@misc{oai:repo.qst.go.jp:00075179,
 author = {Nakanishi, Ikuo and Ohkubo, Kei and Imai, Kohei and Ken-ichiro, Matsumoto and Ozawa, Toshihiko and Hamada, Hiroki and Fukuhara, Kiyoshi and Nakanishi, Ikuo and Ohkubo, Kei and Imai, Kohei and Matsumoto, Kenichiro and Ozawa, Toshihiko},
 month = {Apr},
 note = {Flavonols show an efficient scavenging activity against reactive oxygen radicals.  However, the detailed mechanism has yet to be fully clarified.  There are two mechanism for the radical-scavenging reactions of phenolic antioxidants, i.e., one-step hydrogen-atom transfer (HAT) and electron transfer followed by proton transfer (ET-PT).  In this study, we discuss the radical-scavenging mechanism for 6 flavonols, which are myricetin (Myr), quercetin (Que), kaempferol (Kae), and 3 methylated quercetin analogs (2’-MeQue, 5’-MeQue, and Me2Que), based on the relationships between the scavenging rate constants (k) against galvinoxyl radical and thermodynamic parameters, such as O-H bond dissociation energies (DHT) and ionization potentials (IP), calculated by the density functional theory (DFT).
The k values were determined in deaerated acetonitrile at 298 K by a stopped-flow technique.  DFT calculations were carried out at the B3LYP/6-31G(d) level.
The k value increases in the order: Que < 2’-MeQue ≈ Kae < Me2Que < Myr < 5’-MeQue.  The plot of the logarithm of the k values (log k) vs. DHT or IP values revealed that the log k values for 5’-MeQue, Myr, Me2Que, and Que are linearly correlated with their IP values.  These results suggest that the radical-scavenging reaction by these 4 flavonols may proceeds via the ET-PT mechanism., The 9th Biennial Meeting of Society for Free Radical Research-Asia (SFRR-Asia)},
 title = {Structure-Activity and Structure-Mechanism Relationships for the Radical-Scavenging Reaction of Flavonols},
 year = {2019}
}