Binding of Iron (II) Ions by Aqueous Extractions from Yerba Mate (Ilex paraguariensis).

We studied the ability of an aqueous extract from yerba mate and a dry extract obtained on the basis of this aqueous extract to remove Fe(II) ions from an aqueous medium. Aqueous extracts from mate dose-dependently reduced the concentration of free Fe(II) ions assayed by the reaction with 1,10-phenanthroline. This can be attributed to polyphenolic compounds with iron-chelating properties present in aqueous extracts from mate, namely quercetin, rutin, caffeic and chlorogenic acids. These substances effectively removed Fe(II) ions from the medium (the initial concentration of these ions was 15 µM) in the concentration range of 20-30 µM. Binding of Fe(II) ions by aqueous mate extracts (due to the formation of chelate complexes with the participation of polyphenolic compounds) modified their absorption spectra in the visible region. Binding of Fe(II) ions can be a mechanism of the antioxidant action of yerba mate.

The Effect of Dihydroquercetin on Catalytic Activity of Iron (II) Ions in the Fenton Reaction.

Dihydroquercetin is a natural flavonoid with antioxidant properties that are determined by its ability to scavenge free radicals and chelate transition metal ions. Chemiluminescent studies showed that iron (II) ions in complex with dihydroquercetin are inactive and cannot catalyze decomposition of hydrogen peroxide (Fenton reaction).

[Antioxidative activity of histochrome and some other drugs used in ophthalmology]. / Antioksidantnaia aktivnost' gistokhroma i nekotorykh lekarstvennykh preparatov, primeniaemykh v oftal'mologii.

The antioxidative activity (AOA) of histochrome (2,3,5,6,8-pentahydroxy-7-ethyl-1,4-naphthoquinone) and some other drugs with antioxidant properties used in ophthalmology has been studied in the hemoglobin--hydrogen peroxide--luminol system. The AOA of histochrome, ascorbate, dicinon, rutin, quercetin, and dihydroquercetin is comparable to that of trolox, the reference antioxidant in our studies. The drugs (in physiological concentrations) listed above are characterized by a high AOA. Cerebrolysin was 300 times less active than trolox, and emoxipin showed no antioxidant properties. Lacrimal AOA increased after a parabulbar injection of histochrome. Histochrome is believed to be a perspective antioxidant for the treatment of ocular diseases.

Effect of carnosine and its components on free-radical reactions.

The antioxidant properties of carnosine and its components histidine and beta-alanine were compared using several model systems: glutathione-horseradish peroxidase-luminol (GSH-HRP-luminol), xanthine-xanthine oxidase (X-XO), stimulated human blood polymorphonuclear leukocytes (PML), and egg yolk phospholipid liposomes in the presence of Fe2+ ions. Carnosine and histidine (30-40 mM) were shown to cause 50% suppression of free radical reactions in the GSH-HRP-luminol system, whereas beta-alanine displayed no activity. The O(2-)-scavenging activity of carnosine in the X-XO system was demonstrated; 50% inhibition was achieved at 7.1 x 10(-5) M. Suppression of the luminol-dependent PML chemiluminescence by carnosine and reduction of the latent period of the Fe(2+)-induced chemiluminescence of the liposome suspension was suggested to demonstrate its ability to interact with Ca2+ and Fe2+ ions. This was confirmed by the o-phenanthroline test. The results obtained demonstrate that carnosine is capable of scavenging different radicals and binding divalent metal ions. The antioxidant activity of carnosine was observed in all the systems studied, and carnosine effective concentrations corresponded to those found in the brain and muscles. The universal effects of carnosine and its high concentration in excitable tissues suggest this dipeptide to be an inhibitor of free radical reactions in vivo.