title: 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.
abstract: 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.
authors.affiliation: Division of Analytical Chemistry of Medicines, Showa Pharmaceutical University, 3-3165 Higashitamagawagakuen, Machida, Tokyo 194-8543, Japan. kobayasi@ac.shoyaku.ac.jp
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Sachi
authors.initials: S
authors.lastname: Kanai
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry* / Q000494:pharmacology; D003300:Copper / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000737:chemistry* / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D007811:Lanthanum / Q000737:chemistry*; D008024:Ligands; D008956:Models, Chemical; D008968:Molecular Conformation; D013481:Superoxides / Q000037:antagonists & inhibitors*
chemical_list: D056831:Coordination Complexes; D016166:Free Radical Scavengers; D008024:Ligands; D013481:Superoxides; D007811:Lanthanum; D003300:Copper; D000535:Aluminum