Methyl salicylate (MS), the major flavor component in Wintergreen oil, has been extensively used in many consumer products, such as toothpaste, mouth rinse, and lotions. The stability of MS however, presents a challenge in particularly, at high pH environment where it is known to undergo a hydrolysis to salicylic acid. Addition of amino acids to MS solution results in an increased rate of MS hydrolysis and the mechanism of this reaction remains unknown. In this work UV-VIS, <sup>1</sup>H NMR and GC-MS were used as a comprehensive set of tools to monitor the hydrolysis of MS and analyze the end products in the presence of amino acids. Strong UV-VIS absorption of MS allows studying the reaction at the concentrations as low as 0.0025 wt%. Peak position near 303 nm can be successfully used to quantify MS relative concentration with time and at different pH conditions. All amino acids studied herein, including glycine, lysine and arginine, accelerate the hydrolysis reaction of MS in a very similar fashion. By selectively protecting either the amine and/or carboxyl groups of amino acids, the hydrolysis rate of MS can be effectively reduced. The data suggest that both amine and carboxyl groups of amino acid are crucial to MS hydrolysis, likely forming an intermediate complex with MS while hydroxyl ion acts as a nucleophile to attack the carboxyl group of MS. The computational work based on density functional theory is in progress to provide insight into the molecular mechanism of this reaction. These findings will be helpful in understanding flavor stability and ways to improve it in the consumer products containing amino acids.<br/>

Spectroscopic study of methyl salicylate hydrolysis in the presence of amino acids

2019 Spring National Meeting

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