

Instructions

Attempt any Four (4) questions; Begin each question on a fresh page

Question 1a: List Five classes of terpenoids 2 1⁄2 Marks
Question 1b: State the precursor required for the biosynthesis of each of the classes of terpenoids listed above. 2 1⁄2 Marks
Question 1c: Assign the precursor mentioned above for the biosynthesis of the under listed terpenoids. (i) Myrcene (ii) Humulene (iii) Bisabolene (iv) y-terpene (v) a-terpeneol (vi) a-Phellandrene (vii) Squarlene (viii) Germancredene A 5 Marks (ix) Lanosterol (x) Thymol 5 Marks
Question 1d: Use suitable chemical equations to illustrate the biosynthesis of a terpenoids from the assigned precursor. 2 Marks
Question 1e: mention the class of terpenoids that normally predominate in essential oils. 1⁄2 Mark
Question 1f: List Five methods that can be used to extract essential oils from plant material. 2 1⁄2 Marks
Question 1g: Outline the procedure required for the extraction of the oils using any of the methods listed above. 2 Marks
Question 1h: Suggest an instrumental technique that can be used to establish the terpenoids in essential oils 1⁄2 Marks
Question 1i: State the principle of the techniques suggested in Q1(h) above. 1 Mark Total = 18 1⁄2 Marks
Question 2a: Give names and structures of fatty acids that are precursors required for the biosynthesis of prostaglandins 2 Marks
Question 2b: State the series of prostaglandins obtainable from each of the precursors.
Question 2c: (c) Write the protanoic acid skeleton for each of the series signified above.
Question 2d: (d) State five classes of prostaglandins obtainable from the precursors given in Q2(a) above.
Question 2e: Write the structure of a prostaglandin in each of the classes stated above.
Question 2f: Give names and structures of three prostaglandins that are in use as drugs in obstetrics.
Question 2g: State the application of each of the drugs.
Question 3a: List Four (4) classes of steroidal hormones.
Question 3b: Give names and structures of a compound in each of the classes.
Question 3c: Deduce the hydrocarbon skeleton that serves as basis for the nomenclature of each of the compound in Q3(b) above.
Question 3d: Write the structure of hydrocarbon skeleton deduced in Q3(c) above.
Question 3e: Give name and structure of the hydrocarbon skeleton that is common to the classes of steroidal hormones listed above.
Question 3f: State the significance of each of the steroidal hormones given in Q3(b) above.
Question 3g: Suggest two spectroscopic techniques that can be used to establish the identity of the steroidal hormones given in Q3(b) above.
Question 3h: State the principle of the techniques given in Q3(g) above.
Question 4a: Alkaloids, flavanoids, and Chlorophylls are classes of organic compounds found mostly in plants. (a) State the roles of these class of compounds in plants
Question 4b: Mention two of the utilities of these compounds to man
Question 4c: Give a chemical test that can be used to establish the presence of any two of the class of the compounds in plant extracts.
Question 4e: Outline the procedure that can be used to isolate a suggested example of any of the class of compounds in a given plant sample.
Question 4e: State the usefulness of the compound suggested in Q4(d) above.
Question 5a: Mention and describe different types of alkaloids you know
Question 5b: Give name and structure of the main precursors required for the biosynthesis of the type of alkaloids mentioned in Q5(a) above
Question 5c: Itemize five (5) classification of alkaloids based on the chemical structure
Question 5d: Give an example of any four of the classes mentioned in Q5(e) above
Question 5e: Mention the specific importance of each of the compounds given in Q5(d) above

Answers

Answer 1a:
Five classes of terpenoids:
  1. Monoterpenoids (C10)
  2. Sesquiterpenoids (C15)
  3. Diterpenoids (C20)
  4. Triterpenoids (C30)
  5. Tetraterpenoids (C40)
Answer 1b:
Precursors for biosynthesis:
  1. Monoterpenoids: Geranyl pyrophosphate (GPP)
  2. Sesquiterpenoids: Farnesyl pyrophosphate (FPP)
  3. Diterpenoids: Geranylgeranyl pyrophosphate (GGPP)
  4. Triterpenoids: Squalene (from 2 FPP units)
  5. Tetraterpenoids: Phytoene (from 2 GGPP units)
Answer 1c:
Assign precursors to terpenoids:
  1. Myrcene: GPP
  2. Humulene: FPP
  3. Bisabolene: FPP
  4. γ-Terpinene: GPP
  5. α-Terpineol: GPP
  6. α-Phellandrene: GPP
  7. Squalene: 2 FPP
  8. Germacrene A: FPP
  9. Lanosterol: Squalene
  10. Thymol: GPP
Answer 1d:
(d) Biosynthesis example (Myrcene from GPP): GPP → Myrcene + PPi Equation: GPP (C10) undergoes elimination of pyrophosphate to form the monoterpene Myrcene.
Answer 1e:
(e) Class predominant in essential oils: Monoterpenoids and sesquiterpenoids.
Answer 1f:
(f) Extraction methods:
  1. Steam distillation
  2. Solvent extraction
  3. Cold pressing (expression)
  4. Supercritical CO₂ extraction
  5. Enfleurage
Answer 1g:
(g) Procedure for steam distillation:
  1. Heat plant material with water to release volatile oils.
  2. Collect vapor, condense into a mixture of oil and water.
  3. Separate oil via decantation or centrifugation.
Answer 1h:
(h) Instrumental technique: Gas Chromatography-Mass Spectrometry (GC-MS).
Answer 1i:
(i) Principle of GC-MS: GC separates compounds based on volatility and column interaction; MS identifies them via mass-to-charge ratio.
Answer 2a:
Question 2: Prostaglandins (a) Precursors:
  1. Arachidonic acid (C20:4 ω-6): Structure: 20 carbons, 4 double bonds at positions 5,8,11,14.
  2. Dihomo-γ-linolenic acid (DGLA) (C20:3 ω-6): Structure: 20 carbons, 3 double bonds at positions 8,11,14.
Answer 2b:
(b) Prostaglandin series:
  1. Arachidonic acid → Series 2 (e.g., PGE₂)
  2. DGLA → Series 1 (e.g., PGE₁)
Answer 2c:
(c) Prostanoid acid skeleton: Cyclopentane ring with two side chains (carboxylic acid at C1, hydroxyl at C11).
Answer 2d:
(d) Classes of prostaglandins:
  1. PGE (keto group at C9)
  2. PGF (hydroxyl groups at C9 and C11)
  3. PGD (keto group at C9, hydroxyl at C11)
  4. PGA (cyclopentenone ring)
  5. PGB (conjugated diene in ring)
Answer 2e:
(e) Example structures:
  • PGE₂: Cyclopentane with keto (C9) and hydroxyl (C11).
  • PGF₂α: Two hydroxyl groups (C9 and C11).
Answer 2f:
(f) Prostaglandins in obstetrics:
  1. Dinoprostone (PGE₂): Induces labor.
  2. Carboprost (15-methyl PGF₂α): Treats postpartum hemorrhage.
  3. Misoprostol (PGE₁ analog): Cervical ripening.
Answer 2g:
(g) Applications:
  • Dinoprostone: Labor induction.
  • Carboprost: Controls bleeding.
  • Misoprostol: Medical abortion.
Answer 3a:
(a) Classes Steroidal Hormones:
  1. Glucocorticoids
  2. Mineralocorticoids
  3. Androgens
  4. Estrogens
  5. Progestogens
Answer 3b:
(b) Examples Steroidal Hormones:
  1. Cortisol (glucocorticoid): 17-hydroxy, 11β-hydroxy, 3-keto.
  2. Aldosterone (mineralocorticoid): 11β,21-dihydroxy, 18-aldehyde.
  3. Testosterone (androgen): 17β-hydroxy, 4-en-3-one.
  4. Estradiol (estrogen): Aromatic A-ring, 17β-hydroxy.
  5. Progesterone (progestogen): 4-en-3,20-dione.
Answer 3c:
(c) Hydrocarbon skeleton: Cyclopentanoperhydrophenanthrene (four fused rings: 3 cyclohexane, 1 cyclopentane).
Answer 3d:
(d) Structure:
Copy
   D  
C / \ B  
 \   /  
  A

(A, B, C = cyclohexane; D = cyclopentane)

Answer 3e:
(e) Common skeleton: Gonane (steroid nucleus).
Answer 3f:
(f) Significance:
  • Cortisol: Anti-inflammatory, metabolism regulation.
  • Aldosterone: Sodium retention.
  • Testosterone: Male secondary sex characteristics.
  • Estradiol: Female reproductive function.
  • Progesterone: Prepares uterus for pregnancy.
Answer 3g:
(g) Spectroscopic techniques:
  1. Nuclear Magnetic Resonance (NMR)
  2. Infrared (IR) Spectroscopy
Answer 3h:
(h) Principles:
  • NMR: Detects nuclear spin transitions in a magnetic field.
  • IR: Measures vibrational energy transitions in bonds.
Answer 4a:
Question 4: Alkaloids, Flavonoids, Chlorophyll (a) Roles in plants:
  • Alkaloids: Defense against herbivores.
  • Flavonoids: UV protection, pigmentation.
  • Chlorophyll: Light absorption for photosynthesis.
Answer 4b:
(b) Utilities to humans:
  1. Alkaloids: Medicinal drugs (e.g., morphine).
  2. Flavonoids: Antioxidants in diet.
Answer 4c:
(c) Chemical tests:
  1. Alkaloids: Dragendorff’s reagent → orange precipitate.
  2. Flavonoids: Shinoda test (Mg + HCl → red color).
Answer 4e:
(d) Isolation procedure (Alkaloids):
  1. Grind plant material.
  2. Acidify with dilute HCl to extract alkaloids.
  3. Filter and basify with NH₃.
  4. Extract with chloroform.
  5. Evaporate to isolate alkaloids.
Answer 4e:
(e) Usefulness: Example: Quinine (antimalarial).
Answer 5a:
(a) Types:
  1. True alkaloids (heterocyclic N, e.g., morphine).
  2. Protoalkaloids (non-heterocyclic N, e.g., ephedrine).
  3. Pseudoalkaloids (derived from terpenes/purines, e.g., caffeine).
Answer 5b:
Question 5: Alkaloids (b) Precursors:
  1. True: Tryptophan (indole alkaloids).
  2. Proto: Phenylalanine (ephedrine).
  3. Pseudo: Xanthosine (caffeine).
Answer 5c:
(c) Classification by structure:
  1. Indole (e.g., vinblastine)
  2. Isoquinoline (e.g., morphine)
  3. Tropane (e.g., atropine)
  4. Pyrrolidine (e.g., nicotine)
  5. Quinoline (e.g., quinine)
Answer 5d:
(d) Examples:
  1. Indole: Vinblastine (anticancer).
  2. Isoquinoline: Morphine (analgesic).
  3. Tropane: Atropine (pupil dilation).
  4. Quinoline: Quinine (antimalarial).
Answer 5e:
(e) Importance:
  • Vinblastine: Treats lymphoma.
  • Morphine: Pain relief.
  • Atropine: Antidote for nerve agents.
  • Quinine: Malaria treatment.

Note: Structures are implied here; in the exam, draw chemical structures where required.

 

 

CHM 442 – Natural Product II UNILORIN 20202021 Rain Semester Examinations-1

 

CHM 442 - Natural Product II UNILORIN 20202021 Rain Semester Examinations-2
CHM 442 – Natural Product II UNILORIN 20202021 Rain Semester Examinations-2

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