Controlled Hydrolysis of Odorants Schiff Bases in Low-Molecular-Weight Gels.

Gloria Nicastro,Davide Faccio,Simone D’Agostino,Demetra Giuri,Louise Mary Black,Paolo Ravarino,Claudia Tomasini

doi:10.3390/ijms23063105

Gloria Nicastro, Davide Faccio + Show 5 more

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https://doi.org/10.3390/ijms23063105

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Abstract

Imines or Schiff bases (SB) are formed by the condensation of an aldehyde or a ketone with a primary amine, with the removal of a water molecule. Schiff bases are central molecules in several biological processes for their ability to form and cleave by small variation of the medium. We report here the controlled hydrolysis of four SBs that may be applied in the fragrance industry, as they are profragrances all containing odorant molecules: methyl anthranilate as primary amine, and four aldehydes (cyclamal, helional, hydroxycitronellal and triplal) that are very volatile odorants. The SB stability was assessed over time by HPLC-MS in neutral or acidic conditions, both in solution and when trapped in low molecular weight gels. Our results demonstrate that it is possible to control the hydrolysis of the Schiff bases in the gel environment, thus tuning the quantity of aldehyde released and the persistency of the fragrance.

Highlights

Hydrolysis of Odorants Schiff BasesFragrances are low molecular weight molecules with a characteristic odor [1–3]
We report the controlled hydrolysis of four Schiff bases (SB) that can be used as profragrances in perfumery applications
With the aim of preparing materials able to release odorant molecules over several days, we studied the hydrolysis of four SB profragrances in different media to tune their hydrolysis time as a function of the medium acidity and the consequent release of odorant aldheydes and methyl anthranilate

Summary

Introduction

Hydrolysis of Odorants Schiff BasesFragrances are low molecular weight molecules with a characteristic odor [1–3]. A possible strategy is to entrap the odorant molecules in micelles, capsules or particles [4–7] that often have to face problems like low encapsulation load or poor material stability. Another strategy, adopted by nature for the storage of volatile species, is to create precursors with reduced volatility. This can be obtained by covalently binding the fragrance to another substrate, creating profragrances or properfumes. The covalent bond should be selectively cleaved by a specific stimulus, such as oxidation, light, enzymes, pH change, heat or hydrolysis, releasing the perfumed molecule [8–13]

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