Abstract
Employing theoretical calculations with density functional theory (DFT) using the B3LYP/6-311++G(d,p) functional and basis set, the interaction of the aflatoxin B1 (AFB1) molecule and the functional groups present in the Pyracantha koidzumii biosorbent was investigated. Dissociation free energy and acidity equilibrium constant values were obtained theoretically both in solution (water) and gas phases. Additionally, the molecular electrostatic potential for the protonated molecules was calculated to verify the reactivity. Thus, methanol (hydroxyl group), methylammonium ion (amino group), acetate ion (carboxyl group), and acetone (carbonyl group), were used as representatives of the substrates present in the biomass; these references were considered using the corresponding protonated or unprotonated forms at a pH value of 5. The experimental infrared spectrophotometric data suggested the participation of these functional groups in the AFB1 biosorption process, indicating that the mechanism was dominated by electrostatic interactions between the charged functional groups and the positively charged AFB1 molecule. The theoretical determination indicated that the carboxylate ion provided the highest interaction energy with the AFB1 molecule. Consequently, an enriched biosorbent with compounds containing carboxyl groups could improve the yield of the AFB1 adsorption when using in vitro and in vivo trials.
Highlights
Aflatoxins (AFs) are biologically active secondary metabolites from certain fungal strains of Aspergillus flavus Link, A. parasiticus Speare and A. nomius Kurtzman et al [1,2], being potentially fatal to humans and animals [3,4]
The biosorption model was proposed to be dominated by electrostatic interactions between the positively charged Aflatoxin B1 (AFB1) molecules and the hydroxyl, ammonium, carboxylate and ketone-carbonyl groups of the biosorbent molecules
Others authors have reported the protonation of the AFB1 molecule on the oxygen atom of the carbonylic groups (O12, O14 ), furan ring (O7 ), methoxyl group (O13 ) and the lactone ring (O10 ) [9,12,18], which is consistent with our findings
Summary
Aflatoxins (AFs) are biologically active secondary metabolites from certain fungal strains of Aspergillus flavus Link, A. parasiticus Speare and A. nomius Kurtzman et al [1,2], being potentially fatal to humans and animals [3,4]. Reducing the consumption of aflatoxin-contaminated foods significantly minimizes the risk of an acute or chronic aflatoxicosis in humans; in developing countries such as Mexico, this scheme is not easy to achieve, due to the fact that the Mexican population has one of the highest world per capita consumption of maize, frequently contaminated with aflatoxins, both in the field as well as in storage [7]. Various methods have been investigated in connection with their effectiveness to control AF, with the objectives to either inactivate, to degrade, or to remove the mycotoxin, and they can be classified into physical, chemical, and biological [8,9,10,11,12,13]
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