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What are glycosides?
Compounds that yield one or more sugars upon hydrolysis.
Which of the following sugars is the most prevalent in natural glycosides?
Which type of glycoside is responsible for soap-like properties?
Cyanogenic glycosides liberate hydrocyanic acid upon hydrolysis.
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Match the following glycosides with their effects or properties:
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What is a common sugar found in anthraquinone glycosides?
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Name two aglycones derived from L-amino acids that are found in cyanogenic glycosides.
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The main purpose of cyanogenic glycosides in plants is to provide __________.
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Study Notes
Glycosides
- Compounds that yield one or more sugars upon hydrolysis.
- Composed of two parts:
- Sugar portion (glycone)
- Non-sugar portion (aglycone or genin)
- Many glycosides are formed from phenols, polyphenols, steroidal, and terpenoidal alcohols.
- Important pharmaceutically and medicinally.
Sugars in Glycosides
- D-glucose is the most prevalent sugar.
- L-rhamnose, D- and L-fructose, and L-arabinose are also common.
- Pentoses like L-arabinose are more common than D-xylose.
- Sugars often occur as oligosaccharides.
- The sugar moiety is attached to the aglycone via an oxygen atom (O-glycoside).
- Other bridging atoms include carbon (C-glycoside), nitrogen (N-glycoside), and sulfur (S-glycoside).
Classification of Glycosides
Based on Sugar Component
- Glycosides containing glucose are called glucosides.
- Glycosides containing fructose or galactose are called fructoside or galactoside, respectively.
Based on Aglycone
- Classified based on the structural types of aglycones present.
- Examples:
- Anthraquinone glycosides: aglycone is anthraquinone.
- Flavonoid glycosides: aglycone is flavonoid.
- Iridoid glycosides: aglycone is iridoid.
- Lignan glycosides: aglycone is lignan.
- Steroid glycosides: aglycone is steroid.
Based on Properties or Functions
- Saponins: glycosides with soap-like properties.
- Cyanogenic glycosides: glycosides that liberate hydrocyanic acid (HCN) on hydrolysis.
- Cardiac glycosides: glycosides that affect heart muscle.
Cyanogenic Glycosides
- Amygdalin, prunasin, and related glycosides liberate hydrocyanic acid upon hydrolysis.
- Aglycones are derived from L-amino acids:
- Amygdalin from L-phenylalanine.
- Linamarin from L-valine.
- D-hurrin from L-tyrosine.
- Found in the kernels of apricots, bitter almonds, cherries, plums, and peaches.
- Pharmaceutical uses:
- Flavoring agents.
- Amygdalin used in cancer treatment (HCN kills malignant cells) and as a cough suppressant.
- Toxicity:
- Excessive ingestion can be fatal.
- Improperly handled foodstuffs containing cyanogenic glycosides can cause poisoning (severe gastric irritations and damage).
- Test for HCN: Sodium picrate paper (yellow) turns red (sodium isopurpurate) in contact with HCN.
Anthracene/Anthraquinone Glycosides
- Aglycones belong to the structural category of anthracene derivatives.
- Most possess an anthraquinone skeleton and are called anthraquinone glycosides.
- Most common sugars are glucose and rhamnose.
- Colored substances with laxative and purgative properties.
- Anthraquinone aglycone increases peristaltic action of the large intestine.
- Found in various plant species, especially from Liliaceae, Polygonaceae, Rhamnaceae, Rubiaceae, and Fabaceae families.
- Biosynthesized in microorganisms like Penicillium and Aspergillus species.
- Commonly found as dimeric anthraquinone and their derivatives.
Sennosides
- Most important anthraquinone glycosides.
- Found in Senna leaves (Cassia angustifolia and Cassia senna).
- Contains two major sennoside glycosides:
- Sennosides A and B
- Other active components in Senna leaves:
- Rhein
- Aloe-emodin
Aloe Glycosides
- Found in aloe (Aloe barbadensis).
- Contain 2 major glycosides:
- Aloin A
- Aloin B
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Description
This quiz explores the fundamental concepts of glycosides, including their composition and classification based on sugar components and aglycone structure. Learn about the different types of sugars commonly found in glycosides and their importance in pharmacology and medicine.
