FORMATION OF N-(CARBOXYMETHYL)FUMONISIN B-1, FOLLOWING THE REACTION OF FUMONISIN B-1 WITH REDUCING SUGARS

The fumonisins are mycotoxins produced by fungi that contaminate prima rily corn and are toxic through interruption of intracellular sphingol ipid synthesis. Several reports have indicated that fumonisin B-1 conc entrations decreased when heated in aqueous solutions of reducing suga rs. The incubation of fumonisin B1 with D-glucose resulted in the form ation of N-(carboxymethyl)fumonisin BL, which was characterized by NMR and electrospray mass spectroscopy. We determined the methylene carbo n of the carboxymethyl group is derived from C1 on glucose, while the carbonyl carbon is derived from the C2 of glucose, using C-13 glucose. Apparently N-(carboxymethyl)fumonisin B1 arises from Schiffs base for mation, Amadori rearrangement to a B-ketoamine, and oxidation with mol ecular oxygen. N-(Carboxymethyl)fumonisin B1 formation is favored by a lkaline conditions (pH > 7), requires molecular oxygen, and is catalyz ed by several reducing sugars. N-(carboxymethyl)fumonisin B-1 was dete cted in raw corn samples that contained fumonisin B-1 (0.5-1.4 ppm) at an average of 4% of the fumonisin B-1 levels.