Comparative study of antioxidant properties of immunoregulatory peptides.

We studied antioxidant properties of immunofan, bursin, cyclobursin, thymopoietin II fragment, glycine, and Siberian ginseng. Experiments were performed in 2 model systems: Fe(2+)-induced oxidation of multilamellar phospholipid liposomes in a heterogeneous water-lipid system and oxidation of luminol induced by alpha,alpha'-azo-bis(isobutyramidine dihydrochloride) in a homogenous aqueous system. By the ability to entrap lipid peroxyl radicals, antioxidant activity of substances decreased in the following order: Siberian ginseng extract>bursin>cyclobursin>thymopoietin II fragment>immunofan, glycine. Siberian ginseng extract and thymopoietin II fragment interacted with Fe(2+), which contributed to elimination of catalyst of lipid peroxidation from the system. The ability of substances to interact with aqueous peroxyl radicals and luminol radicals decreased in the following order: Siberian ginseng extract>thymopoietin II fragment>immunofan>glycine, cyclobursin, bursin. Substances with high antioxidant activity improved the state of the endogenous antioxidant system and protected cells from oxidative stress. They entrapped reactive oxygen species formed in the cytoplasm, modulated free radical processes, and regulated the synthesis of bioactive molecules.