In this work, a study about the consequences of the interaction among phenol compounds on antioxidant capacity is proposed. The antiradical activity evolution of an ethanol solution containing a mixture of three monophenols (catechin, resveratrol, and quercetin) was compared with the trend followed by each single phenol at three different temperatures (22, 37, and 60 degrees C). An initial increase and a following decrease in antioxidant activity were observed for all solutions at the three temperatures. The lower antiradical activity values of the mixture in comparison to the controls during the entire period of storage clearly showed that interaction among these polyphenols promotes a negative synergistic effect on this property.