Protective effect of Castanea sativa and Quercus robur leaf extracts against oxygen and nitrogen reactive species

Topical natural antioxidants are a useful strategy for the prevention of photoaging and oxidative stress mediated skin diseases. In view of this underlying principle, the screening of natural plant extracts with scavenging activity for pro-oxidant reactive species is a primary requirement for the development of new topical antioxidant formulations. In the present study, an ethanol:water (7:3) extract from Castanea sativa leaves and a ethanol:water (2:3) extract from Quercus robur leaves were evaluated for their putative in vitro   scavenging effects on reactive oxygen species (ROS) namely superoxide radical (O2-), hydroxyl radical (HO), peroxyl radical (ROO), hydrogen peroxide (H2O2) and singlet oxygen (1O2) as well as on reactive nitrogen species (RNS) namely nitric oxide (NO) and peroxynitrite (ONOO−).The extracts presented a high potency to scavenge the tested reactive species, all the IC50s being found at the μg/mL level. IC50s (mean ± SE) for the ROS O2-,HO,H2O2 and 1O2 were 13.6 ± 1.8; 216 ± 4; 410 ± 8; 12.3 ± 0.7 μg/mL, respectively, for C. sativa, and 11.0 ± 0.5; 285 ± 22; 251 ± 32; 7.90 ± 0.56 μg/mL, respectively, for Q. robur. The ORAC values obtained for ROO were 1.24 ± 0.13 for C. sativa and 1.09 ± 0.06 for Q. robur.The IC50s (mean ± SE) for NO and ONOO− were 3.10 ± 0.14 and 1.49 ± 0.10 μg/mL, respectively, for C. sativa and 3.13 ± 0.11 and 0.95 ± 0.02 μg/mL, respectively, for Q. robur. The content of total phenolics for C. sativa and Q. robur were 284 ± 9 and 346 ± 4 mg of gallic acid equivalents (GAE)/g of lyophilized extract respectively. The observed effects might be of relevance considering the putative interest of these extracts as topical antioxidants.