Simply put, a free radical scavenger is a molecule that reacts with a high energy free radical species (like the lipid peroxide radical formed in step 2 of the figure above) in a radical chain propaga...Simply put, a free radical scavenger is a molecule that reacts with a high energy free radical species (like the lipid peroxide radical formed in step 2 of the figure above) in a radical chain propagation step, forming a more stable radical species which can be metabolized in some way before further damage is done to cell constituents.