Dynamic Mixtures: Challenges and Opportunities for the Amplification and Sensing of Scents

Abstract

Nature generates compounds as complicated mixtures, but surprisingly little is known about the synergies or inhibitory effects of compound mixtures, which is likely to become an important research area in life sciences in the near future. Some recently developed concepts in dynamic combinatorial/covalent chemistry (DCC) have been applied to amplify (increase the intensity and long-lastingness of perception) and sense (selectively detect and discriminate) individual bioactive volatile molecules in compound mixtures. This Concept article focuses on the potential of DCC to impact and modulate the biological and chemical properties of mixtures of bioactive volatile compounds to gain a more fundamental understanding of the properties of compound mixtures in molecular recognition.

Slow release of fragrance aldehydes and ketones in functional perfumery from dynamic mixtures generated with N‐heteroarylmethyl‐substituted secondary diamines

“…On the other hand, the multitude of parameters to be considered and selectively controlled in these systems adds considerably to the already existing complexity of relatively simple fragrance mixtures, in which the physico‐chemical and perceptional properties are far from understood. The investigation of dynamic combinatorial/covalent chemistry might therefore be an important opportunity to further understand the behaviour of complex compound mixtures while allowing their selective modulation to ultimately achieve well‐defined specific interactions with different biological targets . The present work clearly demonstrates that it is not yet possible to fully understand or even predict the impact of the addition of a reversibly reacting substrate to a relatively simple mixture of volatile compounds and thus to influence their properties in a controlled way.…”

“…Furthermore, the stability of the formed reaction products and the composition of the equilibrium play an important role for the efficiency of the delivery system in practical applications. While imines are often too unstable and oximes are too stable, it seems that the kinetics for the reversible formation and hydrolysis of aminals are particularly suitable for applications in functional perfumery . On the other hand, the multitude of parameters to be considered and selectively controlled in these systems adds considerably to the already existing complexity of relatively simple fragrance mixtures, in which the physico‐chemical and perceptional properties are far from understood.…”

“…The position of this equilibrium can be modulated by varying the external environmental parameters. This concept has recently also successfully been applied to the sensing and amplification of fragrances, and a series of different reversible reactions have been investigated to slow down the evaporation of fragrances or fragrance mixtures from different surfaces …”

“…The generation of so‐called dynamic mixtures as fragrance delivery systems is based on the addition of a reversibly reacting substrate to a mixture of fragrances with suitable functional groups. This procedure results in the temporary formation of a mixture of non‐volatile profragrances in equilibrium with a certain amount of non‐reacted substrate and the respective free fragrances . If the external conditions remain unchanged, for example during storage of the perfumed consumer article in a closed bottle, the equilibrium is expected to be stable.…”

“…If the external conditions remain unchanged, for example during storage of the perfumed consumer article in a closed bottle, the equilibrium is expected to be stable. However, once exposed to a surface, the free volatile fragrance molecules start evaporating and thus continuously shift the equilibrium towards the slow degradation of the profragrances, forming additional amounts of free fragrances (Scheme ) …”