Study on the Antioxidant Activity of Aloe-Emodin Metal Complex

Abstract

To synthesize three kinds of metal complexes of aloe-emodin and compare the antioxidant activities of the ligands and the complexes. Three kinds of aloe emodin metal complex, the aloe-emodin-iron (Ⅱ), the aloe-emodin-copper (Ⅱ) and the aloe-emodin-magnesium (Ⅱ) complexes, were synthesized by dissolving and stirring in anhydrous ethanol solvent, and their structures were characterized. The Fe 2+-H 2O 2-methylene blue method, the diphenyl bitter hydrazine radical method (DPPH method) and other assays were used to determine the clearance effect of ligands and complexes on superoxide radicals (O 2 －•), hydroxyl radicals (•OH) and phenyl bitter hydrazine radical (DPPH•). Three kinds of aloe emodin metal complex, the aloe-emodin-iron (Ⅱ), the aloe-emodin-copper (Ⅱ) and the aloe-emodin-magnesium (Ⅱ) complexes, were successfully synthesized. According to the results of structural characterization, we speculated that the aloe-emodin metal complexes were formed at the site between the two molecules of aloe-emodin and one molecule of metal ions (Fe 2+, Mg 2+, Cu 2+) via the 9 th carbonyl and 8 th hydroxyl groups of the aloe-emodin molecules. Both the complex and the ligand have clearance effects on three kinds of free radicals, and the complex showed stronger effects than its ligand ( P<0.05). Coordination of aloe-emodin with metal ions, such as Fe 2+, Cu 2+, and Mg 2+, could enhance the antioxidant activity of the ligand itself.