This study investigates the antioxidant capacity of 169 phenols using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, a widely used and inexpensive method. The authors standardized the experimental conditions and analyzed the correlation between the structures and activity of the phenols. The study is the first to investigate the largest number of components in terms of their Trolox equivalent antioxidant capacities (TEAC) under the same conditions. The results show that the ionization potential (IP) is the most important indicator for determining the presence or absence of activity in the DPPH assay. The study also compares the DPPH assay results with those from the hydrophilic-oxygen radical absorbance capacity (H-ORAC) method and analyzes the distribution of IP values for compounds in FooDB, a large food chemical database. The findings provide insights into the structure-activity relationships (SARs) of phenolic compounds and their antioxidant properties, which can be useful for creating new benchmarks and in silico tools for molecular design.This study investigates the antioxidant capacity of 169 phenols using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, a widely used and inexpensive method. The authors standardized the experimental conditions and analyzed the correlation between the structures and activity of the phenols. The study is the first to investigate the largest number of components in terms of their Trolox equivalent antioxidant capacities (TEAC) under the same conditions. The results show that the ionization potential (IP) is the most important indicator for determining the presence or absence of activity in the DPPH assay. The study also compares the DPPH assay results with those from the hydrophilic-oxygen radical absorbance capacity (H-ORAC) method and analyzes the distribution of IP values for compounds in FooDB, a large food chemical database. The findings provide insights into the structure-activity relationships (SARs) of phenolic compounds and their antioxidant properties, which can be useful for creating new benchmarks and in silico tools for molecular design.