In the present study, the bark ethanol extract of Maytenus guyanensis Klotzch (Celastraceae) was investigated for total phenol content, free radical scavenging (DPPH,ABTS, superoxide anion radical and singlet oxygen), antiinflammatory, antiplatelet and antiaggregating activities. M. guyanensis exhibited IC50 8.2 ± 0.2, 28.4 ± 0.7, 35.6 ± 3.0 and 517 ± 70.8 µg/mL in the DPPH, ABTS, superoxide and singlet oxygen assays, respectively. Total phenol content was found to be 58.7 ± 1.7 mEq gallic acid (mg/g dry extract). Significant antiinflammatory activity was demonstrated when extract was orally administrated (400 mg/kg b.w.) reducing edema in 40 % when compared with carrageenin. Also, exhibited antiplatelet aggregating activity, with IC50 142 ± 14.3, 133 ± 2.3 and 166 ± 0.3 µg/mL, for platelet aggregation, when induced by adrenalin, adenosine diphosphate or arachidonic acid, respectively. These results suggest that M. guyanensis bark extract could have potential applications in oxidative, inflammatory and homeostasis-related dysfunctions.Colegio de Farmacéuticos de la Provincia de Buenos Aire