Submitted to: Journal of Chromatography A
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2004
Publication Date: 4/24/2004
Citation: Williams, L.D., Meredith, F.I., Riley, R.T. 2004. Fumonisin- ortho-phthalaldehyde derivative is stabilized at low temperature. Journal of Chromatography B. 806:311-314. Interpretive Summary: Fumonisins are toxic chemical that are produced by a mold known as Fusarium verticillioides. The toxic chemicals produced by this mold dissolve easily into water. There are approximately 28 different forms of the toxic chemical but the most common form is called fumonisin B1. When fumonisin B1 is treated with alkali solutions, as happens during certain cooking processes, it loses some of its parts that are the most highly charged. When this happens it is called "hydrolyzed" fumonisin B1. Both fumonisin B1 and hydrolyzed fumonisin B1 resemble a natural fat known as sphinganine. Sphinganine is different than either fumonisin B1 or hydrolyzed fumonisin B1 in that it has an oxygen atom on the first carbon of the carbon backbone. These three chemicals are all detected by the same analytical procedure using a chemical known as ortho-phthalaldehyde (OPA), however, the product of combining fumonisin B1 and OPA is not stable at room temperature. The objectives of this study were to 1) determine the effect of temperature on the stability of the OPA-fumonisin B1 product and 2) determine which chemical property of fumonisin B1 causes the instability of the OPA-fumonisin B1 product. The results of this study show that the OPA-fumonisin B1 and OPA-hydrolyzed fumonisin B1 products are not stable at 24 degrees C but that their stability improves significantly at 4 degrees C. The OPA-sphinganine product is stable for at least 24h at 24 degrees C. Thus, the instability of the OPA-fumonisin B1 product may be due to its lack of chemical groups on the first carbon and possibly the presence of additional chemical groups on the carbon backbone of fumonisins.
Technical Abstract: Fumonisins are water soluble mycotoxins produced by the fungus Fusarium verticillioides (formerly F. moniliforme). Fumonisin B1 (FB1) is a diester of propane-1,2,3-tricarboxylic acid and 2-amino-12, 16-dimethyl-3,5,10,14,15-pentahydroxyeicosane, and is the most abundant of the naturally occurring fumonisins. Upon removal of the two tricarballylic acid side chains, the structure is referred to as hydrolyzed FB1 (HFB1). FB1 and HFB1 are structurally similar to sphinganine, a sphingoid base. The fumonisins do not absorb UV light or fluoresce; therefore, derivatizing reagents are used for detection when separation is by high performance liquid chromatography (HPLC). The standard derivatizing reagent used for HPLC is ortho-phthalaldehyde (OPA), however, the OPA-FB1 derivative is not stable at room temperature. The objectives of this study were to 1) determine the effect of temperature on the stability of the OPA-FB1 derivative and 2) determine which structural characteristics of FB1 contribute to the instability of the OPA-FB1 derivative. The results indicate that OPA-FB1 and OPA-HFB1 derivatives are unstable at 24 degrees C but that their stability improves significantly at 4 degrees C. The OPA-sphinganine derivative is stable for at least 24 h at 24 degrees C. Thus, the instability of the OPA-FB1 derivative may be attributed to its lack of a hydroxyl group at the 1 position and possibly the presence of additional hydroxyls on the hydrocarbon backbone.