Phototoxicity

Phototoxicity, also called photoirritation, is a chemically induced skin irritation, requiring light, that does not involve the immune system. It is a type of photosensitivity. The skin response resembles an exaggerated sunburn. The involved chemical may enter into the skin by topical administration, or it may reach the skin via systemic circulation following ingestion or parenteral administration. The chemical needs to be "photoactive," which means that when it absorbs light, the absorbed energy produces molecular changes that cause toxicity. Many synthetic compounds, including drug substances like tetracyclines or fluoroquinolones, are known to cause these effects. Surface contact with some such chemicals causes photodermatitis, and many plants cause phytophotodermatitis. Light-induced toxicity is a common phenomenon in humans; however, it also occurs in other animals. A phototoxic substance is a chemical compound which becomes toxic when exposed to light. Some medicines: tetracycline antibiotics, sulfonamides, amiodarone, quinolones, psoralen Many cold pressed citrus essential oils such as bergamot oil Some plant juices: parsley, lime, and Heracleum mantegazzianum Porphyrins, a class of natural molecules occurring in the body and accumulating in patients with certain genetic disorders in the building chain of the red blood dye heme: porphyria Phototoxicity is a quantum chemical phenomenon. Phototoxins are molecules with a conjugated system, often an aromatic system. They have a low-lying excited state that can be reached by excitation with visible light photons. This state can undergo intersystem crossing with neighboring molecules in tissue, converting them to toxic free radicals. These rapidly attack nearby molecules, killing cells. A typical radical is singlet oxygen, produced from regular triplet oxygen. Because free radicals are highly reactive, the damage is limited to the body part illuminated.

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Bergamot orange

Citrus bergamia, the bergamot orange (pronounced ˈbɜrɡəmɒt), is a fragrant citrus fruit the size of an orange, with a yellow or green color similar to a lime, depending on ripeness. Genetic research into the ancestral origins of extant citrus cultivars found bergamot orange to be a probable hybrid of lemon and bitter orange. Extracts have been used as an aromatic ingredient in food, tea, snus, perfumes, and cosmetics. Use on the skin can increase photosensitivity, resulting in greater damage from sun exposure.

Phytophotodermatitis

Phytophotodermatitis, also known as berloque dermatitis or margarita photodermatitis, is a cutaneous phototoxic inflammatory reaction resulting from contact with a light-sensitizing botanical agent followed by exposure to ultraviolet light (from the sun, for instance). Symptoms include erythema, edema, blisters (vesicles and/or bullae), and delayed hyperpigmentation. Heat and moisture tend to exacerbate the reaction. A reaction may be elicited in any person who has been exposed to adequate amounts of both a photosensitizer and ultraviolet light.

Psoralen

Psoralen (also called psoralene) is the parent compound in a family of naturally occurring organic compounds known as the linear furanocoumarins. It is structurally related to coumarin by the addition of a fused furan ring, and may be considered as a derivative of umbelliferone. Psoralen occurs naturally in the seeds of Psoralea corylifolia, as well as in the common fig, celery, parsley, West Indian satinwood, and in all citrus fruits.

Maltol-Derived Ruthenium-Cymene Complexes with Tumor Inhibiting Properties: The Impact of Ligand-Metal Bond Stability on Anticancer Activity In Vitro

Christian Hartinger, Alexey Nazarov

Organometallic rutheniumarene compounds bearing a maltol ligand have been shown to be nearly inactive in in vitro anticancer assays, presumably due to the formation of dimeric Ru-II species in aqueous solutions. In an attempt to stabilize such complexes, [ ...

2009

Importance of fluence rate in photodynamic therapy with ALA-induced PpIX and BPD-MA in a rat bladder tumor model

Georges Wagnières

Oxygen dependent phototoxicity was investigated in vivo in an orthotopic rat bladder tumor model. Two photosensitizers, benzoporphyrin derivative monoacid ring A and 5-aminolevulinic acid-induced protoporphyrin IX were studied. For a given cumulative light ...

1995