title: Insight into the free-radical-scavenging mechanism of hydroxyl-substituent Schiff bases in the free-radical-induced hemolysis of erythrocytes.
abstract: This work aimed to explore the mechanism by which hydroxyl-substituent Schiff bases scavenge free-radicals. Thus, four Schiff bases, that is benzylidene aniline (BAN), 2-(phenyliminomethyl)phenol (BAH), 4-benzimidoylphenol (PBH) and 2-benzimidoylphenol (OBH), were applied to protect human erythrocytes against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced hemolysis. The results revealed that the --OH attached to the ortho-position of methylene in Schiff base scavenges 1.46 radicals per molecule, the --OH attached to the para-position of the N atom scavenges 2.94 radicals and the --OH attached to the ortho-position of the N atom scavenges 3.63 radicals. In addition, four Schiff bases were used together with some familiar antioxidants, such as 6-hydroxyl-2,5,7,8-tetramethyl chroman-2-carboxylic acid (Trolox), L-ascorbic acid (VC), alpha-tocopherol (TOH) and L-ascorbyl-6-laurate (VC-12) in AAPH-induced hemolysis of erythrocytes. It was found that, except for BAN+VC-12, BAH + VC-12, OBH + VC-12 and PBH+TOH, all the other combinations protected erythrocytes more perfectly than when used individually. This result demonstrated that a promotive protection existed between Schiff base and other antioxidants and this improved their ability to scavenge free-radicals. Finally, IC(50) values of the aforementioned Schiff bases together with 2-((o-hydroxylphenylimino) methyl)phenol (OSAP) and 2-((p-hydroxylphenylimino)methyl)phenol (PSAP) were determined by reaction with two radical species, that is, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTS(+.)) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH). The results implied that the molecular framework of a Schiff base and an --OH attached to the ortho-position of methylene were apt to reduce radicals, but the --OH attached to the aniline ring in a Schiff base was prone to scavenge radicals directly.
authors.affiliation: Department of Organic Chemistry, College of Chemistry, Jilin University, Changchun, China.
authors.forename: You-Zhi
authors.initials: YZ
authors.lastname: Tang
authors.forename: Zai-Qun
authors.initials: ZQ
authors.lastname: Liu
mesh_terms: D000578:Amidines / Q000737:chemistry / Q000494:pharmacology; D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology; D052160:Benzothiazoles / Q000737:chemistry / Q000494:pharmacology; D001713:Biphenyl Compounds; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects*; D016166:Free Radical Scavengers / Q000737:chemistry / Q000494:pharmacology*; D005609:Free Radicals / Q000737:chemistry / Q000494:pharmacology*; D006461:Hemolysis / Q000187:drug effects*; D006801:Humans; D015394:Molecular Structure; D010851:Picrates / Q000737:chemistry / Q000494:pharmacology; D012545:Schiff Bases / Q000737:chemistry / Q000494:pharmacology*; D013451:Sulfonic Acids / Q000737:chemistry / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000578:Amidines; D000975:Antioxidants; D052160:Benzothiazoles; D001713:Biphenyl Compounds; D016166:Free Radical Scavengers; D005609:Free Radicals; D010851:Picrates; D012545:Schiff Bases; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C046728:2,2'-azobis(2-amidinopropane); C004931:1,1-diphenyl-2-picrylhydrazyl