The Ability of Chlorophyll to Trap Carcinogen Aflatoxin B(1): A Theoretical Approach

The coordination of one and two aflatoxin B(1) (AFB(1), a potent carcinogen) molecules with chlorophyll a (chl a) was studied at a theoretical level. Calculations were performed using the M06-2X method in conjunction with the 6-311G(d,p) basis set, in both gas and water phases. The molecular electrostatic potential map shows the chemical activity of various sites of the AFB(1) and chl a molecules. The energy difference between molecular orbitals of AFB(1) and chl a allowed for the establishment of an intermolecular interaction. A charge transfer from AFB(1) to the central cation of chl a was shown. The energies of the optimized structures for chl a show two configurations, unfolded and folded, with a difference of 15.41 kcal/mol. Chl a appeared axially coordinated to the plane (α-down or β-up) of the porphyrin moiety, either with the oxygen atom of the ketonic group, or with the oxygen atom of the lactone moiety of AFB(1). The complexes of maximum stability were chl a 1-α-E-AFB(1) and chl a 2-β-E-AFB(1), at −36.4 and −39.2 kcal/mol, respectively. Additionally, with two AFB(1) molecules were chl a 1-D-2AFB(1) and chl a 2-E-2AFB(1), at −60.0 and −64.8 kcal/mol, respectively. Finally, biosorbents containing chlorophyll could improve AFB(1) adsorption.