علم الأدوية والنباتات: مسار الحمض الشيكيمي

Pharmacognosy and Phytochemistry (Coumarins/Furanocoumarins/Chromones)

• Shikimic acid pathway is important for aromatic compounds.
• It's a precursor for aromatic amino acids (phenylalanine, tyrosine, tryptophan) biosynthesis in bacteria, fungi, and higher plants.
• It's a building block for alkaloids, coumarins, phenyl propanes, and volatile oils.
• The pathway is the starting point for tannins in all plants.
• It provides protection for plants against microorganisms.
• Shikimic acid is isolated from Illicium species (Japanese "shikimi," Japanese star anise).
• Oseltamivir phosphate (Tamiflu) is an antiviral drug that uses shikimic acid as a starting material.
• This drug is in high demand as defense against avian influenza (bird flu).
• The starting material for oseltamivir synthesis is (-)-shikimic acid.
• Shikimic acid is an important biochemical intermediate in plants and microorganisms.
• Currently, it's obtained via extraction or fermentation of genetically engineered Escherichia coli strains.

Coumarins

• Coumarins are derivatives of benzo-α-pyrone.
• They have a vanilla-like flavor.
• Coumarin is an oxygen heterocycle.
• They can be free or combined with glucose (coumarin glycoside).
• Coumarin's source is from the seeds of Dipteryx odorata (Tonka bean).
• Coumarins are used in perfumes and fabric conditioners.
• Some coumarins are hepatotoxic (harmful to the liver) in large doses.
• Coumarins include aesculetin, scopoletin, umbelliferone, and psoralens.
• Coumarins are organic solvents-soluble.
• They are derivatives of a-chromone, differing in benzene ring substitutions (OH, OCH3, CH3).
• Coumarins are commonly found in Apiaceae, Fabaceae, and Rutaceae families.
• Coumarins like Aesculin are found in the leaves, bark, and seeds of Aesculus hippocastanum (horse chestnut).
• Common uses include anti-inflammatory effects, and reducing capillary fragility.

Furanocoumarins (Photosensitizers)

• Furanocoumarins are commonly known as psoralens.
• Plants containing psoralens are used internally and externally to promote skin pigmentation and suntanning.
• Psoralens absorb near UV light and stimulate melanin pigment formation.
• The furan ring is derived from isopentyl pyrophosphate (mevalonic acid).
• Furanocoumarins (psoralens) interfere with DNA replication and reduce cell division rate.
• Methoxsalen (xanthotoxin, 8-methoxypsoralen) is used medically to treat vitiligo.
• Grapefruits contain bergamottin and 6',7'-dihydroxybergamottin.

Aflatoxins

• Aflatoxins are a group of mycotoxins produced by Aspergillus fungi.
• They are potent hepatotoxins and carcinogens in the liver.
• Aflatoxins contain a coumarin ring and an unsaturated lactone moiety.

Ammi visnaga

• The dried ripe fruit from this plant has been traditionally used for angina pectoris and bronchial asthma treatment in the Middle East.
• It has antispasmodic properties.
• It contains high amounts of furochromones.
• These furochromones include khellin, visnagin, khellol, and khellol glucoside.
• Khellin is coronary vasodilator and spasmolytic.
• Mixtures containing khellin, piperazine, and hexamine are antimicrobial agents for urinary tract infections.