Abstract
Schinus fasciculata and S. praecox (Anacardiaceae) can be found among the characteristic vegetation components of the phytogeographic province of the Espinal. The essential oils from these two species have been obtained from fresh material by hydrodistillation and analyzed by GC and GC-MS. We have compared the chemical composition of the oils obtained from samples collected at two different natural environments and at different phenological phases. The antioxidant activity of these oils was evaluated by the DPPH assay. S. fasciculata and S. praecox showed significant differences in their chemical composition as well as in their radical scavenger ability. The essential oil from samples of S. fasciculata attacked by plant-lice (Hemiptera, Psylloidea) was the more active one, with inhibition percentages higher than that of the reference compound.