Essential oils (EO) of Piper auritum ("hoja santa") and Porophyllum ruderale ("papalo" or "papalo quelite"), previously dried, were obtained by supercritical extraction (SCE) with CO2. Oil extraction was performed at two temperatures (40 and 50 degrees C) and two pressures (10.34 and 17.24 MPa). The steam distillation (SDE) method was used also for extraction of EO. Oils were analyzed in antioxidant activity (ABTS method). The chemical composition of oils, by gas chromatography mass spectroscopy (GC-MS). Piper auritum oil yields were in the range 2.37 +/- 0.05-3.09 +/- 0.12 g oil/100 g dry material and in Porophyllum ruderale the yields were 0.82 +/- 0.01-1.35 +/- 0.09 g oil/100 g dry material. The antioxidant activity, for plants, were in the range 1.30-11.65 mg equivalent of Trolox/g of oil and 1.09-10.16 mg of ascorbic acid equivalent/g of oil. The main components identified by GC MS in Piper auritum oil were safrole and phytol and in Porophyllum ruderale oil were isosafrole, cc-copaene and phytol.