HPLC with Electrochemical and Fluorescence Detection of the OPA/2-Methyl-2-propanethiol Derivative of Fumonisin B1

Chromatographic determination of the fumonisin mycotoxins

The fumonisins are a recently identified group of fungal toxins, occurring worldwide in naturally contaminated maize, which have elicited considerable attention over the past decade due to their association with the animal disease syndromes, equine leukoencephalomalacia and porcine pulmonary oedema, and their reported association with oesophageal cancer in rural areas of Transkei, South Africa and Linxian County, China. This paper reviews the development of sensitive chromatographic analytical methods for the determination of these toxins in a range of mainly maize or maize-based food matrices. Initial attempts at gas chromatographic determination of these toxins were supplanted by the successful development of liquid chromatographic methods based on solid-phase extraction (SPE) of solvent extracts, followed by precolumn derivatisation and HPLC determination using fluorescence detection. The most widely used method involves strong anion-exchange (SAX) SPE and the use of o-phthaldialdehyde as derivatising agent. In contrast, the development of thin-layer chromatographic methods enables large numbers of samples to be screened economically. The recent advances in liquid chromatography-mass spectrometry have resulted in the development of suitable methods for fumonisin analysis without the need of derivatisation.

Fumonisins, mycotoxins of increasing importance: their nature and their effects

The fumonisins (FBs) are a group of closely related mycotoxins that are prevalent in maize. They were isolated from strains of Fusarium moniliforme (Sheldon), which were implicated in the aetiology of human oesophageal cancer in the Transkei, South Africa. Their discovery explained the cause of equine encephalomalacia, or "hole in the head" syndrome, when it was found by feeding trials in horses that they elicited the disease. Subsequently, they were found to cause hepatic cancer in rats and pulmonary oedema in pigs, with most animal species tested showing liver and kidney damage. FB1 is the most important of the group and, although poorly absorbed from the gastrointestinal tract, its action is at the cellular level, affecting sphingolipid metabolism. Ceramides derived from sphingosine metabolism are cell regulatory factors affecting, among other things, DNA synthesis. Because FB1 has a close molecular resemblance to sphinganine, it interferes with ceramide biosynthesis and, hence, the processes that it regulates, which is thought to explain its carcinogenic properties. Studies on the FBs are still at a relatively early stage, but it is already clear that they play an important role in animal mycotoxicoses and, by implication, in human disease. A more positive aspect is that they will be used in elucidating the role of sphingolipids in cellular regulation.

Occurrence of fumonisins in the U.S. food supply

Over the past several years a great deal of interest has been shown in assessing human exposure to the fumonisins. This interest, of course, arises as a result of the finding of fumonisins in foods and the expanding data base on toxicological effects, both acute and sub-acute. The basis for exposure assessment lies in surveys of foods as well as a knowledge of consumption patterns. An overview of such surveys, limited as they are, will be presented along with some evaluation of the methodology used.

Quantitation and identification of fumonisins by liquid chromatography/mass spectrometry

A method was evaluated for the quantitation and identification of fumonisins by on-line liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization. A linear response in the full-scan mode with positive ion detection was obtained for fumonisin B1 (FB1) over the range of 5-5000 ng injected on-column. Purified FB1, FB2, and half-hydrolyzed FB1 showed equimolar responses. Fully hydrolyzed FB1 did not show a similar molar response profile and produced a signal which was approximately 2 times that obtained for an equal quantity of FB1. Most known fumonisins and preparative by-products such as methyl esters were chromatographically resolved and identified by MS by using an acetonitrile gradient and positive ion detection. Negative ion electrospray was used to differentiate fumonisin amides from esters on the basis of differences in response. Response factors for FB1 and the acetyl amide of FB1 in the negative ion mode at pH 4.5 were approximately 1:3, respectively.