Psoralene

Psoralen is a naturally occurring organic compound belonging to the furanocoumarin class. It is found in various plants, notably in the seeds of Psoralea corylifolia (bu gu zhi) and in certain citrus fruits like bergamot, grapefruit, and limes. Psoralen is known for its photosensitizing properties, meaning it can absorb ultraviolet (UV) radiation.

When psoralen is applied to the skin and then exposed to UV-A light, it can form covalent bonds with DNA. This interaction can damage DNA and inhibit cell replication. This property is exploited in photochemotherapy, a medical treatment for certain skin conditions like psoriasis, eczema, and vitiligo. In this treatment, psoralen is administered orally or topically, followed by exposure to controlled doses of UV-A light (PUVA therapy).

However, psoralen can also cause adverse effects. Skin exposure to psoralen without subsequent UV light exposure can lead to phytophotodermatitis, a rash that appears on sun-exposed skin. This reaction is characterized by redness, blistering, and hyperpigmentation. Due to its photosensitizing nature, it is important to handle psoralen with care and avoid direct sunlight after exposure. Research continues to explore the therapeutic potential and mechanisms of action of psoralens.