High-Resolution ¹H NMR Investigations of the Oxidative Consumption of Salivary Biomolecules by a Tooth-Whitening Formulation: Relevance to Safety Issues

A multicomponent evaluation of the oxidative consumption of salivary biomolecules by a hydrogen peroxide (H2O2)-containing tooth-whitening formulation has been performed using high-resolution proton (1H) nuclear magnetic resonance (NMR) spectroscopy. Unstimulated human saliva samples (n = 10) were treated with aliquots of supernatants derived from 1) the H2O2-containing whitening gel, 2) the corresponding tooth-whitening accelerant solution containing an amino-alcohol activator, and 3) a combination of these product agents pre-mixed in the recommended manner. 600 MHz 1H NMR spectra acquired on these samples demonstrated that H2O2 present in the whitening gel gave rise to the oxidative decarboxylation of salivary pyruvate (to acetate and CO2), the direct oxidation of trimethylamine and methionine (to trimethylamine-N-oxide and methionine sulphoxide respectively), and the indirect oxidative consumption of lactate and carbohydrates in general. Experiments conducted on a chemical model system confirmed the consumption of pyruvate by added H2O2, and also revealed that this method could be employed for determinations of the H2O2 content of tooth-whitening products. In conclusion, high-resolution 1H NMR analysis provides much valuable molecular information regarding the fate of tooth-whitening oxidants in human saliva, and also permits an assessment of the ability of endogenous antioxidants therein to protect against any soft tissue damage arising from the possible leakage of H2O2 from tooth-whitening application trays.

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

In view of its potent microbicidal actions, ozone (O3) 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 (1H) 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 O3 (4.48 mmol.) delivered by a therapeutic O3 generating device. Attack of O3 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 CO2 via an oxidative decarboxylation process (93% ± 4% yield). Reaction of O3 with α-D-glucose gave rise to formate as a major product (24% ± 2% yield). In conclusion, multicomponent 1H NMR analysis of appropriate chemical model systems provides valuable molecular information regarding the reactivity of O3 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 O3-scavenging biomolecules in oral fluid and/or soft tissue environments than that of O3 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).

Chronic non-communicable disease risks presented by lipid oxidation products in fried foods

Toxic lipid oxidation product (LOP) generation in culinary frying oils (CFOs) during high-temperature frying practices: passage into fried foodsLOPs detectable in fried foods are both cytotoxic and genotoxic, and currently a substantial proportion of the human population regularly consumes such toxins in Western diets.