Walnut (Juglans regia) leaf extracts are strong scavengers of pro-oxidant reactive species

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 center dot), superoxide radical (O-2(center dot-)), peroxyl radical (ROO center dot) and hydrogen peroxide (H2O2)] and reactive nitrogen species (RNS) [nitric oxide ((NO)-N-center dot) and peroxynitrite anion (ONOO-)]. The extract presented a potent scavenging activity against all the reactive species tested, all the IC(50)s being found at the mu g/mL level. IC50S (mean SE) for the ROS O-2(center dot-) and H2O2 were 47.6 +/- 14.6, 383 +/- 17 mu g/mL, respectively. The oxygen radical absorbance capacity (ORAC) value obtained for ROO center dot was 2.17 +/- 0.22 mu mol Trolox equivalents/mg extract. The IC50S for (NO)-N-center dot and ONOO- were 1.95 +/- 0.29 and 1.66 +/- 0.10 mu g/mL, respectively. The content of total phenolics was 270 3 mg 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. (C) 2007 Elsevier Ltd. All rights reserved.