title: Unexpected role of 5-OH in DPPH radical-scavenging activity of 4-thiaflavans. Revealed by theoretical calculations.
abstract: The O-H bond dissociation enthalpies (BDEs) of 4-thiaflavans were calculated by a combined density functional theory method (RO)B3LYP/6-311 + G(2d,2p)//AM1/AM1. The calculated BDEs not only gave a reasonable explanation on the DPPH radical-scavenging activity difference of 4-thiaflavans, but also revealed the unexpected role of 5-OH in enhancing the antioxidant activity of A-ring.
authors.affiliation: Laboratory for Computational Biology and Shandong Provincial Research Center for Bioinformatic Engineering and Technique, Shandong University of Technology, Zibo 255049, PR China.
authors.forename: Lan-Fen
authors.initials: LF
authors.lastname: Wang
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Zhang
mesh_terms: D000975:Antioxidants / Q000737:chemistry; D001713:Biphenyl Compounds; D005419:Flavonoids / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D008962:Models, Theoretical; D010851:Picrates / Q000737:chemistry; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D005419:Flavonoids; D016166:Free Radical Scavengers; D010851:Picrates; D017665:Hydroxyl Radical; C004931:1,1-diphenyl-2-picrylhydrazyl