Pharmacognosy Chapter 5

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Questions and Answers

Which type of glycoside is formed through a condensation reaction involving oxygen?

Sulphur glycosides

Cyanophore glycosides

Carbon glycosides

Ether linkage glycosides (correct)

What process leads to the formation of cyanophore glycosides?

Hydrolysis of sugar

Addition of carbon

Loss of nitrogen

Loss of water (correct)

Which of the following is NOT a type of glycoside mentioned?

Cyanophore glycosides

Nitrogen glycosides (correct)

Carbon glycosides

Ether glycosides

What is the key characteristic of sulphur glycosides?

They contain a thio (sulphur) linkage Signup and view all the answers

In the context of glycosides, what does the 'C-' suffix indicate?

Carbon glycosides Signup and view all the answers

What effect do cardiac glycosides have on renal circulation?

They increase renal circulation. Signup and view all the answers

Which is an example of a cardiac glycoside mentioned?

Digitoxose Signup and view all the answers

Which of the following is not a characteristic of cardiac glycosides?

They are primarily used for gastrointestinal issues. Signup and view all the answers

What method is used for the identification of cardiac glycosides?

Chemical tests Signup and view all the answers

Which statement about diuretic effects of cardiac glycosides is correct?

They cause both renal circulation increase and diuretic effects. Signup and view all the answers

What are anthocyanin glycosides primarily known for?

Their contribution to the coloration of flower petals Signup and view all the answers

Which group of compounds are anthocyanin glycosides structurally related to?

Flavonoids Signup and view all the answers

Which glycoside is derived from Black Mustard seeds?

Sinigrin Signup and view all the answers

Which of the following is NOT a characteristic of anthocyanin glycosides?

They are responsible for the smell of flowers Signup and view all the answers

What type of gas is associated with Sinigrin from Black Mustard seeds?

Mustard irritant gas Signup and view all the answers

What role do anthocyanin glycosides play in plants?

They act as attractants for pollinators Signup and view all the answers

Which of the following is a characteristic of Sinalbin derived from white Mustard seeds?

Non-volatile compound Signup and view all the answers

Which statement is true about the color of anthocyanin glycosides?

They provide red, blue, or purple coloration Signup and view all the answers

What is the chemical structure notation for thioglycosides?

S-C=N Signup and view all the answers

Which of these compounds is associated specifically with sulpher glycosides?

Sinalbin Signup and view all the answers

What color precipitate does Mayer's reagent produce with most alkaloids?

Creamy White Signup and view all the answers

Which alkaloid does not produce a precipitate when treated with Mayer's reagent?

Caffeine Signup and view all the answers

What is the color produced by Dragendorff's reagent when it reacts with alkaloids?

Orange Signup and view all the answers

Which reagent is commonly used to identify alkaloids aside from Mayer's reagent?

Dragendorff's reagent Signup and view all the answers

What effect do drugs containing saponins generally have on the mucous membranes?

They are sternutatory and irritating. Signup and view all the answers

Mayer's reagent is primarily used to test for which class of compounds?

Alkaloids Signup and view all the answers

Which of the following uses is NOT associated with saponins?

As a dietary supplement Signup and view all the answers

What property of saponins makes them effective in cleaning applications?

Their ability to emulsify Signup and view all the answers

Which part of the body is primarily affected by the sternutatory nature of saponins?

The respiratory system Signup and view all the answers

In addition to cleaning, what is another major application of saponins?

As an emulsifier for certain resins Signup and view all the answers

False Signup and view all the answers

Study Notes

Lecture 5: Pharmacognosy I (PHCG 111)

Secondary Plant Metabolites (Active Constituents)
- Secondary metabolites act as protective agents, waste products of metabolism, and aid in producer survival.
- They are energy producers and physiologically active.
- These metabolites are various organic compounds.

Compounds composed of carbon, hydrogen, and oxygen as polyhydroxy aldehydes or ketone alcohols, such as sucrose, lactose, starch, gums, mucilage, and pectin.
Gums
- Polysaccharides or salts of Polysaccharides.
- Produced in higher plants as protective agents after injury.
- On hydrolysis, gums yield arabinose, galactose, glucose, mannose, and various uronic acids (which can form salts with Ca, Mg, and other cations).
- Examples: gum acacia and gum tragacanth.

Mucilage

Polysaccharide complexes.
Insoluble in alcohol, forming viscous, non-adhesive colloidal solutions in water, which do not form jelly.
Types include:
- Pectose type (red color with ruthenium red, eg. Senna, Buchu, and Henna leaves)
- Callose type (red color with corallin soda, eg. squill)
- Neutral type (blue color with methylene blue, eg. Foenugreek)

Pectin

Purified carbohydrate (CHO) extracted from dilute acid extracts of the inner rind of citrus fruits or apple pomace.
Soluble in 20 parts water, forming a stiff gel.
Used as a protective and suspending agent, and an ingredient in antidiarrheal preparations.

Glycosides

Non-reducing organic compounds that yield one or more sugars upon hydrolysis using dilute acids, alkalis, or enzymes.
The non-sugar part is called the aglycone (genin), and the sugar component is the glycone.
Chemically, glycosides are considered sugar ethers, formed by water loss and linkage formation (O-, C-, S-, CN-).
Glycosides are generally soluble in water and hydro-alcoholic solvents due to the hydrophilic nature of the sugar. The higher the sugar content, the lower the solubility in organic solvents. The aglycone is more soluble in organic solvent.

Types of Glycosides

A. Phenolic Glycosides
- i. Simple Phenolic Glycosides: e.g., Arbutin (a hydroquinone glycoside) from Uva ursi leaves, used in urethritis and cystitis.
- ii. Flavonoid Glycosides: Largest group of naturally occurring phenols occurring in plants as free aglycones, or as glycosides. Examples: Diosmin (Buchu), Hesperidin (Citrus species). They are yellow compounds, dissolving in aqueous alkali and giving a canary-yellow color.
- iii. Anthocyanin Glycosides: Structurally related to flavonoids, producing pigment in colored flower petals. Their color changes (red-violet to blue) are pH-dependent (e.g., Karkadeh).
- iv. Anthraquinones Glycosides: Pharmacologically active constituents in laxatives and purgatives (e.g., Senna). Give positive Borntrager's and modified Borntrager's tests.
B. Alcoholic Glycosides (Cardiac Glycosides):
- Exert powerful action on cardiac muscles.
- Small amounts can stimulate a diseased heart, but large doses cause death.
- Used to increase cardiac muscle tone, excitability, and contractility, and as diuretics due to increased renal circulation.
- Example: Digitalis.
- SAR (Structure-Activity Relationship) for Cardiac Glycosides: Steroidal nucleus and lactone ring (5- or 6-membered) with a deoxy sugar (e.g. Digitoxose). Detection of cardiac glycosides: chemical tests for steroidal nucleus and deoxy sugars and unique lactone rings.
ii. Saponin Glycosides:
- Characterized by foaming in water, causing red blood cell lysis (hemolysis), sternutatory effects, and irritation of mucous membranes (eyes/nose).
- Used as emulsifiers in industrial cleaning and for certain resins, fats, and fixed oils.
C. Cyanophore Glycosides:
- Yield HCN upon hydrolysis.
- Limited use in pharmacy due to HCN's toxicity.
- Detected by reaction with sodium picrate paper (Grignard Reaction).
D. Thioglycosides:
- Contain thiocyanate (S-C≡N) or sulphur.
- Examples: Sinigrin (from black mustard seeds, mustard irritant gas) and Sinalbin (from white mustard seeds, non-volatile).

Tannins

Large group of complex substances, non-crystalline, with a sharp astringent taste.
- Form colloidal solutions in water.
- Precipitate proteins and alkaloids.
Uses: Astringents, hemostatics, protective coating for burns, antidotes for metal and alkaloid poisoning, tanning of leather, and ink production.
Types:
- Hydrolysable Tannins: Hydrolyzed by acids or enzymes (e.g., tannase), composed of phenolic acids (gallic acid), giving a blue-black color with FeCl3 and no precipitate with bromine water. Examples: clove and galls.
- Condensed Tannins: Not readily hydrolyzed, do not contain sugar moieties, yield catechins on hydrolysis, green color with FeCl3, and precipitate with bromine water. Examples: tea and henna leaves.

Alkaloids

Basic nitrogenous compounds of biological origin.
Physiologically active.
Not all nitrogen-containing compounds are alkaloids.
Generally, alkaloidal bases are insoluble in water but soluble in organic solvents. Alkaloidal salts are soluble in water or sparingly soluble in organic solvents.
Detection:
- Alkaloidal precipitants – e.g. Mayer's reagent (potassium mercuric iodide solution) giving a creamy white precipitate with most alkaloids, except for caffeine.
- Alkaloidal color reagents – e.g. Dragendorff's reagent gives an orange color.

5-Oils

Volatile Oils (Essential Oils):
- Mix of hydrocarbons (mostly terpenes) and oxygenated compounds (e.g., buchu leaves, lavender flowers)
- Volatile, steam-distilled.
- Used as flavoring, in perfumery, and as spices, antiseptics, and carminatives.
- Do not leave a permanent stain on filter paper
- On standing, they become more resinous.
Fixed Oils:
- Triglycerides of fatty acids (e.g., linseed seed).
- Nonvolatile.
- Saponifiable
- Leaves a permanent stain on filter paper
- On standing, they become rancid.
- Used in food and paint industries.

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This quiz covers key concepts from Lecture 5 on Pharmacognosy, including secondary plant metabolites and their functions, carbohydrates and their types, and the role of gums and mucilage in plants. Test your knowledge on plant compounds and their significance in pharmacognosy.