Oxidative Consumption of Oral Biomolecules by Therapeutically-Relevant Doses of Ozone

Abstract

In view of its potent microbicidal actions, ozone (O 3 ) offers much potential for application as a therapeutic agent in oral health, e.g. in the treatment of dental caries. This oxidant is extremely reactive towards biomolecules present in the oral environment, and in this study we have employed high-resolution proton ( 1 H) nuclear magnetic resonance (NMR) spectroscopy to determine the nature and extent of the oxidation of biomolecules known to be present in carious dentin, plaque and saliva. Phosphate-buffered (pH 7.00) aqueous solutions containing sodium pyruvate, α -D-glucose, L-cys teine and L-methionine (5.00 mM) were treated with gaseous O 3 (4.48 mmol.) delivered by a therapeutic O 3 generating device. Attack of O 3 on methionine and cysteine generated the corresponding primary oxidation products of these substrates, specifically methionine sulphoxide [98% ± 4% (mean ± SEM) yield] and cystine (95% ± 6% yield) respectively, and treatment of pyruvate with this oxidant produced acetate and CO 2 via an oxidative decarboxylation process (93% ± 4% yield). Reaction of O 3 with α -D-glucose gave rise to formate as a major product (24% ± 2% yield). In conclusion, multicomponent 1 H NMR analysis of appropriate chemical model systems provides valuable molecular information regarding the reactivity of O 3 towards biomolecules present in the oral environment, information which is of much relevance to its therapeutic mechanisms of action. Moreover, in view of the much higher concentrations of these O 3 -scavenging biomolecules in oral fluid and/or soft tissue environments than that of O 3 applied, they may also serve to offer protection against putative adverse effects inducible by any of this oxidant which escapes from its site of therapeutic application (e.g., at primary root carious lesions).