Free radical scavenging properties of guaiacol oligomers: a combined experimental and quantum study of the guaiacyl-moiety role.
Natural polyphenols are known to exhibit a lot of different biological properties, including antioxidant activity. For some polyphenols these activities are attributed to the presence of a guaiacol moiety. In the present paper we focus on the role of this moiety. For this purpose nine different compounds were enzymatically synthesized from guaiacol. To elucidate the structure-activity relationship of these polyphenols, DFT-(PCM)B3P86/6-311+G(2d,3pd)//(PCM)B3P86/6-31+G(d,p) calculations supported the experimental DPPH free radical scavenging activities. The antioxidant activities were correlated to (i) O-H BDEs (bond dissociation enthalpies), (ii) BDE(D) (BDE of a second H atom abstraction from the phenoxyradicals), (iii) spin density, (iv) HOMO (highest occupied molecular orbital) distribution, (v) IPs (ionization potentials), (vi) DeltaG and DeltaG(#) free energies of HAT (H atom transfer), and (vii) HAT rate constants. BDE(D) appeared to be the most important descriptor to understand the free radical scavenging ability of these compounds.
Anouar
E
E
Université de Limoges, EA 4021, Faculté de Pharmacie, 2 rue du Docteur Marcland, 87025 Limoges, France.
Calliste
C A
CA
Kosinová
P
P
Di Meo
F
F
Duroux
J L
JL
Champavier
Y
Y
Marakchi
K
K
Trouillas
P
P
D001713:Biphenyl Compounds / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004798:Enzymes / Q000378:metabolism; D016166:Free Radical Scavengers / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D006139:Guaiacol / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D010545:Peroxides / Q000737:chemistry; D010851:Picrates / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
D001713:Biphenyl Compounds; D004798:Enzymes; D016166:Free Radical Scavengers; D010545:Peroxides; D010851:Picrates; D011108:Polymers; C049375:perhydroxyl radical; D017665:Hydroxyl Radical; D006139:Guaiacol; C004931:1,1-diphenyl-2-picrylhydrazyl