Chemiluminescent methods showed that human lactoferrin more effectively inhibits free radical processes in the Fenton reaction than histidine and mannitol, usual tree radical scavengers. Human lactoferrin added to yolk lipoprotein suspension in the presence of rhodamine 6G reduces the intensity of fast flash of FeZ+-induced chemiluminescence by 37%. Complete saturation of lactoferrin with iron reduces its antioxidant properties by 15.4%, the intensity of chemiluminescence being below the control by 25.7%.Key Words: lactoferrin; apolactoferrin; hydrogen peroxide; chemiluminescence; .free-radical reactions Lactoferrin (LF), an important milk constituent, is involved in metabolic reactions, participates in the regulation of cell proliferation and immune response, and possesses important nutritional and antibacterial properties [4,5,9]. The role of LF in the mechanisms of antioxidant protection of breast milk remains poorly understood.Redox reactions in the organism are an essential part of metabolic processes and contribute to energy supply and transport and utilization of O 2 in tissues. Apart from oxidative phosphorylation utilizing 90% O 2, reactions generating active oxygen metabolites always occur in the organism. Apart from tetravalent reduction of O 2 in the redox reactions, its mono-, diand trivalent reduction occurs, in which reactive oxygen forms (O~, H20 ~, OH', and ~O 2) with high destructive potential are generated [2].The generation of these radicals is most effectively induced by metals with alternating valency, particularly F 2 § [3]. Abundant hemin and non-hemin iron compounds are potential centers of radical formation [4,5,9]. LF binds free Fe, which initiates and catalyzes free-radical processes, in particular lipid peroxidation (LPO) in biomembranes [4,5,[8][9][10].Department of Biochemistry and Microbiology, Rostov State University; Institute of Microbiology, Epidemiology, and Hygiene, Rostov-on-DonThe aim of the present study was Io investigate the effect of LF and the degree of its saturalion with iron on the intensity of free radical processes. MATERIALS AND METHODSThe following chemicals and reagents were used: chromatographic carriers Servacell CN-52 (Reanal) and Toyopearl HW-52 (Toyo-Soda); SDS (Serva); commercial LF and apoLF from human milk (Sigma); fluorescent dye Rhodamine 6G, histidine, and mannitol (Reanal); other reagents were of exlrapure grade.LF was isolated from colostrum (obtained during the first 4 days of lactation; fresh or stored at -20~ LF was isolated and purified by ion-exchange chromatography on Servacel CM-52 or gel fillration on Toyopearl HW-52 columns [71.LF was saturated with iron in a buffer containing 0.1 M sodium citrate and 0.1 M NaHCO~ (pH 8.5, buffer A); 1.2 ml 1.1% LF was titered by adding 20 pl of a solution containing 20 mM Fe 3+ in buffer A and spectrophotometrically measuring optical density at 470 nm. The content of LF-bound iron was deter|ni-ned by the phenanthroline method (sel~m iron assay) 11[. Chemiluminescent (CL) analysis of reactive oxygen specie...