Oxidation of Biomolecules by Ozone

Objectives: The powerful microbiocidal activity of ozone (O3) is well known and previous investigations have demonstrated its potential application as a therapeutic agent in the treatment of dental caries. O3 is very highly reactive towards selected carious dentine biomolecules, and such reactions are likely to be of relevance to its microbiocidal activity. Hence, in this investigation we have utilised high resolution proton (1H) nuclear magnetic resonance (NMR) spectroscopy to determine the nature and extent of the oxidation of biomolecules present in carious dentine, plaque and saliva. Methods: Aqueous solutions containing sodium pyruvate, alpha-D-glucose, L-cysteine and L-methionine (5.00 mM) were prepared in 40.0 mM phosphate buffer (pH 7.00) which was previously deoxygenated with argon gas prior to use. 5.00 ml aliquots of these solutions were treated with 5.00 ml of ozonated (5 ppm) water for a period of 5 min. [1]. These experiments were conducted in triplicate. Matching de-oxygenated solutions of these biomolecules untreated with O3 served as controls. Results: O3 treatment oxidised a-D-glucose, generating formate as a product via a fragmentation process, and treatment of pyruvate with this oxidant produced acetate and CO2 via an oxidative decarboxylation process. Furthermore, the volatile sulphur compound (VSC) precursors cysteine and methionine were oxidatively converted to their corresponding primary oxidation products cystine and methionine sulphoxide respectively. Conclusions: Multicomponent analysis of appropriate chemical model systems provides useful molecular information regarding the reactivity of ozone towards oral environment biomolecules. For example, oxidation of cysteine and methionine provides evidence for the capacity of this oxidant to combat oral malodour since these agents are precursors to VSCs. [1] TherOzone Unit model 2007, U.S.A.