Abstract We take a wide variety of antioxidants, including polyphenols, daily from our diet. They are generally considered to be beneficial for our health. However, the intrinsic function of antioxidants in biological systems remain unknown. On the other hand, antioxidants in general are sensitive to oxidation, generating their oxidized intermediates. Intriguingly, these intermediates are highly reactive to proteins. Although the specific cellular targets and response mechanism remain unclear, protein modification by oxidized antioxidants may represent the intrinsic “moonlight” function of antioxidants by taking on a secondary role beyond their traditional activity. This minireview summarizes recent findings on antioxidants, with a particular focus on the interactions of antioxidant-modified proteins with histones.