From Wikipedia, the free encyclopedia
Methoxsalen also called xanthotoxin and metoxaleno (marketed under the trade name Oxsoralen , Dltasoralen , Meladinine) is a drug used to treat psoriasis, eczema, vitiligo, and some cutaneous Lymphomas in conjunction with exposing the skin to sunlight. Methoxsalen is extracted from Ammi majus, a plant of the family Umbelliferae. Methoxsalen modifies the way skin cells receive the UVA radiation, allegedly clearing up the disease. The dosage comes in 10mg tablets, which are taken in the amount of 30mg 75 minutes before a PUVA light treatment. The substance is also present in bergamot oil which is used in many perfumes and aromatherapy oils.
Risks and side effects
Patients with high blood pressure or a history of liver problems are at risk for inflammation and irreparable damage to both liver and skin. The eyes must be protected from UVA radiation. Side effects include nausea, headaches, dizziness, and in rare cases insomnia. When Eau de Cologne was made, it became a popular perfume. It contained bergamot oil as one of its components. Ladies wearing the perfume on places where the skin was radiated by the sun, noticed that their skin turned brownish at those spots. This is due to the phototoxic effects of methoxsalen present in the bergamot oil. The methoxsalen was removed, and most modern formulations of perfumes containing bergamot are de-methoxsalenised. When UVB light is used instead of UVA, there is no need to use any Psoralen (like Methoxsalen). The effect of the UVB light on the skin is strong enough and there is no need to increase the effect by using a Psorelen. Using UVB has the improvement that the side effects from the Psoralen are eliminated.
Cultural aspects
Author John Howard Griffin used the chemical to darken his skin in order to investigate racial segregation in the south. He wrote the non-fiction book Black Like Me about his experiences.[1]
Chemistry
The preparation of Methoxsalen starts with phosphorus oxychloride mediated acylation of pyrogallol, with chloroacetic acid to give the chloromethyl ketone. Treatment of that intermediate with potassium carbonate leads to the displacement of halogen by the phenoxide and the formation of a benzofuranone ring. The carbonyl group is then reduced catalytically to methylene to afford the benzodihydrofuran. That product is then allowed to react with malic acid in concentrated sulfuric acid. The overall reaction can be viewed as involving the initial decarboxylation of to give formylacetic acid. The enol from the latter then attacks the highly activated aromatic ring to give the cinnamic acid derivative (no stereochemistry implied). Internal esterification then completes formation of the coumarin and yields. The remaining free phenolic group is then treated with diazomethane and the resulting methyl ether dehydrogenated over palladium on charcoal. There is thus obtained methoxsalen.
References
- ^ Dead Like Me on snopes.com
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