title: Probing into the Molecular Requirements for Antioxidant Activity in Plant Phenolic Compounds Utilizing a Combined Strategy of PCA and ANN.
abstract: OBJECTIVE
  This study investigates molecular structural requirements that are responsible for the antioxidant activity in phenolic compounds.
  
  
  METHODS
  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 polyphenolic acids.
  
  
  CONCLUSIONS
  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 antioxidant activity.
authors.affiliation: School of Pharmacy and Applied Science, La Trobe Institute for Molecular Sciences, La Trobe University, Edwards Rd, Bendigo 3550. Australia.
authors.forename: Snezana
authors.initials: S
authors.lastname: Agatonovic-Kustrin
authors.affiliation: School of Pharmacy and Applied Science, La Trobe Institute for Molecular Sciences, La Trobe University, Edwards Rd, Bendigo 3550. Australia.
authors.forename: David W
authors.initials: DW
authors.lastname: Morton
authors.affiliation: Innovation Centre of the Faculty of Chemistry Ltd., Studentski trg 12-16, 11000 Belgrade. Serbia.
authors.forename: Petar
authors.initials: P
authors.lastname: Ristivojevic
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology*; D001713:Biphenyl Compounds / Q000737:chemistry; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology; D062385:Hydroxybenzoates / Q000737:chemistry / Q000494:pharmacology; D016571:Neural Networks, Computer; D010636:Phenols / Q000737:chemistry* / Q000494:pharmacology*; D010851:Picrates / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry* / Q000494:pharmacology*; D010944:Plants / Q000737:chemistry; D025341:Principal Component Analysis; D021281:Quantitative Structure-Activity Relationship
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D005419:Flavonoids; D062385:Hydroxybenzoates; D010636:Phenols; D010851:Picrates; D010936:Plant Extracts; C004931:1,1-diphenyl-2-picrylhydrazyl; C017616:phenolic acid
keywords: Artificial neural networks; flavonoids; free radical scavenging; metal chelation; molecular descriptors; polyphenolic
  acids; principle component analysis