Phenolics are among the most abundant organics in nature but their biological activities remain poorly understood. Traditional approaches to characterize materials starts with structure determination yet this approach has been less successful for phenolics because of their structural complexity and heterogeneity. Here an electrochemical reverse engineering approach that focuses on materials properties (vs structure) was used to infer function. We studied three phenolics that are abundant in food: the small molecule chlorogenic acid, the macromolecule proanthocyanidins, and the insoluble tannin from persimmon. We observed that all three phenolics are redox active and can repeatedly donate and accept electrons. Further, we provide evidence that all three kinds of phenolics can undergo redox-cycling with the analgesic acetaminophen. These results suggest that the reversible redox properties of phenolics may confer important biological activities even under conditions that would suggest they are unavailable biologically because their size would restrict absorption into the bloodstream or even dissolution. (C) 2018 Published by Elsevier Ltd.