A DFT Study on the Radical Scavenging Activity of Hydroxyanthraquinone Derivatives in Rhubarb

The structural and electronic properties of hydroxyanthraquinone derivatives in rhubarb, namely, chrysophanol, emodin, physcion, aloe-emodin, rhein, and their radicals were investigated at density functional level. The bifurcated hydrogen bond property of the studied structures was investigated using the atoms in molecules theory. It turned out that the presence of the dihydroxy functionality increases the radical stability through hydrogen bonds formation and favors hydrogen atom abstraction. Bond dissociation energy and ionization potential were also determined to know if the radical scavenging activity of these compounds proceeds via an H-atom or an electron-transfer mechanism. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111: 1064-1071, 2011