Furocoumarins are naturally occurring chemical compounds produced by various plants. They are characterized by a specific chemical structure containing a furan ring fused with a coumarin nucleus. These compounds interact with environmental factors such as sunlight.
Where Furocoumarins Are Found
Furocoumarins are found in many common plants, particularly within certain botanical families. The Apiaceae family includes celery, parsley, parsnips, and dill. Members of the Rutaceae family, such as limes, lemons, oranges, and grapefruit, also contain these compounds. Figs from the Moraceae family are known to produce furocoumarins.
They function as a natural defense mechanism. When a plant is damaged or stressed, it can increase its production of furocoumarins. This chemical defense helps deter herbivores and protect the plant from fungal infections.
How Furocoumarins Affect the Body
The primary way furocoumarins interact with the human body involves a reaction with ultraviolet (UV) light, leading to phototoxicity. This interaction results in phytophotodermatitis, a skin reaction characterized by inflammation and damage. Symptoms appear hours to days after skin exposure to furocoumarin-containing plants and sun exposure. Initial signs include redness and a burning sensation, progressing to blistering in more severe cases.
The underlying mechanism involves furocoumarin molecules absorbing UVA radiation in skin cells. This absorption leads to an excited state, causing the compounds to bind to DNA within the skin cells. This binding disrupts normal cellular processes and can damage cell membranes and proteins. The cellular damage triggers an inflammatory response, manifesting as visible skin lesions. Following the acute phase, affected areas develop hyperpigmentation, where the skin darkens due to increased melanin production, which can persist for weeks or even months.
Medical Applications of Furocoumarins
Furocoumarins have therapeutic uses in medicine, most notably in PUVA therapy. This acronym stands for Psoralen plus UVA, where psoralen is a type of furocoumarin. In this procedure, the furocoumarin medication is administered, either orally or topically, to make the skin more sensitive to light. Following administration, the skin is exposed to a controlled dose of UVA light.
This combination therapy is employed to treat several skin conditions. Psoriasis, a chronic autoimmune disease causing rapid skin cell turnover, is managed with PUVA, as the treatment helps slow down cell growth. Vitiligo, a condition characterized by patches of skin losing their pigment, can also benefit from PUVA by stimulating repigmentation. Certain types of cutaneous lymphomas, which are cancers affecting the skin, are also treated with this method. PUVA therapy is a carefully monitored medical procedure performed under professional supervision, distinctly different from accidental environmental exposure.
Precautions and Management
Individuals can take several practical steps to minimize the risk of adverse reactions from furocoumarin-containing plants. When gardening or handling plants like celery, parsley, or parsnips, especially in sunny conditions, wearing protective clothing such as long sleeves and gloves can significantly reduce skin contact. Thoroughly washing any skin that has come into contact with these plants using soap and water immediately after exposure is advisable. Exercising caution when preparing or consuming certain fruits, like limes or lemons, outdoors where juice might get on the skin before sun exposure, is prudent.
If a skin reaction occurs, avoid further sun exposure to the affected area. Applying cool compresses or over-the-counter anti-inflammatory creams can help alleviate mild symptoms. For more severe reactions, such as extensive blistering or intense pain, seeking medical advice is recommended. A healthcare professional can assess the severity and provide appropriate treatment to manage the reaction and prevent complications.