Redox reactions of tocopherol monoglucoside in aqueous solutions: a pulse radiolysis study.
The reactions between tocopherol monoglucoside (TMG), a water-soluble vitamin-E derivative, with Br2.-, N3., (SCN)2.-, NO2., OH. and various halogenated peroxyl radicals were examined using a pulse radiolysis technique. The results demonstrate that TMG forms a stable phenoxyl radical at pH > 6.8. The thus-formed phenoxyl radical shows pH-dependent decay kinetics and is disproportionated by 2nd order kinetics at pH 2.3. It was observed that the TMG reactivity towards a halogenated peroxyl radical increases with the number of halogen atoms at the carbon atom having a peroxyl group. The reaction between the TMG phenoxyl radical and ascorbic acid was also examined using a pulse radiolysis technique. The results indicate that the TMG phenoxyl radical is repaired by ascorbate. Kinetic studies indicate that TMG may act as an antioxidant to repair free-radical damage to some biologically important compounds. The one-electron reduction potential for TMG was found to be 0.522 V +/- 0.06 vs. NHE.
Kapoor
Sudhir
S
Radiation Chemistry & Chemical Dynamics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India. sudhirk@apsara.barc.ernet.in
Mukherjee
Tulsi
T
Kagiya
Tsutomu V
TV
Nair
Cherupally Krishnan K
CK
D001205:Ascorbic Acid / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D005960:Glucosides / Q000737:chemistry* / Q000528:radiation effects*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry; D011675:Pulse Radiolysis; D012996:Solutions; D024505:Tocopherols / Q000031:analogs & derivatives / Q000737:chemistry* / Q000528:radiation effects*; D014867:Water
D005609:Free Radicals; D005960:Glucosides; D010545:Peroxides; D012996:Solutions; C460320:tocopherol monoglucoside; D014867:Water; C049375:perhydroxyl radical; D001205:Ascorbic Acid; D024505:Tocopherols