Growing evidence suggests that RNOS (reactive nitrogen and oxygen species) are involved in the damage of biomolecules, contributing to the aetiology of several human diseases. Thus, the demand for antioxidants has stimulated the search for new compounds with potential use in this field. The in vitro antioxidant potential of prenylated hydroquinones and prenylated 4-hydroxy-benzoic acids from fruits of P. crassinervium was evaluated in terms of their capacity to suppress both DPPH (2,2-diphenyl-1-picrylhydrazyl) radical and chemiluminescence produced from luminol, using 2,2'-azo-bis(2-amidinopropane) (ABAP) as a peroxyl radical source. The inhibition of lipid peroxidation was assessed using liposomes from phosphatidylcholine as a membrane model. The prenylated hydroquinones had higher antioxidant activity than the benzoic acids and, among the hydroquinones, the E isomer was more efficient than the Z isomer.