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Aim The antioxidative and antinitrative activities of (1→3)-β- d -glucan (1–4 μg/ml) from the yeast cell walls of Saccharomyces cerevisiae in human plasma treated with strong oxidants – peroxynitrite (ONOO − ) (0.1 mM) and hydrogen peroxide (H 2 O 2 ) (2 mM) were studied in vitro. The main purpose of this study was to assess if (1→3)-β- d -glucan, a well known strong immunostimulatory agent, possesses a protective function against dual mechanism of ONOO − stroke associated with nitrative and oxidative damages to human plasma biomolecules. Scope The protein changes were determined in vitro by estimating the level of oxidative stress markers – carbonyl groups, and nitrative products – 3-nitrotyrosine residues. The plasma lipid peroxidation was also investigated. The obtained results show that (1→3)-β- d -glucan inhibits in vitro ONOO − -induced oxidation and nitration of plasma proteins, even by 50% and 30%, respectively. The antioxidative activity of (1→3)-β- d -glucan was confirmed by its inhibitory effect on plasma lipids peroxidation induced by ONOO − or by H 2 O 2 . Conclusions The obtained results demonstrate that (1→3)-β- d -glucan from S. cerevisiae protects plasma components against toxic effects of ONOO − and H 2 O 2 due to its antioxidative and antinitrative activities. Therefore (1→3)-β- d -glucan supplementation during inflammatory may be beneficial not only regard for its ability to stimulate the immune system but also by antioxidative properties.

Lots of plants belonging to Asteraceae family are very popular in folk medicine in Poland. These plants are also known as being rich in acidic polysaccharides, due to the presence of hexuronic acids or its derivatives. Our preliminary experiments have shown that the extract from Conyza canadensis L. possesses various biological activity, including antiplatelet, antiocoagulant and antioxidant properties. The aim of our study was to assess if macromolecular glycoconjugates from selected herbal plants of Asteraceae family: Achillea millefolium L., Arnica montana L., Echinacea purpurea L., Solidago virgaurea L., Chamomilla recutita (L.) Rauschert., and Conyza canadensis L. protect platelet proteins against nitrative and oxidative damage induced by peroxynitrite, which is responsible for oxidative/nitrative modifications of platelet proteins: the formation of 3-nitrotyrosine and carbonyl groups. These modifications may lead to changes of blood platelet functions and can have pathological consequences. The role of these different medicinal plants in the defence against oxidative/nitrative stress in human platelets is still unknown, therefore the oxidative damage to platelet proteins induced by peroxynitrite and protectory effects of tested conjugates by the estimation of carbonyl group level and nitrotyrosine formation (a marker of protein nitration) were studied in vitro. The antioxidative properties of the polyphenolic-polysaccharide conjugates from selected tested medicinal plants were also compared with the action of a well characterized antioxidative commercial polyphenol - resveratrol (3,4',5-trihydroxystilbene). The obtained results demonstrate that the compounds from herbal plants: A. millefolium, A. montana, E. purpurea, C. recutita, S. virgaurea, possess antioxidative properties and protect platelet proteins against peroxynitrite toxicity in vitro, similar to the glycoconjugates from C. canadensis. However, in the comparative studies, the polyphenolic-polysaccharide conjugates from selected tested medicinal plants were not found to be more effective antioxidant, than the solution of pure resveratrol.