Antioxidant and pro-oxidant activity of Vitamin C in oral environment.

Context: Antioxidant properties and Vitamin C. Background: Vitamin C is a naturally occurring organic compound and a potent antioxidant preventing oxidative damage to lipids and other macromolecules. It can also exhibit bimodal activity as a pro‑oxidant at a higher concentration. Vitamin C has a switch over role from being an antioxidant in physiologic conditions to a pro‑oxidant under pathologic conditions. A systematic review of this role would help to elucidate whether it is an antioxidant or a pro‑oxidant in the oral environment. Objective: To review studies reported in the literature elucidating the activity of Vitamin C and determine whether it is an antioxidant or a pro‑oxidant. Materials and Methods: Articles were searched in PubMed, MEDLINE using appropriate key words like “Vitamin C,” “antioxidant activity,” “pro‑oxidant activity,” “oral health” “oral disease.” Hand search of journals was also performed. Articles were reviewed and analyzed. Results: Search strategy reviewed 10 relevant articles which studied the dual role of Vitamin C. 65% of authors analyzed antioxidant action of ascorbic acid compared to 35% of the pro‑oxidant potential. Vitamin C acts as an antioxidant and a pro‑oxidant by a plethora of mechanisms. Factors determining its bimodal activity were studied, and the frequencies of their occurrence in the literature were depicted in percentage. Conclusion: The data validates the role of Vitamin C as an antioxidant under physiologic conditions exhibiting a cross over role as a pro‑oxidant in pathological conditions. Further studies are required to substantiate its pro‑oxidant activity to draw concrete conclusions.