Classification of glycosides

Glycosides are a group of organic compounds in which a sugar (glycone) is chemically bonded to a non-sugar component (aglycone or genin) via a glycosidic bond. This bond is typically formed between the anomeric carbon of the sugar and a hydroxyl group, thiol group, or amine of the aglycone. Glycosides are widely distributed in nature and play important roles in various biological processes.

 

Classification of Glycosides

Glycosides can be classified based on different criteria:

1. Based on the Type of Sugar (Glycone):

   • O-Glycosides: The sugar is linked to the aglycone via an oxygen atom. Example: Amygdalin (found in bitter almonds).
   • N-Glycosides: The sugar is linked to the aglycone via a nitrogen atom. Example: Adenosine (a nucleoside in RNA).
   • S-Glycosides: The sugar is linked to the aglycone via a sulfur atom. Example: Sinigrin (found in mustard seeds).
   • C-Glycosides: The sugar is linked directly to the aglycone via a carbon-carbon bond. Example: Aloin (found in aloe vera).

2. Based on the Type of Aglycone:

   • Anthraquinone Glycosides: Contain anthraquinone as the aglycone. Example: Sennosides (found in Senna plants, used as laxatives).
   • Cardiac Glycosides: Contain steroids as the aglycone and are known for their ability to affect heart function. Example: Digitoxin (found in Digitalis species).
   • Flavonoid Glycosides: Contain flavonoids such as aglycone, which are pigments in plants. Example: Rutin (found in buckwheat and citrus fruits).
   • Coumarin Glycosides: Contain coumarin as the aglycone, known for their fragrance. Example: Aesculin (found in horse chestnut).
   • Saponin Glycosides: Contain sapogenin as the aglycone, which can form a soap-like foam when shaken in water. Example: Dioscin (found in yams).

3. Based on the Biological Activity:

   • Cardioactive Glycosides: These have a strong effect on heart muscle contraction. Example: Digoxin (used in treating heart failure).
   • Antibiotic Glycosides: These have antibiotic properties. Example: Streptomycin (used as an antibiotic).
   • Cyanogenic Glycosides: These release hydrogen cyanide upon hydrolysis. Example: Amygdalin (found in bitter almonds and apricot kernels).
   • Phenolic Glycosides: These have phenolic compounds such as aglycone, often with antioxidant properties. Example: Salicin (found in willow bark, precursor to aspirin).

Examples of Glycosides

1. Salicin: A phenolic glycoside found in willow bark, used historically as a pain reliever and precursor to aspirin.
2. Digitoxin: A cardiac glycoside derived from the foxglove plant, used in treating heart conditions.
3. Amygdalin: A cyanogenic glycoside found in bitter almonds, apricot seeds, and other plants, known for releasing cyanide upon hydrolysis.
4. Sennosides: Anthraquinone glycosides found in senna plants, are used as a laxative.
5. Streptomycin: An antibiotic glycoside used to treat bacterial infections, particularly tuberculosis.

Glycosides are essential in both plant physiology and pharmacology, with wide-ranging uses in medicine, industry, and agriculture.