Oral care compositions and methods of use
A technology for oral care and compositions, applied in the field of preparation of these compositions, which can solve the problems of lack of MeSA, incomplete understanding, and reduced consumer acceptance
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Embodiment 1
[0160] Example 1 - NMR analysis of MeSA during hydrolysis
[0161] Direct detection and quantification of MeSA in aqueous solutions is challenging due to its low water solubility. Although 1 H NMR provides structural and quantitative information about specific substrates in aqueous mixtures, but the biggest limitation of NMR is its poor sensitivity. MeSA was present in the test solution at a concentration of 3.29 mM. Typically, NMR quantitative analysis requires high concentrations of substrate. However, quantification of substrate by NMR at concentrations at or below about 0.1 wt% in water is not possible without effective solvent inhibition. To overcome this obstacle, a composite π / 2 pulse was applied before the pre-saturation pulse to effectively suppress the water peak of the sample.
[0162] By applying complex pulses to pre-suppress the water peak of the sample, resonances corresponding to protons of MeSA, salicylic acid (SA), glycine (Gly) and methanol can be identi...
Embodiment 2
[0164] Example 2-The effect of pH on the hydrolysis of MeSA
[0165] Studies were conducted to test how pH affects MeSA hydrolysis. Hydrolysis of carboxylate esters is known to be strongly pH dependent, so to better understand how pH affects MeSA hydrolysis in the absence of amino acids, the kinetics of MeSA hydrolysis in water were investigated in the pH range of 8 to 11.5. image 3 The data shown in clearly show that the decrease in MeSA concentration becomes faster with time (ie, the rate constant for the hydrolysis of MeSA increases) as the solution becomes more basic. OH at pH 8, 9, 10 and 11.5 - The molar ratios between MeSA and MeSA were 0003, 0.003, 0.03 and 0.96, respectively. Since the MeSA concentrations in these four samples ( image 3 ) is constant, which means that MeSA hydrolysis is caused only by the concentration of hydroxide ions in solution. Indeed, this result is consistent with literature reports that the hydroxide ion acts as a nucleophile to attack t...
Embodiment 3
[0166] Example 3 - Determination of the role of phenolic hydroxyl groups in the hydrolysis of MeSA
[0167] Next, the phenolic hydroxyl group was examined to test whether it affects the hydrolysis of MeSA at alkaline pH. The hydrolysis of two analog compounds, methyl benzoate and methyl paraben, was studied as a comparator. These two compounds have similar structures to MeSA, but lack a phenolic hydroxyl group in the former case and have a phenolic hydroxyl group in the para position in the latter case. However, no ester hydrolysis was observed for either compound at pH 9.0 in the presence or absence of Gly within 48 hours of hydrolysis ( Figure 4 ). In contrast, MeSA exhibited significant hydrolysis over time in the presence and absence of Gly. It is believed that the phenolic hydroxyl group of MeSA must be in the ortho position in order to have intramolecular hydrogen bonds to aid in the cleavage of the ester group in alkaline solution during hydrolysis.
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Abstract
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