Antioxidative activities of a reductant in the ultrafiltrate of human placental homogenate.

ABSTRACT

From the ultrafiltrate of human term placental homogenate, a reductant possessing an absorption maximum at 345 nm but not around 260 nm was isolated through the process of Sephadex G-25 gel filtration and DEAE-Sepharose column chromatography. This substance bore resemblance to a reduced nicotinate moiety of nicotinamide nucleotide in regard to a decay in 345 nm absorption and 457 nm fluorescence maximum on oxidation and to an irreversible shift of absorption maximum from 345 nm to 300 nm on acidification. Unlike ascorbate, its ferricytochrome c-reduction was not superoxide-dependent. It scavenged hydroxyl radical produced by Fenton reaction. It did not promote the iron-catalyzed lipid peroxidation of intact and heat-inactivated rat liver microsomes but it inhibited the NADPH or ascorbate-mediated microsomal lipid peroxidation. In the placenta, containing high concentrations of ascorbate and iron ion, 345 nm substance was understood as an antioxidative reductant.