Objective: To assess the effect of 4-hydroxy-3,5-di-tret-butyl cinnamic acid on the state of endothelial function under conditions of experimental cerebral ischemia. Materials and Methods: Antioxidant properties of 4-hydroxy-3,5-di-tret-butyl cinnamic acid and the effect of this compound on NO-synthase system activity and ADMA concentration were evaluated. Results: As a result, it has been found that the use of 4-hydroxy-3,5-di-tretbutyl cinnamic acid promotes reduction activity of catalase, glutathione peroxidase, superoxide dismutase and a decrease in the concentration of MDA and DC. In addition, the ability to modulate NO synthase system activity was established for this compound: an increase in eNOS activity by 114.2% (p <0.05), decrease activity of nNOS and iNOS by 60.6% (p <0.05) and 61.9% (p <0.05), respectively, decrease concentration of ADMA by 83.9% (p <0.05). Conclusion: The results of the conducted researches it is established that 4-hydroxy-3,5-di-tret-butyl cinnamic acid has antioxidant and NOS -regulating effect.Key words: Experimental ischemic stroke, Derivatives of cinnamic acid, Antioxidant, Endothelium, Endothelioprotection, Rats. This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.