718 Modern Food Microbiology STERIGMATOCYSTIN This mycotoxin is structurally and biologically related to the aflatoxins, and like the latter, it causes hepatocarcinogenic activity in animals At least eight derivatives are known Among the producing organisms are Aspergillus versicolor, A nidulans, A rugulosus, and others The LD50 for rats by intraperitoneal injection is 60–65 mg/kg Under UV light, the toxin fluoresces dark brick-red Although not often found in natural products, they have been found in wheat, oats, Dutch cheese, and coffee beans Although related to the aflatoxins, they are not as potent They act by inhibiting DNA synthesis FUMONISINS The fumonisins are produced by Fusarium spp on corn and other grains, and certain diseases of humans and animals are associated with the consumption of grains and grain products that contain high levels of these molds The species demonstrated to produce fumonisins include F sacchari, F subglutinans, F thapsinum, F globosum, F anthophilum, F dlamini, F napiforme, F nygami, F moniliforme, and F proliferatum.60 The latter species produces large quantities F moniliforme (formerly F verticilliodes; Gibberella fujikuroi) was the first to be associated with the mycotoxin and it is the best studied of the three The prevalence of F moniliforme is significantly higher in corn from areas where a high rate of human esophageal cancer occurred than in low esophageal cancer rate areas.54 There are at least 15 fumonisins, with the best known being FB1 , FB2 , FB3 , FB4 , FA1 , FA2 , and FA3 The major ones are FB1 –FB3 , and the others are considered to be minor and less well characterized Of the three major toxins, FB1 (also designated macrofusine) is produced in the largest quantities by producing strains For example, among nine strains of F moniliforme, the range of FB1 produced on autoclaved corn was 960 –2350 µg/g while for FB2 the range was 120–320 µg/g.72 Fusarin C is produced by F moniliforme but apparently is not involved in hepatocarcinogenic activity.35 It is mutagenic in the Ames test but only after liver fraction activation.98 In a culture medium, more was produced at pH 105 The incidence and prevalence of FB1 in corn and some corn products in six countries are summarized in Table 30–2 The highest levels found were in corn from an area in the Transkei, South Africa, where EC occurred at high rates The range for these six samples was 3020–117,520 ng/g with a mean of 53,740 ng/g.89 These levels exceeded those found in 12 samples of moldy corn from the same general area, where the mean was 23,900 ng/g.70 Overall, FB1 was found at lower levels in corn grits, while in corn meal levels tended to be higher (Table 30–2) Feed samples from 11 U.S states were examined for FB1 72 Of the 83 equine feeds that were associated with equine LEM, 75% contained >10 µg/g with a range of 10 µg/g with a range of