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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT AND EVALUATION OF IMPROVED MATERIALS FOR MYCOTOXIN ANALYSIS

Location: Bacterial Foodborne Pathogens & Mycology Research Unit

Title: Photolysis of Cyclopiazonic Acid to Fluorescent Products

Author
item MARAGOS, CHRIS

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 7, 2008
Publication Date: November 7, 2008
Citation: Maragos, C.M. 2008. Photolysis of Cyclopiazonic Acid to Fluorescent Products [abstract]. 43rd Toxic Microorganisms Joint Panel. p. 14.

Technical Abstract: Cyclopiazonic acid (CPA), which is produced by certain species of Aspergillus and Penicillium, can co-occur with aflatoxins under certain conditions. A large proportion of A. flavus strains can produce CPA and it has been found as a natural contaminant in cheeses, corn, rice, peanuts, millet and feeds. In test animals CPA is capable of causing disease symptoms, which are believed to be the result of the disruption of calcium homeostasis. Previously an acceptable daily intake of CPA has been estimated as 10 µg/kg body weight/day. Cyclopiazonic acid is a substituted indole with a molecular weight of 336.38. The molecule has a chromophore with absorptions in the ultraviolet (UV) region at 223 nm and 278 nm. Generally the isolation of CPA from commodities has been somewhat tedious and has been based upon liquid-liquid partitioning followed by solid phase extraction (SPE). A simpler immunoaffinity column approach has also been described but the columns are not commercially available. Following extraction and isolation further separation using high performance liquid chromatography with UV detection (HPLC-UV) has been commonly used for measurement of CPA. Thin layer chromatography, mass spectroscopy, Fourier transform mid-infrared ATR spectroscopy, and immunoassay methods for detection of CPA have also been reported. Previous descriptions of the physical properties of CPA have not suggested the molecule has a native fluorescence. However, during the development of analytical methods for CPA we discovered an interesting phenomenon, namely that the non-fluorescent CPA could be made fluorescent following exposure to a high intensity UV light in a photochemical reactor. We exposed CPA to UV light in either a static mode (ie in a cuvette) or in a continuous mode (ie as a post-column photolysis of HPLC eluant). Upon exposure to UV light the absorbances at 223 nm and 278 nm both declined while fluorescence increased. In methanol or aqueous acetonitrile the products of photolysis had an excitation maximum of 372 nm and an emission maximum of 462 nm. In the static exposure mode the maximum fluorescence was obtained after exposure for 30 min for CPA or 5 min for aflatoxin B1 (AFB1). HPLC with post-column photolysis of CPA and AFB1 was accomplished which permitted the fluorescence detection of both toxins. The ability to photolyze CPA and detect this toxin by fluorescence may open up new ways to measure this mycotoxin alone or together with the aflatoxins.

Last Modified: 9/10/2014
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