Nitric oxide (·NO)-derived reactive species react rapidly with oxidizable unsaturated fatty acids to yield nitrated products. Arachidonic acid (AA, 20:4) is a polyunsaturated fatty acid present in biological membranes, being precursor of many bioactive and signaling molecules (i.e prostaglandins). The aim of this work was to determine the biological activity of nitrated arachidonic acid obtained by different synthesis pathways, focusing on their ability to release ·NO, induce vasorelaxation and affect platelet aggregation. Synthesis of methyl-nitroarachidonate (MNA) and nitroarachidonic acid (NA) was performed by incubation reactions of methyl-arachidonate or arachidonic acid, respectively, with NaNO₂ in acidic medium and products were characterized by NMR, IR and MS. ·NO release was determined by oxyhemoglobin oxidation and EPR using carboxyPTIO as a spin trap. Vasorelaxation was performed in aortic rings (4 mm thickness) obtained from anesthetized rats. The developed tension was recorded with an isometric tension transducer. Rings were precontracted with 1mM norepinephrine in the presence or absence of endothelium. After plateau, 10 mM MNA or NA were added to evaluate vasorelaxation. For platelet aggregation studies, platelet-rich plasma of healthy volunteers was treated with 20 mM MNA and aggregation was recorded by spectrophotometry under stirring (l = 700 nm). While NA was able to release ·NO in aqueous solution exhibiting parallel vasorelaxing properties, MNA was not a ·NO donor in the same experimental conditions, producing vasorelaxation in a mechanism that did not involve ·NO release. NA or MNA-mediated vasorelaxation was not statistically different when compared in the presence or absence of endothelium. Moreover, vasorelaxation was inhibited by 30mM ODQ (a well-know guanylate cyclase inhibitor), suggesting the involvement of cGMP. On the other hand, MNA induced platelet aggregation in lower extent than arachidonic acid. These results reveal that synthetic nitroarachidonates have the ability to induce endothelium-independent vasorelaxation via guanylate cyclase activation, exhibiting other anti-inflammatory properties, i.e reduction of the trombogenic capacity of arachidonic acid. Therefore, these products could be generated in vivo as a compensatory mechanism against lipid oxidation processes.