Glycosides and Their Biosynthesis
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Questions and Answers

What do glycosides yield upon hydrolysis?

  • One or more sugars (correct)
  • Only bitter substances
  • Only non-sugar components
  • Saturated solutions

What is the chemical structure of glycosides primarily characterized by?

  • Esters of fatty acids
  • Cetals formed from sugar and non-sugar components (correct)
  • Simple carbohydrates
  • A single sugar component

Which of the following characteristics is NOT typical of glycosides?

  • Soluble in water and diluted alcohol
  • Intensely sweet flavor (correct)
  • Crystalline or amorphous form
  • Usually colorless

Which of the following sources is NOT typically associated with glycosides?

<p>Synthetic chemicals (A)</p> Signup and view all the answers

What is the role of glycosides in pharmacognosy?

<p>They are important for pharmaceuticals and medicinal uses (C)</p> Signup and view all the answers

Which of the following flavonoids is commonly associated with the treatment of capillary bleeding?

<p>Rutin (C), Hesperidin (D)</p> Signup and view all the answers

What type of glycosides are hydrolyzed by emulsin?

<p>Alcohol glycosides (A)</p> Signup and view all the answers

Which compound is the aglycone for vanilla?

<p>Methylprotocatechuic acid (B)</p> Signup and view all the answers

Which of the following sources is NOT associated with vanillin?

<p>Citrus fruits (A)</p> Signup and view all the answers

Which commercial variety of vanillin is known as Bourbon vanilla?

<p>Bourbon vanilla (D)</p> Signup and view all the answers

What is a consequence of potassium depletion in patients taking cardiac glycosides?

<p>Increased risk of cardiac glycosides toxicity (A)</p> Signup and view all the answers

Which of the following contains the active compound digitoxin?

<p>Digitalis purpurea (B)</p> Signup and view all the answers

What effect can parenteral calcium have on patients taking cardiac glycosides?

<p>It can potentiate the cardiac effect (D)</p> Signup and view all the answers

What process likely occurs after the formation of the anthraquinone nucleus in anthraquinone glycoside biosynthesis?

<p>Transglycosylation to form a glycoside (B)</p> Signup and view all the answers

Which of the following is true regarding anthraquinone glycosides and their detection?

<p>They are identified using Borntrager T.S. which shows a reddish color (B)</p> Signup and view all the answers

Which drug is associated with the anticoagulant dicumarol?

<p>Coumarin (A)</p> Signup and view all the answers

What effect does methoxsalen have on patients with idiopathic vitiligo?

<p>Facilitates repigmentation (D)</p> Signup and view all the answers

Which of the following drugs has been discontinued in the US due to potential toxicity?

<p>Santonin (C)</p> Signup and view all the answers

What is the main action of allicin found in garlic?

<p>Antimicrobial (C)</p> Signup and view all the answers

What type of compounds are psoralens classified as?

<p>Furocoumarins (B)</p> Signup and view all the answers

What reaction occurs when arbutin is hydrolyzed?

<p>Arbutin yields hydroquinone and glucose (C)</p> Signup and view all the answers

What caution should be taken when using methoxsalen for repigmentation therapy?

<p>Limit exposure to ultraviolet radiation (A)</p> Signup and view all the answers

Which drug contains the active compound cantharidin?

<p>Cantharides (D)</p> Signup and view all the answers

What is the primary end product formed from the breakdown of prunasin?

<p>Benzaldehyde (C)</p> Signup and view all the answers

Which test is used to identify cyanogenic glycosides?

<p>Guignard Test (C)</p> Signup and view all the answers

What is a common use of the wild cherry (Prunus virginiana)?

<p>Flavored vehicle in cough remedies (D)</p> Signup and view all the answers

What compounds are primarily found in black mustard (Sinapis nigra)?

<p>Sinigrin and allyl isothiocyanate (D)</p> Signup and view all the answers

Which group do glucosinolates belong to?

<p>Isothiocyanate glycosides (C)</p> Signup and view all the answers

What is a property of allyl isothiocyanate from the hydrolysis of sinigrin?

<p>Local irritant and emetic (C)</p> Signup and view all the answers

Which of the following vegetables is known to contain glucosinolates?

<p>Cabbage (C)</p> Signup and view all the answers

What is the effect of indole 3-carbinol derived from the mustard family vegetables?

<p>Reduces the risk of estradiol linked mammary cancer (D)</p> Signup and view all the answers

What are the two main components of glycosides?

<p>Glycone and aglycone (A)</p> Signup and view all the answers

Which enzyme is obtained from almond kernels and is responsible for hydrolyzing glycosides?

<p>Emulsin (D)</p> Signup and view all the answers

What physiological activities are examples of cellular functions associated with glycosides?

<p>Osmosis and diffusion (B)</p> Signup and view all the answers

Which test would be used to identify the presence of cardiac glycosides?

<p>Keller-Killiani test (B)</p> Signup and view all the answers

Which two enzymes hasten the biosynthesis of glycosides?

<p>Uridyl transferase and glycosyl transferase (C)</p> Signup and view all the answers

What is the chemical structure classification of cardenolides?

<p>C23 steroid with a 5-member lactone ring (D)</p> Signup and view all the answers

Which physiological mechanism is involved in the action of cardiac glycosides?

<p>Transport of sodium out and potassium into the cell (C)</p> Signup and view all the answers

Which group does isothiocyanate belong to in glycoside classification?

<p>Other organosulfur drugs (D)</p> Signup and view all the answers

Flashcards

What is a glycoside?

A molecule that breaks down into one or more sugars and a non-sugar component.

What's the aglycone?

The non-sugar part of a glycoside that gives it its unique properties.

What is the glycone?

A sugar molecule attached to the aglycone in a glycoside.

What is glycoside biosynthesis?

The process of forming a glycoside from sugar and a non-sugar molecule.

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What is a glycosidic linkage?

A type of chemical bond that joins the sugar (glycone) to the non-sugar part (aglycone) in a glycoside.

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Glycone

The sugar portion of a glycoside, typically β-D-glucose.

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Aglycone

The non-sugar portion of a glycoside, often a methyl group.

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Endogenous Hydrolysis

Glycosides break down by enzymes present in the same plant tissue where the glycoside is present.

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Exogenous Hydrolysis

Glycosides break down by external agents like mineral acids.

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Emulsin

The enzyme obtained from almond kernels that breaks down glycosides.

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Myrosin

The enzyme obtained from mustard seeds that breaks down glycosides.

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Biosynthesis of Glycosides

Glycoside synthesis involves a sugar residue combining with an aglycone.

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Glycosyl transferases

Enzymes that help transfer a sugar group from uridine diphosphate to an acceptor molecule, forming a glycoside.

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Flavonol Glycosides

Flavonol glycosides are a type of flavonoid with sugar molecules attached. They are known for their antioxidant and anti-inflammatory properties, often found in fruits and vegetables.

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Salicin

Salicin is a natural compound that breaks down into glucose and saligenin, which has pain-relieving effects similar to aspirin.

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Coniferin

Coniferin is a compound found in pine trees and can be converted into vanillin, the primary flavor component of vanilla.

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Amydalin

Amydalin is a naturally occurring compound found in almonds and other fruits, it produces benzaldehyde upon hydrolysis.

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Vanilla

Vanilla is a spice extracted from the seed pods of the vanilla orchid. It is used for its distinctive flavor and aroma and can be obtained from different sources like coniferin, eugenol, and lignin.

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Cardiac Glycosides: Toxicity Factors

Cardiac glycosides are a class of drugs derived from plants that can have toxic effects on the heart. They can be used to treat heart conditions but require careful monitoring. Depleting potassium levels can worsen their toxicity, so patients on diuretics or corticosteroids may need potassium supplementation. Calcium increases cardiac effects so it should not be given.

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Digitalis Purpurea

Digitalis purpurea (Scrophulariaceae), also known as Foxglove, is a plant containing cardiac glycosides, like digitoxin and digoxin, used in heart treatments.

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Borntrager Test

Borntrager test, using Borntrager reagent (concentrated sulfuric acid), is used to detect anthraquinone glycosides by producing a red, orange, or pink color if positive.

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Anthraquinone Glycosides

Anthraquinone glycosides are compounds with a basic structure derived from anthracene. They are naturally occurring in plants and used in various medicinal applications.

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Biosynthesis of Anthraquinone Glycosides

The biosynthesis of anthraquinone glycosides involves several steps, starting with acetate units that condense to form poly-ß-ketomethylene acids. These acids then transform into various aromatic compounds, including anthraquinones and anthranols. The glycoside formation, attaching sugars to the molecule, occurs late in the process.

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Lactone Glycosides

A class of natural compounds that are composed of a lactone ring, which is a cyclic ester, linked to a sugar molecule.

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Dicumarol

A specific type of lactone glycoside known for its anticoagulant properties. It is derived from Anthoxanthum odoratum.

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Cantharidin

A compound found in Cantharis vesicatoria, a type of beetle, that is used for its irritant and blistering properties.

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Psoralens

A group of furocoumarins that cause photosensitivity when exposed to ultraviolet light. They are found in plants like Ammi majus.

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Methoxalen

Also known as 8-methoxypsoralen, Methoxalen is a psoralen used for repigmentation in vitiligo and psoriasis. It requires careful exposure to UV radiation.

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Arbutin

A phenol glycoside found in Arctostaphylos uva-ursi (bearberry) that acts as a diuretic and astringent. It hydrolyzes to hydroquinone and glucose.

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Alliin

An odorless sulfur-containing amino acid derivative found in garlic. It is converted to allicin when cells are crushed.

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Prunasin

A cyanogenic glycoside found in wild cherry bark. It is hydrolyzed to release benzaldehyde, hydrogen cyanide, and glucose.

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Guignard Test

A chemical test used to detect the presence of cyanogenic glycosides. Positive results are indicated by a color change from yellow to maroon.

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Cyanogenic Glycoside

A compound that contains a glucose molecule linked to a cyanide-containing group. These compounds are found in plants and can release hydrogen cyanide when broken down.

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Glucosinolates

A group of sulfur-containing compounds found in plants, especially those from the mustard family. They are known for their strong flavors and potential anticancer properties.

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Sinigrin

A glucosinolate found in black mustard seeds. It is hydrolyzed to release allyl isothiocyanate, glucose, and sulfuric acid.

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Sinalbin

A glucosinolate found in white mustard seeds. It is hydrolyzed to release acrinyl isothiocyanate, glucose, and sulfuric acid.

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Study Notes

Glycosides

  • Glycosides are components that, upon hydrolysis, yield one or more sugars
  • Chemically, they are cetals where a sugar's hydroxyl group bonds with a non-sugar component's hydroxyl group, creating an oxide ring.
  • Physcially, they are often crystalline or amorphous, typically colorless and bitter, dissolving readily in water and diluted alcohol.
  • Glycosides consist of a glycoside (sugar portion) and an aglycone (non-sugar portion)
  • Glycosides can be hydrolyzed by mineral acids or enzymes.

Biosynthesis of Glycosides

  • Glycosides are synthesized through the action of uridyl transferases and glycosyl transferases.
  • Uridyl transferases transfer a uridyl group from uridine triphosphate to a sugar, forming a uridyl sugar.
  • Glycosyl transferases transfer the sugar from uridine diphosphate to an acceptor molecule, forming a glycoside.

Classification of Glycosides

  • Glycosides are classified into groups based on their specific components and activities: cardioactive, anthraquinone, saponin, cyanophore, isothiocyanate, flavonol, alcohol, aldehyde, lactone, phenol groups and others.
  • Some examples of specific glycosides include digitoxin, digoxin, emodin, anthraquinone compounds, cardioactive glycosides, sennosides, and others.

Steroid Glycosides

  • Steroid aglycones are characterized by a cyclopentanoperhydrophenanthrene nucleus.
  • Cardenolides (C23 steroids) have a 5-member lactone ring.
  • Bufadienelides (C24 steroids) have a 6-member lactone ring.
  • Tests for identifying cardiac glycosides include the Keller-Killiani test.

Anthraquinone Glycosides

  • Anthraquinone glycosides are anthracene derivatives, and their detection is done using Borntrager test.
  • Cascara sagrada and Frangula are examples of drugs containing anthraquinone glycosides.

Saponin Glycosides

  • Saponin glycosides are compounds that form colloidal solutions in water, are bitter, and act as hemolytic agents.
  • They're classified as neutral or acid-forming, and contain steroid or triterpenoid sugar portions and sapogenins.
  • The saponin glycosides are vital for their biosynthesis, with acetate and mevalonate units coupling to form different glycosides.

Cyanophore Glycosides

  • These glycosides release hydrocyanic acid upon hydrolysis, and are commonly found in Rosaceae plants.
  • Amygdalin and prunasin are examples, both yielding D-mandelonitrile as the aglycone.
  • Reactions yielding benzaldehyde and hydrocyanic acid occur during the hydrolysis of amygdalin.
  • Guignard test is used for detecting cyanogenic glycosides.

Isothiocyanate Glycosides

  • Found in the mustard family and are pungent and odorless, containing allyl isothiocyanate and benzyl isothiocyanate.
  • Myrosin converts the glucosinolates to the pungent isothiocyanate compounds.
  • White and black mustard are examples of plants containing isothiocyanate glycosides.

Flavonol Glycosides

  • Flavonol glycosides, or flavonoids, frequently contain rutin, quercitrin, hesperidin, hesperetin, diosmin, and others.
  • They're considered vitamin P or permeability factors, involved in capillary bleeding and fragility.

Alcohol Glycosides

  • Alcohol glycosides include salicin, populin, and coniferin.
  • Mineral acids and enzymes may hydrolyze them.

Aldehyde Glycosides

  • Aldehyde glycosides include vanillin, and the aglycones can be aldehydes.

Lacione Glycosides

  • Lacione glycosides include a group of coumarin molecules which is used as an anticoagulant.
  • Cantharides (Spanish flies) are an example, along with anthoxanthum odoratum

Phenol Glycosides

  • Examples include uva ursi, containing arbutin, corilagin, pyroside, quercitin, and more.
  • Arbutin, upon hydrolysis, yields hydroquinone and glucose.

Other Organosulfur Drugs

  • Garlic contains alliin, which, when cells are crushed, converts into allicin through the alliinase enzyme.
  • Allicin has potent antibacterial properties and is responsible for garlic's distinctive odor.

Check for Understanding (Sample Questions)

  • Questions from the provided document are summarized below. The provided text contains a series of questions on various aspects of glycosides. These questions evaluate understanding of specific glycosides, their properties, and related concepts.

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PHA 010: Pharmacognosy and Plant Chemistry Module 5 Student Activity Sheet PDF

Description

Explore the fascinating world of glycosides, which are crucial components yielding sugars upon hydrolysis. This quiz covers their chemical structure, physical properties, biosynthesis, and classification. Test your knowledge on how they are formed and classified within biological systems!

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