Aim and Objective: This study investigates molecular structural requirements that are
responsible for the antioxidant activity in phenolic compounds.
Method: Antioxidant activity of compounds was determined with a 2,2-diphenyl-1-picrylhydrazyl
(DPPH) free radical assay. Principal component analysis (PCA) was used to classify phenolic
antioxidants according to the key molecular features that contribute to their antioxidant activity.
Artificial neutral networks (ANNs) was used to develop a predictive QSAR model.
Results: Both models agreed that structural characteristics of phenolic compounds responsible for the
antioxidant activity include: (1) number and position of alcohol groups on the aromatic ring; (2)
molecular size; (3) flexibility/bulkiness; and (4) water solubility. PCA has classified data into phenolic
acids and flavonoids, suggesting two distinct mechanisms of action. ANN has confirmed different
mechanisms of action for flavonoids and polyphenolic acids, i.e. breaking of free radical chain
reactions by donation of a hydrogen atom to neutralise a free radical and the chelating ability of
Conclusion: Although two phenolic acids may have the same relative polarity, their different
functional groups may drastically change the nature of their interactions with free radicals, and their