6-7-dihydroxyflavone and 1-1-diphenyl-2-picrylhydrazyl

Topics: Animals; Antioxidants; Benzothiazoles; Biphenyl Compounds; Cadmium; Carbamates; Embryo, Nonmammalian; Eye Abnormalities; Flavones; Hydrogen Peroxide; Picrates; Sulfonic Acids; Tail; Yolk Sac; Zebrafish

The present study aims to establish the relationship between the reported radical-scavenging activities of flavonoids and some enthalpy changes that may occur during flavonoids' reactions with free radicals.. Eight flavonoids were chosen for the study on the basis of their structural merits and reported 1,1-diphenyl-2-picryl-hydrazyl scavenging activities. Enthalpy changes accompanying interconversions between selected conformations (including spin multiplicities) and homolytic dissociations were estimated.. A novel relationship exists between the total enthalpy of reaction for the abstraction of two hydrogen atoms from flavonoids, their reported radical-scavenging activities and the enthalpy of the homolytic dissociation of hydrogen molecule (104.206 kcal mol(-1)). Only those flavonoids which could give up two hydrogen atoms with total enthalpy changes well below 104.206 kcal mol(-1) were active radical scavengers.. By appealing to equilibrium dynamics, we demonstrated that, for flavonoids to be able to donate hydrogen atoms, the change in enthalpy accompanying the abstraction of two hydrogen atoms needs to be less than 104.206 kcal mol(-1). This condition does not seem to be restricted to flavonoids only but rather generally applicable to chian-breaking antioxidants.. Thermodynamical relationships may be the most important factors governing the radical-scavenging reactions of flavonoids and possibly other compounds as well. Nevertheless, a more complete characterization of antioxidants would necessitate kinetic analysis.

Topics: Biphenyl Compounds; Computational Biology; Flavones; Flavonoids; Free Radical Scavengers; Hydrogen; Hydrogen Bonding; Molecular Conformation; Picrates; Thermodynamics

We elucidated the protective effect of 7,8-dihydroxyflavone against hydrogen peroxide (H(2)O(2))-induced DNA damage. We found that 7,8-dihydroxyflavone scavenges 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and intracellular reactive oxygen species (ROS). 7,8-Dihydroxyflavone with antioxidant effect prevented the H(2)O(2)-induced cellular DNA damage, as evidenced by comet tail, 8-hydroxy-2'-deoxyguanosine (8-OHdG) content, and phospho-histone H2A.X protein expression. Hence, 7,8-dihydroxyflavone was shown to protect cell via the inhibition of apoptosis induced by H(2)O(2). This was substantiated by decreased apoptotic nuclear fragmentation, decreased sub-G(1) cell population, and decreased DNA fragmentation. Furthermore, 7,8-dihydroxyflavone activated the protein kinase B (PKB, Akt) signal pathway, which is a major survival signal pathway. In addition, LY294002, which is phosphatidylinositol 3 kinase (PI3K, upstream of Akt) inhibitor, attenuated the protective effect of 7,8-dihydroxyflavone against H(2)O(2)-induced cell damage. In conclusion, 7,8-dihydroxyflavone was shown to possess cytoprotective properties against oxidative stress by scavenging intracellular ROS and enhancing Akt activity.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Biphenyl Compounds; Blotting, Western; Cell Death; Cell Line; Comet Assay; Cricetinae; Deoxyguanosine; DNA Damage; DNA Fragmentation; Fibroblasts; Flavones; Free Radical Scavengers; Hydrogen Peroxide; Immunohistochemistry; Indicators and Reagents; Mutagens; Oncogene Protein v-akt; Oxidative Stress; Picrates; Reactive Oxygen Species; Signal Transduction