Remarkable enhancement of antioxidant activity of vitamin C in an artificial bilayer by making it lipo-soluble.
The reaction kinetics between 4-palmitoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO-16) and vitamin C (VC) and its lipophilic derivative ascorbyl-6-palmitate (VC-16) was studied by stopped-flow ESR spectroscopy in a synthetic surfactant vesicle sodium 1-pentadecyl hexadecyl sulfate (SPHS). TEMPO-16 reacted with VC very slowly and showed a biphasic first-order kinetics with rate constants of 9.6 x 10(-4) and 2.5 x 10(-4) s-1, corresponding to diffusion of TEMPO-16 from the external monolayer of SPHS to the bulk water and flip-flop of TEMPO-16 from the internal to external monolayer of the vesicle, respectively. On the other hand, the reaction of TEMPO-16 with VC-16 was second-order and over three orders of magnitude faster than that with VC, presumably due to VC-16 induced fusion of the vesicle.
Liu
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National Laboratory of Applied Organic Chemistry, Lanzhou University, Gansu, China.
Guo
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Wu
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Liu
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YC
Liu
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ZL
D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000031:analogs & derivatives / Q000737:chemistry*; D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry; D008567:Membranes, Artificial; D012995:Solubility; D013113:Spin Labels
D000975:Antioxidants; D003497:Cyclic N-Oxides; D008051:Lipid Bilayers; D008567:Membranes, Artificial; D013113:Spin Labels; D001205:Ascorbic Acid; C031226:6-O-palmitoylascorbic acid; C003959:TEMPO