Transformation of Adsorbed Aflatoxin B1 on Smectite at Elevated Temperatures

Aflatoxins cause liver damage and suppress immunity. Smectites can be used to reduce the bioavailability of aflatoxins through adsorption. To further reduce the toxicity of aflatoxins and to eliminate the treatments of aflatoxin-loaded smectites, degrading the adsorbed aflatoxin to nontoxic or less toxic compounds would be desirable. The objective of this study was to investigate the effects of temperature and exchange cation on the transformation of adsorbed aflatoxin B1 on smectite. An AfB1-Casmectite (sm) complex was synthesized. To enhance the Lewis acidity of the complexes, the exchange calcium in the complex was replaced with manganese (Mn) and copper (Cu) to obtain AfB1-Mn-sm and AfB1-Cu-sm complexes, respectively. The aflatoxin-sm complexes and pure aflatoxin B1 were dried at 60 oC in aluminum cups, and heated from 100 to 200 C using 25 C steps. Aflatoxin B1 and its transformation products were extracted with methanol after the heating treatment. The extracts were analyzed with UV spectroscopy, high performance liquid chromatography (HPLC)-fluorescence/UV, ultra performance liquid chromatography (UPLC)-photodiode array (PDA) and electrospray ionization-tandem quadrupole-mass spectrometry (ESI-TQDMS). The solid residues were analyzed with Fourier transform infrared spectroscopy (FTIR). The UV and FTIR spectra of the AfB1-sm clay residue extracts obtained after heating had decreased AfB1 peak intensities and shifted peak positions with increased heating temperature. Prominent shifts in band positions and shape of the UV spectra were observed in the extracts from 175 C heated AfB1-Ca-sm complex, 150 C heated AfB1-Cu-sm complex, and 125 C heated AfB1-Mn-sm complex. The HPLC and UPLCMS analyses of AfB1-sm complex extracts indicated a gradual fB1 concentration decrease with increased heating temperature and the formation of aflatoxins B2, B2a, M1, M2, and other unidentified compounds. No new compound was observed in the extracts of pure aflatoxin B1 after a comparable heating experiment. These results suggest that smectite can effectively convert aflatoxin to other less toxic forms at elevated temperatures. Smectite ion exchange with Cu or Mn Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation transition metals cations and heat treatment induced more efficient conversion of the adsorbed aflatoxin B1 molecules to other compounds.