Density functional theoretical study on attachment sites of Mg2+ and Ca2+ and metal ion affinity to Crenulatin molecule

Crenulatin (C25H20O10) is a flavonol derivative and has been isolated from the roots of Rhodiola crenulata (Hook. F. et Thoms.), a widely used medicinal herb. Magnesium and calcium cations play an important physiological role in biological systems. In this work, interactions of magnesium and calcium divalent cations with Crenulatin molecule were studied. Density functional theory (DFT) was used to determine coordination geometries and absolute metal ion affinities (MIA) for all possible stable complexes. The results show that calcium and magnesium cations are able to interact with the Crenulatin molecule through mono-, bi-, and tricoordination. B3LYP/6-31G(d) bond energies for all complexes reveal that magnesium cation has a greater affinity to Crenulatin molecule than calcium cation. The calculated value of Mg2+ cation affinity, including the zero-point vibrational energy (ZPE) and basis set superposition error (BSSE), is 231.8 kcal mol(-1) for the most stable complex. Entropy (Delta S) and free energy (Delta G) variations for the metalation processes considered here have also been reported.