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

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.

Controlled Lactonization of o-Coumaric Esters Mediated by Supramolecular Gels

“…Their chemical structure is easily tuneable, they can respond to different stimuli (triggers) to form/disrupt the gel network, and they are often biocompatible and biodegradable [ 17 , 18 , 19 , 20 , 21 ]. The controlled release of fragrances from gel media has been reported by us [ 22 ] and other research groups [ 6 , 8 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ].…”

“…Specific reaction conditions, such as hydrolysis, temperature changes, as well as the action of light, oxygen, enzymes, or microorganisms, can be used to liberate the many different chemical functionalities. For example, Schiff bases have been studied because they have a low volatility and, at the same time, they can be hydrolyzed in an acidic environment [ 22 , 38 , 39 , 40 ]. The hydrolysis is a crucial step and by regulating it, it is possible to prolong or shorten the time in which the fragrance is perceived.…”

Delivery of Active Peptides by Self-Healing, Biocompatible and Supramolecular Hydrogels

“…The gelation propensity of gelator 1 was previously reported by our group under several conditions [ 21 , 26 , 27 ] that never allowed us to obtain a hydrogel at neutral pH, needed for biological applications. The dissolution of gelators bearing a free acidic moiety at the C -terminus in water can occur in the presence of NaOH or other bases, usually at a pH of about 10.…”

“…LMW gels can therefore be considered a valid alternative to polymers in many applications. In cosmetics, these compounds can be used for different purposes (rheological modifiers [ 18 ], skin care and topical therapies [ 19 , 20 ], perfume controlled releaser [ 21 ]), but have still received poor investigation.…”

Biomolecule-Based Biomaterials and Their Application in Drug Delivery Systems

“…In fact, they have been used for many years in traditional medicine and even in cosmetic and fragrance formulations with antioxidant, analgesic, relaxing, and other therapeutic abilities. In odorant formulations, supramolecular gels are a novelty to control the release of fragrances via peptide-based low-molecular-weight molecules that are completely biocompatible and able to self-assemble into long fibers [ 2 ]. They are gaining a greater presence and impact because of their ecological features, lower environment impact, renewable sources, and, most importantly, their inherent antimicrobial and therapeutic potential.…”