The Ability of Chlorophyll to Trap Carcinogen Aflatoxin B₁: A Theoretical Approach

The coordination of one and two aflatoxin B₁ (AFB₁, 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 AFB₁ and chl a molecules. The energy difference between molecular orbitals of AFB₁ and chl a allowed for the establishment of an intermolecular interaction. A charge transfer from AFB₁ 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 AFB₁. The complexes of maximum stability were chl a 1-α-E-AFB₁ and chl a 2-β-E-AFB₁, at -36.4 and -39.2 kcal/mol, respectively. Additionally, with two AFB₁ molecules were chl a 1-D-2AFB₁ and chl a 2-E-2AFB₁, at -60.0 and -64.8 kcal/mol, respectively. Finally, biosorbents containing chlorophyll could improve AFB₁ adsorption.