title: Scavenging effect of chinonin on free radicals studied with quantum chemistry.
abstract: OBJECTIVE
  To study whether the xanthonoid structure can enhance the ability of chinonin to scavenge free radicals and to understand the sequence of activity of chinonin hydroxyls.
  
  
  METHODS
  Semiempirical quantum chemistry method AM1 was employed to calculate delta HOF values, the differences between heat of formations of mother molecule and its free radicals, and spin density distribution of different states of chinonin. delta HOF values were used as theoretical indices to measure scavenging activity of chinonin on free radicals and effects of structure on delta HOF values were investigated.
  
  
  RESULTS
  delta HOF values of different phenolics were calculated to be 139.09 kJ.mol-1 (O5-H6), 141.46 kJ.mol-1 (O4-H5), 185.14 kJ.mol-1 (O2-H2) and 195.71 kJ.mol-1 (O1-H1). Spin density distribution of free radicals were obtained as well.
  
  
  CONCLUSIONS
  Xanthonoid structure of chinonin made ring C to display high passive effect on ring B, which reduced scavenging activity of phenolics of ring B on free radicals. The sequence of activities of chinonin hydroxyls was O5-H6 > O4-H5 > O2-H2 > O1-H1.
authors.affiliation: Department of Biology, Shandong Teachers' University, Ji-nan, China. zhysdtu@jn-public.sd.cninfo.net
authors.forename: H Y
authors.initials: HY
authors.lastname: Zhang
mesh_terms: D016166:Free Radical Scavengers / Q000737:chemistry* / Q000494:pharmacology; D006027:Glycosides / Q000737:chemistry* / Q000494:pharmacology; D015394:Molecular Structure; D011789:Quantum Theory; D013329:Structure-Activity Relationship; D014966:Xanthenes / Q000737:chemistry* / Q000494:pharmacology; D044004:Xanthones
chemical_list: D016166:Free Radical Scavengers; D006027:Glycosides; D014966:Xanthenes; D044004:Xanthones; C013592:mangiferin