The novel electrochemical approach based on coulometric response of electro-generated superoxide is applied to the radical scavenging activity determination of hydroxy substituted tetraphenylporphyrins. The excellent linearity of the coulometric response of superoxide ion vs. porphyrins concentration for the wide concentration range shows the operational suitability of developed approaches. The most feasible mechanism of antioxidant activity of hydroxy substituted tetraphenylporphyrins is confirmed using analysis of correlations between the electrochemical behavior of porphyrins and their radical scavenging properties. (C) 2016 Elsevier B.V. All rights reserved.