Fumonisin-ortho-phthalaldehyde derivative is stabilized at low temperature

摘要

Fumonisins are water soluble mycotoxins produced by the fungus Fusarium verticillioides (formerly F. moniliforme). Fumonisin B_1 (FB_1) 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 FB_1 (HFB_1). FB_1 and HFB_1 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) plus 2-mercaptoethanol (ME) reaction partner, however, the OPA-FB_1 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 FB_1 contribute to the instability of the OPA-FB_1 derivative. The results indicate that OPA-FB_1, OPA-FB_3 and OPA-HFB_1 derivatives are unstable at 24 °C but that their stability improves significantly at 4 °C. The OPA-sphinganine derivative is stable for at least 24 h at 24 °C. Thus, the instability of the OPA-FB1 derivative may be attributed to its lack of a hydroxyl group at the carbon 1 position.