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Questions and Answers
Which of the following statements about alkaloids is correct?
Which of the following statements about alkaloids is correct?
- Alkaloids can be characterized by their reaction with specific reagents. (correct)
- Alkaloids typically do not contain nitrogen.
- Caffeine is detected with Mayer’s reagent.
- All compounds containing nitrogen are alkaloids.
What color does Dragendorff’s reagent produce in the presence of alkaloids?
What color does Dragendorff’s reagent produce in the presence of alkaloids?
- Blue
- Green
- Orange (correct)
- Creamy white
Which alkaloid is known to increase peripheral blood supply?
Which alkaloid is known to increase peripheral blood supply?
- Morphine
- Caffeine
- Quinine
- Ephedrine (correct)
What is the primary function of tannins as polyphenolic compounds?
What is the primary function of tannins as polyphenolic compounds?
What distinguishes caffeine from most other alkaloids in a chemical test?
What distinguishes caffeine from most other alkaloids in a chemical test?
What color is observed when testing for condensed tannins using ferric chloride?
What color is observed when testing for condensed tannins using ferric chloride?
Which statement correctly describes the primary pharmacological action of tannins?
Which statement correctly describes the primary pharmacological action of tannins?
What is the predominant characteristic of essential oils?
What is the predominant characteristic of essential oils?
Which components are primarily responsible for the characteristics of essential oils, such as those from Mentha piperita?
Which components are primarily responsible for the characteristics of essential oils, such as those from Mentha piperita?
What is the color change observed when essential oils are tested with Sudan III?
What is the color change observed when essential oils are tested with Sudan III?
What distinguishes primary metabolites from secondary metabolites in plants?
What distinguishes primary metabolites from secondary metabolites in plants?
What is a common characteristic of secondary metabolites?
What is a common characteristic of secondary metabolites?
Which of the following is categorized as a primary metabolite?
Which of the following is categorized as a primary metabolite?
Which statement about alkaloids is correct?
Which statement about alkaloids is correct?
Which of the following metabolites is NOT a primary metabolite?
Which of the following metabolites is NOT a primary metabolite?
What is the role of primary metabolites in plants?
What is the role of primary metabolites in plants?
What is an example of a secondary metabolite?
What is an example of a secondary metabolite?
Which of the following statements about primary metabolites is false?
Which of the following statements about primary metabolites is false?
Which pharmacological action is associated with thyme oil?
Which pharmacological action is associated with thyme oil?
What type of structures secrete volatile oils?
What type of structures secrete volatile oils?
Which of the following oils is classified as an analgesic?
Which of the following oils is classified as an analgesic?
What is the primary metabolite type formed by volatile oils?
What is the primary metabolite type formed by volatile oils?
Which part of glycosides is responsible for pharmacological activity?
Which part of glycosides is responsible for pharmacological activity?
What is a characteristic of flavonoid glycosides?
What is a characteristic of flavonoid glycosides?
Which glycoside subclass can release toxic hydrogen cyanide (HCN)?
Which glycoside subclass can release toxic hydrogen cyanide (HCN)?
What type of glycosides includes cardiac glycosides?
What type of glycosides includes cardiac glycosides?
Which of the following structures is NOT a way through which volatile oils are secreted?
Which of the following structures is NOT a way through which volatile oils are secreted?
What common test is associated with fixed and volatile oils?
What common test is associated with fixed and volatile oils?
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Study Notes
Ergastic Cell Contents
- Non-living substances present within cells
- Found in cytoplasm and vacuoles
- Can be identified through microscopic examination and chemical/physical tests
- Divided into primary and secondary metabolites
Primary Metabolites
- Essential for plant survival
- Involved in growth, development and reproduction
- Include carbohydrates, proteins, and lipids
Secondary Metabolites
- Not essential for plant survival
- Have other functions, such as defense mechanisms
- Include alkaloids, volatile oils, tannins, flavonoids, etc
- Absence of secondary metabolites does not lead to immediate death
Alkaloids
- Compounds of biological origin with a nitrogen atom
- Derived from amino acids
- Often have pharmacological activity
- Names typically end in "-ine" (e.g., caffeine)
- Often have a bitter taste
- Examples include: Morphine, Quinine, Vincamine, and Ephedrine
Chemical Identification of Alkaloids
- Mayer's reagent produces a creamy white precipitate with most alkaloids (except caffeine).
- Dragendorff's reagent produces an orange color.
Tannins
- Polyphenols with the ability to precipitate proteins
- Historically used for leather production by cross-linking proteins
- Two main types: Hydrolyzable tannins and Condensed tannins
Test for Hydrolyzable and Condensed Tannins
- Plant water extract is used.
- Ferric chloride is added.
- Condensed tannins react to form a dark greenish-black color.
- Hydrolyzable tannins react to form a dark bluish-black color.
Pharmacological Actions of Tannins
- Astringent action: Anti-diarrheals and haemostatics
- Chelating action: Antidote in poisoning by heavy metals and alkaloids
- Polyphenolic nature: Antioxidant and anticancer
Volatile Oils
- Also known as essential oils
- Volatile aromatic complex mixtures of relatively low molecular weight compounds (terpenes)
- May contain up to 60 components, but two or three major components generally dominate (20-70%)
- They give red color with Sudan III
- Major components determine biological properties
- Examples include Mentha piperita essential oil (menthol and menthone)
Pharmacological Actions of Volatile Oils
- Antiseptic and antimicrobial: Thyme oil
- Analgesic: Mentha oil, clove oil
- Sedative: Lavander oil
- Spasmolytic: Anise oil
- Fragrance: Lemon peel oil
Secretory Structures
- Volatile oils are secreted from:
- Glandular hairs
- Secretory cavities
- Secretory ducts (vitta)
- Secretory cells
Fixed Oils vs Volatile Oils
- Fixed oils are non-volatile, primary metabolites, and form triglycerides.
- Volatile oils are volatile, secondary metabolites, and form terpenoids.
- Both give a red color with Sudan III
- Fixed oils leave a permanent spot on the paper while volatile oils do not.
Glycosides
- Biomolecules composed of two parts: a sugar part (glycone) and a non-sugar part (aglycone or genin).
- The glycosidic bond links the two parts.
- The aglycone part is responsible for the pharmacological activity.
- Several types of glycosides exist based on the type of aglycone.
Types of Glycosides
- Steroidal glycosides (cardiac glycosides)
- Phenolic glycosides
- Cyanogenic glycosides
- Thio-glycosides
- Saponin glycosides
Important Sub Classes of Glycosides
- Flavonoid glycosides: Act as antioxidants.
- Anthraquinone glycosides: Used as laxatives.
Cyanogenic Glycosides
- Contain a cyanogenic group (-CN)
- Release hydrogen cyanide (HCN) gas upon hydrolysis, which is toxic.
- The aglycone contains a sulfur atom.
- Form a persistent froth when shaken (e.g., licorice).
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