PCOG: Glycosides

Glycosides

• Are widely distributed in plant, especially in roots, barks, and fruits

• Chemically, are acetals in which the hydroxyl of glycone is condensed with the hydroxyl group of the aglycones. The secondary hydroxyl is condensed within the sugar molecule itself to from an oxide ring

• Glycosides may be considered as sugar ethers. Only the beta varieties of glycosides exists in plants

General Properties of Glycosides

• All natural glycosides are hydrolyzed into a sugar and another organic compound, by boiling with mineral acids

• Glycosides are easily hydrolyzed by an enzyme that occurs in the same plant tissue, but in different cells from those that contain glycosides. Many of these enzymes hydrolyze only a single glycosides.

• Exception:

  • Enzyme Emulsin from almond kernels and Enzyme Myrosin from black mustards seeds, each hydrolyze a considerable number of glycosides

Cardiac Glycosides

• Have the cyclopenteno-phenanthrene nucleus

• Unsaturated lactone ring at C-17

• B-Hydroxyl at C-14

• Fusion of C and D Rings at C-13 and C-14

• One or more 2-deoxysugars at C-13

Cardiac Glycosides | Keller Killiani Test

Blue or purple coloration indicates the presence of deoxysugars

Cardiac Glycosides | Liebermann-Burchard Test

Changes of the color to blue, green, yellow or purple indicates the presence of steroidal component

Cardiac Glycosides | Kedde Test

Purple coloration indicate the presence of lactone component

Cardiac Glycosides | Strophanthus

• Common Name: Strophanthus or Climbing Oleander

• Scientifc Name: Strophanthus gratus

• Family Name: Apocynaceae

• Constituents: Ouabain or G-Strophanthin

• Use: Cardiotonic

Cardiac Glycosides | Squill Bulb

• Common Name: Squill bulb

• Scientific Name: Urginea maritima

• Family Name: Liliaceae

• Constituents: Scillipicrin and Scillitoxin (Amorphous glycosides), Scillin (Inactive glycosides)

• Uses: Expectorant, Emetic, Cardiotonic and Diuretic

Cardiac Glycosides | Lily of the Valley

• Common Name: Lily of the Valley

• Scientific Name: Convallaria majalis

• Family Name: Liliaceae

• Constituents: Convallarin, Convallamarin & Convallatoxin

• Uses: Diuretic, Similar to the action of digitalis but has no cumulative action

Anthraquinone Glycosides

• Upon hydrolysis, yields aglycones which are di, tri, or tetra hydroxyanthraquinones or a modifications of these compounds.

• The free anthraquinone aglycones exhibit little therapeutic activity as stimulant cathartics, and exert their action by increasing the tone of the smooth muscle in the wall of the large intestine

• Glycosides related to anthracene are present in such drugs as Cascara Sagrada, Frangula, Aloe, Rhubarb, Senna, Chrysarobin, Cochineal

• With the exception of Chrysarobin (too irritating) and Cochineal (A coloring agent); they are generally employed as cathartics

Anthraquinones | Borntrager’s Test

Appearance of orange-red compounds, soluble in hot water and in dilute alcohol. Gives a therapeutic red, violet, green, or purple color with a base

Anthraquinones | Frangula

• Common Name: Frangula

• Scientific Name: Rhamnus frangula

• Family Name: Rhamnaceae

• Constituents: Frangulin (Yellow crytalline glycoside), Thamnose (Isodulcite) and Frangula Emodin

• Use: Cathartic

Cyanogenetic Glycosides

• Also referred to as Cyanophoric Glycosides

• Yields HCN as one of the products of hydrolysis (by acid or enzyme)

• This group is represented by amygdalin, which is found in large quantities in bitter almonds, cherries, peaches, plums, and in many other seeds of the rosaceae family. And also in Prunasin, which occurs in Prunus serotina

• The common cyanophore glycosides are derivatives of mandelonitrile (benzaldehyde cyanohydrin)

Identification Test Cyanogenetic Glycosides | Guignard Test

• Using picrate paper, yellow to bring red or maroon coloration

• Plant glycosides extract treated with 5% alcoholic KOH + 2.5% FeCl₃. Heated to 70^oC. The, added to 20% HCl → Prusian Blue

• Plant Glycoside Extract + 3% HgNO₃ Solution → Black precipitate (due to metallic Hg)

Pharmaceutical/ Medicinal Uses of Cyanogenetic Glycosides

• Flavoring Agent

• Anticarcinogenic Drugs (Amygdalin-containing preparation known as Laetrile of Vit. B17)

• Control of Sickle Anemia

Saponin Glycosides

• Characterized by forming colloidal solutions in water, which foams upon shaking

• Possess bitter, acrid tastes

• Drugs containing saponins are usually sternmutatory (irritating to the mucous membrane)

• Destroys the RBC by hemolysis → Sapotoxins

• Upon hydrolysis, saponins yield aglycone known as sapogenin

Saponin Glycosides | Liebermann-Burchard Test

Blue to green coloration indicates the presence of unsaturated sterols and triterpenes with concentracted sulfuric acid

Isothiocyanate or Mustard Oil Glycosides

• These are sulfur-containing substances

  • Sinigrin → Black Mustard or Sinapis nigra (Brassica nigra)

  • Sinalbin → White Mustard or Sinapis alba (Brassica alba)

  • Gluconapin from Grape Seed

  • When hydrolyzed with myrosin (enzyme), they yield the mustard oils)

Isothiocyanate | White Mustard

• Common Name: White Mustard

• Scientific Name: Brassica alba

• Family Name: Brassicaceae

Isothiocyanate | Black Mustard

• Common Name: Black Mustard

• Scientific Name: Brassica nigra

• Family Name: Brassicaceae

Flavonol Glycosides

• Their aglycones are generally known as flavonoids (Yellow, Red, Violet, and Blue Pigment) widely distributed in higher plant kingdoms.

• Best Known Flavonoid Constituents:

  • Rutin

  • Quercitin

  • Citrus Flavonoids

    • Hesperidin

    • Hesperetin

    • Diosmin

    • Naringen

Test for Flavonoids | Bate-Smith and Metcalf Test

With concentrated acid a strong red or violet color indicates presence of leucoanthocyanidin

Test for Flavonoids | Wilstatter Cyanidin Test

With concentrated acid and Mg turning produces orange to red to crimson and magenta to green or blue indicated the presence of benzopyrone nucleus

Pharmaceutical/ Medicinal Uses of Flavonol Glycosides

• Rutin:

  • Called Vitamin P Factors since it has an effect on the permeability of the capillary blood vessels (capillary hemorrhagic)

• Citrus Bioflavonoids

  • Treating symptoms of common cold

• Dietary Supplements

• Flavonoids in Black Tea Beverage

  • Reduces the risk of heart attack

Alcohol Glycosides | Salicin

• Salicin is an alcoholic glycosides which hydrolyzes into Saligenins (Salicylic Alcohol)

  • Also used as anti-rheumatic

Alcohol Glycosides | Coniferin

A glycoside found in the cambial layer of pine trees, yielding coniferyl alcohol upon hydrolysis

Chemical Test for the Identification of Alcohol Glycosides | Ferric Chloride Test

Brown Coloration

Chemical Test for the Identification of Alcohol Glycosides | Sulfuric Acid Test

Red Coloration

Aldehyde Glycosides

• Vanillin → Aglycone found in Vanilla plantifolia (curing process)

  • A methylprotocatechoic aldehyde

  • Commonly used as flavoring agent

Aldehyde Glycosides | Vanilla

• Common Name: Vanilla or Vania bean

• Sceintific Name: Vanilla plantifolia

• Family Name: Glucovanillin and Glucovanillic Alcohol

• Uses: Flavoring agent and Perfumery

Aldehyde Glycosides | Japanese Star-Anise

• Common Name: Japanese Star-Anise

• Scientific Name: Illicium anisatum

• Family Name: Illiciaceae (Mag

Aldehyde Glycosides | Cantharides

• Common Name: Cantharides, Spanish Flies, Russian Flies, or Blisterinng Flies

• Scientific Name: Canthariss vesicatoria

• Family Name: Meloidae

• Constituent: Cathardin

• Uses: Irritant, Vessicant, Rubefacient

Phenol Glycosides

• The aglycone units of these glycosides are phenolic in character

• Examples:

  • Arbutin: Found in Uva ursi, chimaphila which yields hydroquinone and glucose upon hydrolysis

  • Hesperidin: Found in Citrus (which is also included in the flavonoid group)

Phenol Glycosides | Bearberry

• Common Name: Bearberry

• Scientific Name: Arctostaphylos uva-ursi

• Family Name: Ericaceae

• Constituents: Arbutin, Methyl Arbutin, Ericolin, Gallic Acid, Ellagic Acid, Quercetin and Tannins

• Use: Diuretic Agent and Astringent

Picrotoxin

• Convulsant Poison; Antidote for Barbiturate

• Also found in Anamirta cocculus → Central Stimulant

Crocus

Coloring and flavoring agent

Other Glycosides & Other Neutral Principles | Cocculus

• Common Name: Cocculus, Fishberry, Indian Berry

• Family Name: Menispermaceae

• Scientific Name: Anamirta cocculus

• Constituents: Picrotoxin

• Uses: CNS Stimulant, Antidote for Barbiturate Poisoning

Other Glycosides & Other Neutral Principles | Crocus

• Common Name: Crocus or Spanish Saffron

• Scientific Name: Crocus sativus

• Family Name: Iridaceae

• Constituent: Crocin

• Use: Coloring and Flavoring Agent