Theoretical study on the structure and properties of crenulatin molecule in herb Rhodiola crenulata

Crenulatin (C25H20O10) is a flavonol derivative, which can be isolated from the roots of Rhodiola crenulata (Hook. F. et Thoms.), a widely used medicinal herb due to its nice curative effect. In this study, theoretical analysis on the geometries and electronic properties of its molecular structure (crenulatin-a or crenulatin-b diastereoisomers) in gas phase is reported. As judged by total energy, the frontier orbital energy gap, the maximum hardness principle and 13C chemical shifts, we predict that crenulatin-a structure is the preferable structure of crenulatin molecule. Both diastereoisomers are soluble in water which enhances its biological activity of antioxidant. In order to evaluate the antioxidant activity of the molecule, the best indicators of the antioxidative, the O-H bond dissociation enthalpy (BDE) and adiabatic ionization potential (IP) were computed by density functional theory (DFT). We obtained that the most active site is the 3-OH group and crenulatin is active as an electron donor. All these results suggest that crenulatin is a potential antioxidant similar to kaempferol.