Abstract. The purpose of this study was to examine the effects of powder particle size on the cytoprotective and antioxidant activity of Hedera helix (HH) and Scrophularia nodosa (SN), two medicinal plants more commonly known as ivy and figwort, against H2O2-induced oxidative stress in mouse primary spleen cells. Thus, the preventive effects of powders of 3 different granulometric classes (50–100 μm, 100–180 μm and 180–315 μm) and those of the hydroethanolic (HE) extract from HH and SN on oxidative stress were compared by monitoring reactive oxygen species (ROS) formation, malondialdehyde (MDA) production, and the activity of enzymatic antioxidants including catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx). Results showed that pretreatment with the 3 fine powders from both plants generally offered to H2O2-exposed spleen cells, a protection against oxidative stress, highlighted by a significant decrease of both ROS formation and the level of MDA ( p < 0.001), and a significant increase of GPx activity ( p < 0.05). The two superfine powders (i.e. 50–100 μm and 100–180 μm), at 250 μg/mL, were more effective in modulating all oxidative stress markers studied than both HE extracts ( p < 0.01), and the powder with the highest particular size (i.e., 180–315 μm) ( p < 0.01). Compared to untreated cells, our results suggest that pretreatment with powders, in particular the superfine fractions, has relatively restored the levels of antioxidant-related enzymes including GPx, CAT and SOD. In summary, our results suggest differential effects between the 3 different fine powders studied, with the best cytoprotective and antioxidant activities being in favor of the superfine powders.
