Phytochemical Analysis and Metal-chelation Activity of Achillea tenuifolia Lam.

Achillea tenuifolia Lam. (Asteraceae) afforded a dichloromethane fraction from which three known compounds β-sitosterol (compound1), 5-hydroxy, 4',6,7- trimethoxy flavone (salvigenin compound 2), and methyl-gallate (compound 3) were isolated for the first time. The structure of isolated compounds was elucidated by different spectroscopic methods. Applying the molar-ratio method, the complexation of salvigenin with Fe (III), Cu(II) and Zn(II), the most abundant type of metal ions in the body, were then evaluated. It was determined that stoichiometric ratio of salvigenin with these cations were as Fe(Salvigenin)2 (H2O)2 and Cu(Salvigenin)2(H2O)2 in methanolic solution without pH control, while zinc ions didn`t form significant complexes. The results were confirmed more, by computational molecular modeling of the structure of proposed ligand-complexes by semi-imperical PM3 calculations, which determined negative heat of formation for the complexes Fe(III) and Cu(II) ions as -689.7 and -573.5, respectively and proposed chelating affinity of salvigenin in the following order: Fe(III) > Cu(II) >> Zn(II).