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. 2022 Mar 13;23(6):3105.
doi: 10.3390/ijms23063105.

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

Gloria Nicastro  1 , Louise Mary Black  2 , Paolo Ravarino  1 , Simone d'Agostino  1 , Davide Faccio  1 , Claudia Tomasini  1 , Demetra Giuri  1
Affiliations

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

Gloria Nicastro et al. Int J Mol Sci. .

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.

Keywords: Schiff base; fragrance; gel; hydrolysis; perfumery; self-assembly.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Structure of the four Schiff bases SB1–SB4 discussed in this work.
Figure 2
Figure 2
Structural features of crystalline SB2: (a) the asymmetric unit, showing the intramolecular S11(6) hydrogen bonding interaction between the iminic nitrogen and carbonyl group, (b) crystal packing viewed down the a-axis, and (c) detail of the columnar stacking extending along the [100] crystallographic direction; (d) optical microscope image (polarized light) of the crystals of SB2. Scalebar is 100 μm.
Figure 3
Figure 3
(left) Microscope image in epifluorescence mode of a piece of gel A containing SB2P; (right) microscope image in epifluorescence mode of a piece of gel B made with SB2P. Scalebar is 100 µm.
Figure 4
Figure 4
Hydrolysis results for the SB under neutral conditions. The data are reported as mean value and standard deviation.
Figure 5
Figure 5
Hydrolysis results for the SB under acidic conditions. The data are reported as mean value and standard deviation.
See this image and copyright information in PMC

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