Pulse radiolytic oxidation of beta-carotene with halogenated alkylperoxyl radicals in a quaternary microemulsion: formation of retinol.
Pulse radiolytically generated halogenated alkylperoxyl radicals, namely CCl3OO*, CBr3OO*, CHCl2OO*, CHBr2OO*, etc. have been employed for a study of the oxidation of beta-carotene in a quaternary microemulsion. All these halogenated alkylperoxyl radicals produce a radical cation (absorption maximum at 840 nm), either via the initial formation of an adduct (absorption maximum at 740 nm), or by direct reaction. There was a considerable blue shift of both absorption peaks in the present system as compared to those earlier reported in non-polar as well as in micellar media. An additional intense absorption peak at approximately 345 nm was noted at a longer time scale and was stable up to 5 ms. On irradiation with a large number of electron pulses, a stable product with an absorption maximum at 315 nm appeared. On excitation at 315 nm, this product gave a fluorescence spectrum with an emission maximum at 525 nm. The absorption and fluorescence spectra of the stable product compared with those of retinol; this was further confirmed by HPLC analysis. A suitable mechanism has been proposed.
Adhikari
S
S
Radiation Chemistry & Chemical Dynamics Division, Bhabha Atomic Research Centre, Mumbai, India. asoumya@apsara.barc.ernet.in
Kapoor
S
S
Chattopadhyay
S
S
Mukherjee
T
T
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004655:Emulsions / Q000737:chemistry; D006219:Halogens / Q000737:chemistry*; D006801:Humans; D010084:Oxidation-Reduction; D011675:Pulse Radiolysis; D017382:Reactive Oxygen Species; D014801:Vitamin A / Q000737:chemistry*; D019207:beta Carotene / Q000737:chemistry*
D004655:Emulsions; D006219:Halogens; D017382:Reactive Oxygen Species; D019207:beta Carotene; D014801:Vitamin A