OIA2007 [QUIZLET] GLYCOSIDES

What is a glycoside?

An organic molecule in which a sugar group is bonded through its anomeric carbon to another group via a glycosidic bond.

What forms a glycosidic bond?

A glycosidic bond is formed between the hemiacetal group of a saccharide and the hydroxyl group of an alcohol.

What are the two components of a glycoside?

The sugar group (glycone) and the non-sugar group (aglycone or genin).

What types of sugar groups can be found in glycosides?

The glycone can consist of a monosaccharide or several sugar groups (oligosaccharide). Common sugars include glucose and rhamnose.

How can the glycone and aglycone portions of a glycoside be separated?

They can be chemically separated by acid hydrolysis or enzymatic hydrolysis.

What are the general physicochemical properties of glycosides?

They are crystalline or amorphous, soluble in water or alcohols, insoluble in organic solvents, optically active, and hydrolyzed by water, enzymes, and mineral acids.

What is the significance of the glycosidic bond in glycosides?

It is unstable and susceptible to hydrolysis by dilute acid or enzymes.

What is the most common sugar found in glycosides?

β-D-glucose.

What are some examples of glycosides?

Examples include anthraquinone glycosides like senna, rhubarb, aloe, cascara, and cardiac glycosides like digitalis.

What is the role of polar functional groups in glycosides?

They contribute to the degree of solubility in polar solvents.

What effect does the number of sugar units have on glycoside solubility?

The polar nature and number of sugar units contribute to the solubility in polar solvents.

What is the structure of salicin?

Salicin is an alcoholic β-glucoside with one glucose unit.

What are 6-deoxyhexoses and give examples?

6-deoxyhexoses are sugars like rhamnose and digitalose, commonly found in glycosides.

What are 2,6-dideoxysugars and where are they found?

2,6-dideoxysugars like digitoxose and cymarose are common in cardiac glycosides.

What is the significance of isomers in glycosides?

Determining which isomer has activity is important, as natural glycosides tend to have β linkages.

What is a common branched oligosaccharide found in glycosides?

Digitonin, which has a branched pentasaccharide chain.

What are some examples of sugars that can be glycones in glycosides?

Examples include galactose, ribose, xylose, and arabinose.

What is the role of glucuronic acid in glycosides?

Glucuronic acid is found in glycyrrhizin, a type of glycoside.

What is the relationship between glycosides and solubility in organic solvents?

Glycosides with larger sugar portions are less soluble in organic solvents like ether.

What happens to glycosides during acid hydrolysis?

Acid hydrolysis cleaves α or β-glycosides, releasing the aglycone.

What is the effect of sugar molecules on the solubility of glycosides?

The presence of sugar molecules affects the solubility, with larger sugar portions reducing solubility in alcohol or aqueous solutions.

What is the significance of the aglycone in glycosides?

The aglycone is the organic part of the glycoside and can influence the properties and activity of the glycoside.

What is the chemical reaction that forms a glycosidic bond?

Aglycone-OH + HO-Glycone = Aglycone-O-Glycone + H2O.

What is salicin and where is it produced?

Salicin is an alcoholic β-glucoside produced in willow bark.

What is the solubility characteristic of salicin compared to larger glycosides?

Salicin with one glucose unit is soluble in ether, while glycosides with a larger sugar portion are less soluble in alcohol or aqueous alcoholic solutions.

What is a biosynthetic precursor to salicylaldehyde?

Salicin.

Which plant families contain important glycosides?

1. Scrophulariaceae (e.g., Digitalis purpurea, Digitalis lanata). 2. Liliaceae (e.g., Urginea indica, Aloe vera). 3. Leguminosae (e.g., Cassia acutifolia, Glycyrrhiza glabra). 4. Simarubaceae (e.g., Quassia). 5. Polygonaceae (e.g., Rhubarb). 6. Rhamnaceae (e.g., Cascara sagrada).

How can glycosides be hydrolyzed?

Glycosides can be hydrolyzed by acid hydrolysis, enzymatic hydrolysis, or alkaline cleavage.

What happens during acid hydrolysis of glycosides?

Glycosidic linkages are cleaved by heating with a dilute acid, with different sugars hydrolyzed to varying degrees.

Which sugars are hydrolyzed more easily during acid hydrolysis?

2-Deoxysugars are hydrolyzed easier than 6-deoxy sugars, which are easier than normal sugars.

What is the role of enzymes in glycoside hydrolysis?

Enzymes found in the same plant can hydrolyze glycosides, typically involving β-D-glucose.

Name an enzyme that hydrolyzes glycosides in Digitalis purpurea.

Digitalidase.

What is the effect of alkaline solutions on glycosidic linkages?

Alkali do not cleave glycosidic linkages but can cleave ester groups.

What are O-glycosides?

O-glycosides are formed when a sugar molecule is combined with a phenol or -OH group of an aglycone.

What are N-glycosides?

N-glycosides are formed when a sugar molecule is combined with the nitrogen of an amino group in an aglycone.

What are S-glycosides?

S-glycosides are formed when a sugar molecule is combined with the sulfur or thiol group of an aglycone.

What are C-glycosides?

C-glycosides are formed when a sugar molecule is directly attached to a carbon atom of an aglycone.

What distinguishes β-glycosides from α-glycosides?

β-glycosides involve a sugar with β-configuration, while α-glycosides involve a sugar with α-configuration.

What are some examples of glycosides based on their aglycone moiety?

1. Anthracene glycosides (e.g., Senna). 2. Cardiac glycosides (e.g., Digitalis). 3. Flavonoid glycosides (e.g., Rutin). 4. Saponin glycosides (e.g., Quillaia). 5. Cyanogenic glycosides (e.g., Wild cherry bark). 6. Phenolic glycosides (e.g., Arbutin). 7. Alcohol glycosides (e.g., Salicin). 8. Antibiotic glycosides (e.g., Gentamicin).

What is the significance of the lactone ring in cardiac aglycones?

The lactone ring at C17 can be opened by strong alkalis, leading to a loss of cardiotonic activity, which is reversible upon addition of acid.

What type of glycoside is salicin classified as?

Salicin is classified as an alcoholic glycoside.

What is the relationship between glycosides and their stability?

C-glycosides are more resistant to acid hydrolysis than O-glycosides.

What is the role of β-glycosidases in glycoside hydrolysis?

β-glycosidases can hydrolyze most β-glycosides, allowing for stepwise hydrolysis of monosaccharide units.

What are some examples of glycosides based on their sugar moiety?

1. Glucosides (e.g., Glucose). 2. Ribosides (e.g., Ribose). 3. Rhamnosides (e.g., Rhamnose).

What are ester glycosides?

Glycosides of methyl salicylates, e.g., gualtherin.

What are aldehyde glycosides?

Glycosides with an aldehyde aglycone, e.g., glucovanillin.

What are monoterpene glycosides?

A type of terpene glycoside, examples include gentiopicrin and loganin.

What are triterpene saponin glycosides?

A category of glycosides that includes triterpene saponins.

What defines glycoalkaloids?

They possess a glycosidic linkage and a cyclic nitrogen in the aglycone, e.g., steroidal alkaloids of Solanum species like solanine.

What is the Stas-Otto method for isolation of glycosides?

A method involving continuous hot percolation using alcohol as a solvent to extract glycosides.

What is the purpose of treating the extract with lead acetate during glycoside extraction?

To precipitate tannins and eliminate non-glycosidic impurities.

How is excess lead acetate removed from the extract?

By passing hydrogen sulfide (H2S) gas through the solution, precipitating it as lead sulfide (PbS).

What techniques are used to obtain pure glycosides from crude extracts?

Fractional solubility, fractional crystallization, and chromatographic techniques such as preparative thin-layer and column chromatography.

What methods are used for the characterization of isolated glycosides?

IR, UV, visible, NMR, mass spectrophotometry, and elemental analysis.

What are the conditions for the extraction and isolation of glycosides?

Neutral and alkaline conditions are preferred; no acidic conditions.

What are the steps to inactivate enzymes during glycoside extraction?

Boiling with alcohol or acetone, using low or high temperatures depending on the enzyme type, or precipitating with ammonium sulfate.

What are the recommended conditions for the starting plant material in glycoside extraction?

It should be dried and well stored, with water content kept below 10% to prevent glycoside decomposition.

What are some cold extraction procedures for glycosides?

Room temperature extraction using percolation and maceration with water or alcohol mixtures.

What are anthracene glycosides?

Biologically active purgatives found in several plant drugs, occurring more commonly in glycoside form than aglycone form.

What are the structural features of anthracene glycosides?

Based on the anthracene molecule, with three substituted forms existing naturally.

What are the common anthraquinone aglycone structures found in senna leaves?

Four structures exist, with the glycoside being the biologically active part.

What is the significance of Rhein-O-Glucoside?

It is a monoglucoside at C8 of the anthraquinone molecule.

What is the significance of Rhein-O-Diglucoside?

It is a diglucoside at C1 & C8 of the anthraquinone molecule.

What is Aloin?

A C-glucoside with a direct C-linkage found in anthraquinone compounds.

What color indicates the presence of anthraquinone derivatives in a drug test?

A pink/red color after maceration with ether and treatment with dilute acid followed by ammonia or caustic soda.

Which plants are known to contain anthraquinones used as purgative drugs?

Rhubarb, Senna, Aloes, and Cascara.

What is the botanical source of Alexandrian senna?

The dried leaflets of Cassia acutifolia Delile (C. senna L.) and C. angustifolia Vahl.

Where is Senna widely cultivated?

In Egypt and the middle-upper territories of the Nile River, Sudan, and India.

What are the main sennosides found in Senna?

Sennoside A and sennoside B, which are based on the aglycones sennidin A and sennidin B.

What additional chemical constituents are found in Senna?

Sennosides C and D, palmidin A, rhein anthrone, aloe-emodin glycosides, free chrysophanol, emodin, and their glycosides.

What is the significance of mucilage in Senna leaves?

Mucilage is present in the epidermis of the leaf and gives a red color.

What types of structures exist in the Senna leaf?

Four Anthraquinone aglycone structures.

What is Aloe, and where is it commonly found?

Aloe is the dried juice from various species of Aloe, commonly found in East and South Africa, the West Indies, and Mediterranean countries.

What are the chemical constituents of Aloe?

Aloin, Barbaloin, Aloesin, emodin, and aloe-emodin.

What is the biological source of Rhubarb?

Peeled dried rhizomes and roots of Rheum palmatum Linn., belonging to the family Polygonaceae.

Where is Rhubarb primarily found?

In East Asia, particularly in N.W. China, Yunnan, W. Sichuan, E. Xizang, Gansu, Tibet, and India.

What are the main chemical constituents of Rhubarb?

Free anthraquinones, their glycosides, chrysophanol, aloe-emodin, emodin, physcion, rhein, tannoid constituents, starch, and calcium oxalate.

What is Cascara and what is its source?

Cascara is the dried bark of Rhamnus purshiana DC., belonging to the family Rhamnaceae.

Where is Cascara indigenous to?

North America, British Columbia, Canada, and Kenya.

What are the primary glycosides found in Cascara bark?

Aloin or barbaloin, 11-deoxyaloin or chrysaloin, and cascarosides A, B, C, and D.

What additional components does Cascara contain?

Chrysaloin, barbaloins, dianthrones of emodin, aloe-emodin, chrysophanol, and a bitter lactone.

What is the composition of cardiac glycosides?

They are composed of a sugar (glycone) and a non-sugar (aglycone) moiety.

What is the structure of the aglycone portion of cardiac glycosides?

It is a steroid nucleus with a unique set of fused rings (A, B, C, and D).

What is the configuration of the rings in cardiac steroids?

Rings A-B and C-D are cis fused, while ring B-C has a trans configuration.

What are the typical features of cardiac steroids?

They usually have two angular methyl groups at C10(19) and C13(18), with OH groups at C3 and C14.

What is the significance of the lactone ring in cardiac glycosides?

C17 has the lactone ring, which can be five-membered (cardenolide) or six-membered (bufadienolide).

What variations can occur in the lactone ring of cardiac glycosides?

The size and degree of unsaturation of the lactone ring vary with the source of the glycoside.

What is the aglycone nucleus in cardiac steroids?

The aglycone nucleus is the non-sugar part of cardiac glycosides.

What type of glycosidic link is found in the glycone moiety of cardiac glycosides?

The glycone moiety contains a β-1,4-glycosidic link.

Which sugars are commonly found in cardiac glycosides?

Common sugars include D-glucose, D-digitoxose, L-rhamnose, and D-cymarose.

Where are cardiac glycosides primarily sourced from?

Cardiac glycosides mainly occur in plants.

What is the biological source of Digitalis purpurea?

Digitalis purpurea consists of the dried leaves of the foxglove plant.

List some geographical sources where Digitalis purpurea can be found.

Digitalis purpurea is found in England, Germany, France, North America, India, Iraq, Japan, Kurdistan, Mexico, Nepal, Spain, and Turkey.

What are the glycosides derived from Digitalis purpurea?

Purpurea glycoside A (Digitoxin) and Purpurea glycoside B (gitoxin).

What are the main glycosides derived from Digitalis lanata?

Lanatoside A (Digitoxin), Lanatoside B (gitoxin), and Lanatoside C (Digoxin).

What is the biological source of Digitalis lanata?

Digitalis lanata consists of the dried leaves of the plant.

Where is Digitalis lanata primarily found?

It is mainly found in Central and Southern Europe, England, California, and India.

What is the structure of Purpurea glycoside A?

Purpurea glycoside A is composed of glucose-(digitoxose)3 linked to digitoxigenin.

What is the structure of Purpurea glycoside B?

Purpurea glycoside B is composed of glucose-(digitoxose)3 linked to gitoxigenin.

What distinguishes Lanatoside A from Lanatoside B?

Lanatoside A has an acetyl group on the third digitoxose, while Lanatoside B does not.