Inhibitory mechanism of mimosa tannin using molecular modeling and substitutional adsorption isotherms

A semiempirical approach involving quantum chemical calculations was used to rationalize the mimosa tannin inhibitory action. The molecular spatial structure, atomic charges, dipole moment, HOMO–LUMO energy gap and HOMO density of four types of flavanoid units that constitute mimosa tannin, have been theoretically investigated using HyperChem 5.11 computer package. Optimization of the molecular geometry yielded a non-planar structure with the electron charge density distributed non-uniformly. The HOMO–LUMO energy gap was used to determine the electron donating ability of the molecule. The highest values of the HOMO density was found in the vicinity of the functional groups indicating them as most probable adsorption centers.