Antioxidant activity of alpha-pyridoin and its derivatives: possible mechanism.
alpha-Pyridoin (1, 1,2-di(2-pyridyl)-1,2-ethenediol) is a unique enediol antioxidant. To explore the detailed antioxidant mechanism of alpha-pyridoin, we synthesized alpha-pyridoin and its 5,5'- or 6,6'-bis-substituted derivatives (2-7) and compared their capacities to scavenge galvinoxyl radical (GO*) and protect human red blood cells (RBCs) from oxidative haemolysis. It was found that the compounds (5 and 6) with a methyl or methoxy group at the 5-position exhibit significantly higher GO*-scavenging and anti-haemolysis activities than other derivatives and vitamin C. Kinetic analysis of the GO*-scavenging reaction and the effect of added base on the reaction rate revealed that in ethyl acetate, the reaction occurs primarily by the direct hydrogen atom transfer (HAT mechanism). However, in ethanol that supports ionization, the kinetics of the process is mostly governed by sequential proton loss electron transfer (SPLET mechanism).
Cheng
Li-Xia
LX
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China.
Jin
Xiao-Ling
XL
Teng
Qing-Feng
QF
Chang
Jin
J
Yao
Xiao-Jun
XJ
Dai
Fang
F
Qian
Yi-Ping
YP
Tang
Jiang-Jiang
JJ
Li
Xiu-Zhuang
XZ
Zhou
Bo
B
D000975:Antioxidants / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D001559:Benzhydryl Compounds / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D010084:Oxidation-Reduction; D011725:Pyridines / Q000138:chemical synthesis / Q000494:pharmacology*; D013329:Structure-Activity Relationship
C532526:2,2'-pyridoin; D000975:Antioxidants; D001559:Benzhydryl Compounds; D011725:Pyridines; C020338:galvinoxyl