59 Biomedical and Biopharmaceutical Research J o r n a l d e I n v e s t i g a ç ã o B i o m é d i c a e B i o f a r m a c ê u t i c aIn vitro antioxidant properties of the diterpenes Parvifloron D and 7α-acetoxy-6β-hydroxyroyleanone AbstractThe involvement of oxidative stress in several pathological and toxicological phenomena supports the quest for novel antioxidants. Plants from the Plectranthus genus contain bioactive components, including antioxidant compounds. In this work, the antioxidant activity of two diterpene compounds extracted from Plectranthus plants, Parvifloron D (ParvD) and 7α-acetoxy-6β-hydroxyroyleanone (Roy) was evaluated. First, the DPPH assay was used to assess the reducing capacity of these compounds. ParvD was shown to have a much stronger antioxidant activity than Roy and was therefore selected for further studies. The ability of ParvD to degrade H 2 O 2 was evaluated, but no activity was found. To assess if ParvD is able to protect DNA from ROS-induced DNA breaks, a plasmid cleavage assay was conducted. Treatment with H2O2 + Fe(II) altered the plasmid DNA conformation. In contrast, plasmid DNA treated with ParvD + H 2 O 2 + Fe(II) retained its supercoiled conformation, suggesting that ParvD protects DNA from oxidative breakage. These findings support that ParvD has antioxidant activity. Further work is planned to assess the antioxidant and DNA protective effects in cell based assays in order to validate the results found in these in vitro tests.