[Study on the Antioxidant Activity of Aloe-Emodin Metal Complex]

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.