This MedLibrary.org supplementary page on Phototoxin is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
Phototoxins are toxins that can cause allergic reactions in particularly susceptible individuals and which can cause dangerous photosensitivity 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 citruses contain essential oils that are photosensitisers;
- some herbal remedies (notably St John's wort, though incident rates for this plant are reportedly low);
- some prescribed medications (such as tetracycline antibiotics); and
- many essential oils, perfumes and cosmetics.
Ingested medications may cause systemic photosensitivity and topically applied medications, cosmetics and essential oils may lead to local (or perhaps systemic) photosenstivity. Curiously and ironically, para-aminobenzoic acid (PABA) found in some sunscreens can also cause photosensitivity.
Upon exposure to light, notably light containing ultraviolet 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. When exposed to near ultraviolet light, such as in sunlight, alpha-terthienyl generates the toxic singlet oxygen.[1] Alpha-terthienyl results in damage to the respiratory, digestive and nervous system of larvae, resulting in 100% death rates in concentrations of 33 ppb.[2] This makes it an interesting natural insecticide.
Rose bengal and other singlet oxygen generating phototoxins are also used in synthetic organic chemistry. They have also found use in photodynamic therapy, where the toxin is activated by intense light to destroy cancer cells.
References
- ^ J. Bakker, F. J. Gommers, I. Nieuwenhuis and H. Wynberg. Photoactivation of the nematicidal compound alpha-terthienyl from roots of marigolds (Tagetes species). A possible singlet oxygen role. JBC, Vol. 254, Issue 6, 1841-1844, Mar, 1979. http://www.jbc.org/cgi/content/abstract/254/6/1841
- ^ 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
See also
Wikipedia content modification information:
- This page was last modified on 15 October 2007, at 16:50.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Phototoxin".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.