Furanocoumarin

Furanocoumarins are a class of organic chemical compounds produced by a variety of plants. These compounds are known for their role in plant defense mechanisms and their effects on human health, particularly their phototoxic and photochemotherapeutic properties.

Structure and Classification

Furanocoumarins are derived from the fusion of a furan ring with a coumarin structure. The basic structure consists of a benzopyrone core with a furan ring attached. They are classified into two main types based on the position of the furan ring:

• Linear furanocoumarins: In these compounds, the furan ring is attached at the 6,7-position of the coumarin. Examples include psoralen, bergapten, and xanthotoxin.
• Angular furanocoumarins: Here, the furan ring is attached at the 7,8-position. Examples include angelicin and pimpinellin.

Biosynthesis

Furanocoumarins are synthesized in plants through the phenylpropanoid pathway. The biosynthesis begins with the amino acid phenylalanine, which is converted into cinnamic acid by the enzyme phenylalanine ammonia-lyase (PAL). Subsequent enzymatic reactions lead to the formation of umbelliferone, which is then modified to produce various furanocoumarins.

Occurrence

Furanocoumarins are found in several plant families, including Apiaceae, Rutaceae, and Moraceae. Notable plants containing these compounds include celery, parsley, citrus fruits, and figs.

Biological Activity

Furanocoumarins have several biological activities:

• Phototoxicity: When exposed to ultraviolet (UV) light, furanocoumarins can form covalent bonds with DNA, leading to cell damage and apoptosis. This property is utilized in PUVA therapy (psoralen + UVA) for treating skin conditions like psoriasis and vitiligo.
• Inhibition of Cytochrome P450: Some furanocoumarins, such as bergamottin found in grapefruit, can inhibit cytochrome P450 enzymes, affecting drug metabolism and leading to potential drug interactions.

Health Implications

While furanocoumarins have therapeutic applications, they can also pose health risks. Consumption of foods high in furanocoumarins, like grapefruit, can interfere with the metabolism of certain medications, leading to increased drug levels and potential toxicity. Additionally, handling plants containing furanocoumarins can cause phytophotodermatitis, a skin condition characterized by redness, blistering, and hyperpigmentation upon exposure to sunlight.

Also see

• Coumarin
• Psoralen
• PUVA therapy
• Phytophotodermatitis
• Cytochrome P450