Superoxide Scavenging Effects of Some Novel Bis-Ligands and Their Solvated Metal Complexes Prepared by the Reaction of Ligands with Aluminum Copper and Lanthanum Ions

摘要

Novel antioxidants have been synthesized and characterized by their chemical properties as antioxidants with high superoxide scavenging activity. (2R,3R)-diphenylethylenediamine is a spacer in antioxidants, and we synthesized targets >11a and >11b by conjugation with o-hydroquinone and p-hydroquinone at the two N-termini, respectively. Superoxide scavenging activities of the plant flavonoid-like >11a and >11b were compared with those of known antioxidants, and shown to increase in the following order: curcumin << ascorbic acid < Trolox < (+)-epicatechin < >11a < quercetin ° >11b. Compound >11a also formed a solvated >11a–metal complex with metal ions. The >11a–Cu²⁺ complex was shown to have higher superoxide scavenging activity than that of >11a, >11b, Cu²⁺, and the >11a–Al³⁺ and >11a–La³⁺ complexes, whereas the >11a–Al³⁺ complex increased rather than decreased superoxide levels. The >11a–Al³⁺ complex did not abstract one electron from the SOMO of O2>^−. since the HOMO and LUMO phases of Al³⁺ do not exist in the center of the >11a–Al³⁺ complex. However, the SOMO of the >11a–Cu²⁺ complex distributed in the center of Cu²⁺ may abstract one electron from the SOMO of O2>^−.. These results suggest that >11a and >11b are powerful antioxidants.