Peroxyl-radical-scavenging activity of garlic: 2-propenesulfenic acid versus allicin.
The OOH radical reactions with allicin and its Cope elimination products (2-propenesulfenic acid and thioacrolein) in aqueous solution have been studied. The CBS-QB3 quantum chemistry method has been used, with geometries and frequencies at BHandHLYP/6-311++G(d,p) level and conventional transition state theory. 2-Propenesulfenic acid is predicted to be over 1000 times more reactive toward OOH radical than allicin (2.60 x 10(7) vs 7.38 x 10(3) L mol(-1) s(-1), at 298 K). Accordingly, our results strongly support the novel suggestion by Vaidya et al. (Angew. Chem., Int. Ed. 2009, 48, 157) that the active ingredient responsible for the free radical scavenging activity of garlic is actually 2-propenesulfenic acid and not allicin. In addition, direct reaction branching ratios and product distribution for the three studied reactions are proposed for the first time.
Galano
Annia
A
Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, San Rafael Atlixco 186, Col. Vicentina C.P. 09340 Iztapalapa, México D.F., Mexico. agalano@prodigy.net.mx
Francisco-Marquez
Misaela
M
D004220:Disulfides; D016166:Free Radical Scavengers / Q000737:chemistry*; D005737:Garlic / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D010545:Peroxides / Q000737:chemistry*; D013434:Sulfenic Acids / Q000737:chemistry*; D013441:Sulfinic Acids / Q000737:chemistry*; D013816:Thermodynamics
C547385:2-propenesulfenic acid; D004220:Disulfides; D016166:Free Radical Scavengers; D010545:Peroxides; D013434:Sulfenic Acids; D013441:Sulfinic Acids; C049375:perhydroxyl radical; C006452:allicin