Antioxidant and structure–activity relationships (SARs) of some phenolic and anilines compounds

The scavenging behavior of a series of phenolic and anilines compounds toward H2O2 and DPPH was examined. The efficient concentration (EC50) was calculated for all compounds under investigation by using H2O2-scavenging activity assay. The antiradical efficiency (AE) and EC50 were calculated for all investigated compounds by applying DPPH scavenging activity assay. Wide differences among compounds in each series and between the two series were observed. In H2O2-scavenging activity assay, the anilines series were more active than the phenolic series due to the reduction properties of the anilines compounds. While in the DPPH scavenging activity, the phenolic compounds were more active than the anilines compounds due to the lower bond dissociation energies (BDE) of O–H than that of N–H. So, the phenolic compounds were comparatively easier to lose H atom than anilines. The antioxidant activity related to the compound structure was found to be dependable on the number of the included active group (OH or NH2). The more active compound is the more included active groups. The position of the active groups also plays an important role of structure–antioxidant relationship activity. The ortho position was found to be the more active one, due to its ability to form intramolecular hydrogen bonding (iHB), followed by para position and then meta position of compounds.