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Light-Induced Byproducts of Vitamin C in Multivitamin Solutions

¹ Research Centre and Pediatric Department, Sainte-Justine Hospital, University of Montreal, Montreal, Quebec, Canada.
² Department of Nutrition, University of Montreal, Montreal, Quebec, Canada.
³ Division of Neonatology, Children’s and Women’s Health Centre of British Columbia, Vancouver, British Columbia, Canada.

^aAddress correspondence to this author at: Research Centre, Hospital Ste-Justine, 3175 Chemin Côte Ste-Catherine, Montreal, Quebec, H3T 1C5 Canada. Fax 514-345-4801; e-mail jean-claude.lavoie{at}umontreal.ca.

Background: When solutions of multivitamin preparations (MVPs) are exposed to light, H₂O₂ as well as organic peroxides are generated and the concentration of vitamin C decreases. The aim of this study was to determine, using mass spectrometry, whether the generation of oxidative byproducts of vitamin C, such as dehydroascorbate (DHA) and 2,3-diketogulonic acid (DKG), accounted for the reported decrease in ascorbic acid in MVPs exposed to light.

Methods: Mass spectrometry was used to document the formation of byproducts of ascorbic acid in solutions containing a MVP, vitamin C + riboflavin, and vitamin C + H₂O₂ + Fe²⁺. The involvement of ascorbic acid and H₂O₂ in the formation of organic peroxides was tested by measuring peroxide concentrations in solutions containing H₂O₂ with or without ascorbic acid and with or without Fe²⁺ before and after addition of catalase.

Results: The loss of ascorbic acid in photo-exposed MVPs was associated with the concomitant generation of byproducts different from DHA and DKG. Among them, one mass fingerprint was particularly observed with solutions of vitamin C + riboflavin exposed to ambient light as well as with the solution of vitamin C + H₂O₂ + Fe²⁺, suggesting a Fenton-like reaction. This fingerprint was associated with the formation of catalase-resistant peroxides.

Conclusion: Exposure of MVPs to light leads to the rapid loss of ascorbic acid and generation of specific byproducts that differ from DHA and DKG. The conversion of vitamin C into byproducts could be of biological importance in accounting for the decrease in ascorbic acid concentrations and the generation of organic peroxides in light-exposed MVPs.

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