The Study On Fumonisin B₁ And B₂ Contaminations In Corn From Three Provinces Of Liaoning, Shandong And Henan

Fumonisins(FBs) are carcinogenic mycotoxins produced by Fusarium verticillioides and Fusarium proliferatum as secondary metabolites. FBs have not only been shown to induce the fatal disease syndromes: equine leukoencephalomalacia and porcine pulmonary edema, but also have been linked with an increased risk of esophageal cancer in humans. Based on their toxicity, FB₁ has been classified by International Agency for Research on Cancer (IARC) as possibly carcinogenic in humans (Group 2B).An analytical method of determination of fumonisins B₁ and B₂ in corn,by high performance Iiquid chromatograph post-column derivatization(HPLC-post-column derivatization) was developed. Incidence and level of fumonisins B₁ and B₂ in corn in Liaoning, Shandong and Henan provinces were studied. Furthermore, this study were to evaluate the effect of temperature and co-inoculation of Fusarium graminearum on production of fumonisins B₁ and B₂ by strains of F. verticillioides and F. proliferatum. The results of study were as follows:FB₁and FB₂ were extracted with acetonitrile-water and cleaned up by SAX column. After separation with C₁8 column, and derivatization with OPA and 2-mercaptoethanol, fumonisins B₁ and B₂ were determined by fluorimetric detection to overcome some disadvantages of pre-column derivatization, such as instability of fluorescent derivatives, low sensitivity, use of toxic reagents.The study was undertaken to evaluate the natural occurrence of fumonisins B₁ and B₂ in corn from Liaoning, Shandong and Henan provinces. Fumonisin levels in the three studied provinces varied from region to region in occurrence and mean. This detectable spread of fumonisin was high in Liaoning (80.0% for FB₁ and 54.3% for FB₂) when compared to Shandong (40.5% for FB₁ and 27.4% for FB₂) and Henan provinces (42.6% for FB₁ and 18.8% for FB₂). 45.7% of tested samples from Liaoning had total fumonisins concentration exceed the American limits of 2000μg/kg. In Shandong and Henan provinces 12 of 84 (14.3%) and 8 of 101 (7.9%) samples, respectively, had total fumonisins levels >2 000μg/kg. The mean concentrations in this study for the corn samples from Liaoning, Shandong and Henan province were 3990, 845 and 665μg/kg, respectively.In vitro, 23 strains (F. proliferatum) isolated from corn samples Liaoning were studied for their capability to produce FB₁ (12.0～3626.7 mg/kg) and FB₂ (1.3～654 mg/kg). All 23 strains used in this study produced FB₁ and FB₂ on corn kernels. In these strains, 56.5% were high producers (≥500 mg/kg). Their capability to produce FB₁ and FB₂ was diverse for different strains. All strains produced relatively high levels of FB₁ than FB₂.A variety of toxins were detected in moldy corn from different areas. Distribution of DON, ZEN, FB₁ and FB₂ levels were varied in moldy corn. AFs were not detected in corn in our study.Preliminary study was to evaluate the effect of temperature and co-inoculation of F. graminearum on production of fumonisins B₁ and B2 by strains of F. verticillioides and F. proliferatum. At certain water activity (aw), the capability of F. verticillioides and F. proliferatum to produce FB₁ and FB₂ was significantly affected by temperature. 20℃, was optimum for production of FB₁ and FB₂ for F. verticillioides and F. proliferatum. Two strains produced less FB₁ and FB₂ when the temperature increasing. FB₁ and FB₂ produced by F. verticillioides and F. proliferatum shown a obvious trend to inhibited by F. graminearum at 20℃. In the presence of F. graminearum, FB₁ and FB₂ production by F. proliferatum were increased at 25℃and 30℃,however,the effect on F. verticillioides was not significant.