Phototoxins are

toxin A toxin is a naturally occurring poison produced by metabolic activities of living cells or organisms. They occur especially as proteins, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived ...

s that can cause allergic reactions in particularly susceptible individuals and which can cause dangerous

photosensitivity Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicit ...

in a much broader range of subjects. Phototoxins are common in: *a variety of plants (including food plants where they may be a biological defence): **many

citrus ''Citrus'' is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, mandarins, lemons, grapefruits, pomelos, and limes. ''Citrus'' is nativ ...

es contain

essential oil An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the ...

s that are photosensitizers; **some

herbal A herbal is a book containing the names and descriptions of plants, usually with information on their medicinal, Herbal tonic, tonic, culinary, toxic, hallucinatory, aromatic, or Magic (paranormal), magical powers, and the legends associated wi ...

remedies (notably St John's wort, though incident rates for this plant are reportedly low); **the carrot family of

Apiaceae Apiaceae () or Umbelliferae is a family of mostly aromatic flowering plants named after the type genus ''Apium,'' and commonly known as the celery, carrot, or parsley family, or simply as umbellifers. It is the 16th-largest family of flowering p ...

; *some prescribed medications (such as

tetracycline Tetracycline, sold under various brand names, is an antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis. It is available in oral an ...

antibiotics); and *many

essential oils An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the o ...

perfume Perfume (, ) is a mixture of fragrance, fragrant essential oils or aroma compounds (fragrances), Fixative (perfumery), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agre ...

s and

cosmetics Cosmetics are substances that are intended for application to the body for cleansing, beautifying, promoting attractiveness, or altering appearance. They are mixtures of chemical compounds derived from either Natural product, natural source ...

. Ingested medications may cause systemic photosensitivity and topically applied medications, cosmetics and essential oils may lead to local (or perhaps systemic) photosensitivity. Para-aminobenzoic acid ( PABA), found in some sunscreens, can also cause photosensitivity. Upon exposure to light, notably light containing

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

radiation, discolouration of the skin (whether as inflammation, lightening or darkening) or rashes may result. In extreme cases, blistering may also occur.

Uses

The marigold plant produces the phototoxin alpha-terthienyl, which functions as a

nematicide A nematicide is a type of chemical pesticide used to kill plant- parasitic nematodes. Nematicides have tended to be broad-spectrum toxicants possessing high volatility or other properties promoting migration through the soil. Aldicarb (Temik), a ...

. When exposed to near ultraviolet light, such as in sunlight, alpha-terthienyl generates the toxic

singlet oxygen Singlet oxygen, systematically named dioxygen(singlet) and dioxidene, is a gaseous inorganic chemistry, inorganic chemical with the formula O=O (also written as or ), which is in a quantum state where all electrons are Radical (chemistry), spin p ...

. Alpha-terthienyl results in damage to the respiratory, digestive and nervous system of larvae, resulting in 100% death rates in concentrations of 33 ppb.Manish Nivsarkar, Bapu Cherian and Harish Padh. Alpha-terthienyl: A plant-derived new generation insecticide. Current Science, Vol. 81, No. 6, 25 September 2001. http://www.ias.ac.in/currsci/sep252001/667.pdf This makes it an interesting natural insecticide.

Rose bengal Rose bengal (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) is a staining (biology), stain. Rose bengal belongs to the class of organic compounds called xanthenes. Its sodium salt is commonly used in eye drops to stain damaged conjuncti ...

and other

generating phototoxins are also used in synthetic organic chemistry. They have also found use in

photodynamic therapy Photodynamic therapy (PDT) is a form of phototherapy involving light and a photosensitizing chemical substance used in conjunction with molecular oxygen to elicit cell death ( phototoxicity). PDT is used in treating acne, wet age-related macula ...

, where the toxin is activated by intense light to destroy cancer cells.

Uses

References

See also