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Abstract: The growing interest in the substitution of synthetic food antioxidants by natural ones has fostered research on vegetable sources and on the screening of raw materials, for identifying new antioxidants. In the present study, an ethanol:water (4:6) extract from Juglans regia leaves was evaluated for its putative in vitro scavenging effects on reactive oxygen species (ROS) [hydroxyl radical (HO ), superoxide radical , peroxyl radical (ROO ) and hydrogen peroxide (H2O2)] and reactive nitrogen species (RNS) [nitric oxide ( NO) and peroxynitrite anion (ONOO−)]. The extract presented a potent scavenging activity against all the reactive species tested, all the IC50s being found at the μg/mL level. IC50s (mean±SE) for the ROS and H2O2 were 47.6±4.6, 383±17μg/mL, respectively. The oxygen radical absorbance capacity (ORAC) value obtained for ROO was 2.17±0.22μmol Trolox equivalents/mg extract. The IC50s for NO and ONOO− were 1.95±0.29 and 1.66±0.10μg/mL, respectively. The content of total phenolics was 270±3mg of gallic acid equivalents (GAE)/g of lyophilised extract. These results showed that J. regia leaf extracts can be used as an easily accessible source of natural antioxidants. [Copyright &y& Elsevier]