Metabolites and Pathways Quiz

Primary Metabolites

• Primary metabolites are essential compounds produced by living organisms for growth and life.
• They are derived from sugars via primary metabolic pathways.
• Examples include sugars, lipids, amino acids, peptides, and proteins.

Secondary Metabolites

• Secondary metabolites are low molecular weight compounds.
• They are not essential for growth but are produced for adaptation and specific functions.
• They are considered a phenotype of the organism.
• They are derived from primary metabolites via secondary metabolic pathways.
• They are more important than primary metabolites as therapeutic agents.

Acetate-Malonate Pathway

• The pathway synthesizes fatty acids and aromatic metabolites.
• Key precursors are Acetyl-CoA and Malonyl-CoA.
• End products can be saturated or unsaturated fatty acids or polyketides.
• Polyketides are natural products synthesized by bacteria, fungi, and plants.

Anthraquinone Glycosides

• Most anthraquinone glycosides and aglycones are derived from the acetate pathway.
• They start from acetic acid units forming acetyl-CoA and then malonyl-CoA.
• The octa-β keto methylene chain loses CO2 and undergoes cyclization to form anthraquinones.
• Anthraquinones are important chemical groups with a large, aromatic structure.
• They are found in fungi, lichens, and plants.
• They are sparingly soluble in cold water but soluble in organic solvents and alcohols.
• Anthranol and antrone oxidation during plant storage increases laxative effects.

Glycosides

• Glycosides are compounds where an aglycone (non-sugar component) is linked to a sugar unit.

Anthraquinone Glycosides Types

• 1-O-glycosides: Glycone moiety is 1,8 dihydroxyanthraquinone.
  • Examples include Aloe-emodin-8-glycoside, Rhein-8-glycoside, and Chrysophanol-8-glycoside.
• 2-O-glycosides: Aglycone moiety is partially reduced 1, 8 dihydroxyanthraquinone.
  • Example includes Emodin-oxanthrone-9-glucoside
• 3-C-glycosides: Aglycone structure is an anthrone derivative.
  • Example includes Aloin
• 4-C- and O-glycosides: Include Cascarosides A&B (barbaloin/aloin) and Cascarosides C&D (chrysaloin).

Pharmacologic Actions of Anthraquinones

• They are stimulant cathartics that increase colon smooth muscle tone and water/electrolyte secretion.
• Hydrolysis in the colon results in active aglycones that act within 8-12 hours.
• They are used to treat constipation and to prepare for procedures requiring bowel evacuation.

Adverse Effects of Anthraquinones

• Long-term use or high doses can cause severe adverse effects, like laxative dependence, hypokalemia, albuminuria, hematuria, heart arrhythmia, nephropathy, edemas, and accelerated bone deterioration.
• Colon lining can take on a dark brownish-black hue (melanosis coli), increasing cancer risk.
• Should not be used in cases of dehydration, diarrhea, or loose stools.

Uses

• Important laxative agents
• Used in the treatment of constipation.
• Used for bowel evacuation prior to medical procedures.

Plant Sources

• Senna ( Cassia acutifolia and Cassia angustifolia)
• Aloe (Aloe barbadensis)
• Cascara sagrada (Frangula purshiana)
• Rhubarb (Rheum palmatum)

Additional Notes

• There are various chemical compounds within these plant families that are relevant and useful in treatment

Chemistry of Compounds

• Chemical structures for specific anthraquinones, glycosides, and their related compounds are described.