Empirical Analysis Revealing Privileged Chemical Space of Cosmetic Preservatives

Michael P Storz,Lea Holsten

doi:10.3390/cosmetics8030080

Abstract

Most cosmetic products require preservation to prevent microbial contamination and to ensure consumer safety. Due to regulatory restrictions and rejection by consumers, preservative options have become limited and the development of novel solutions is needed. This search can be guided by knowledge about favorable chemical space for cosmetic preservatives. Therefore, we used preservatives allowed in the EU as training set and calculated various molecular properties. Empirical analysis revealed two separated areas of privileged chemical space with the net charge as distinctive property. The first area comprises the group of neutral and anionic preservatives and is characterized by low molecular size as well as limited hydrogen-bonding capacity, polarity, and flexibility. The second area includes cationic preservatives, which are rather diffusely distributed regarding molecular weight and hydrogen-bonding, however, all members share high flexibility. Both groups significantly differ from antibiotics, reflecting the specific requirement of cosmetic preservation. The molecular properties defining the privileged chemical space are easy to calculate, and thus, can provide guidance for the development of novel preservatives.

Highlights

Microbial contamination of cosmetic products is limiting shelf life and can pose a significant health risk for consumers [1]
In the EU, Annex V of the Regulation (EC) No 1223/2009 on cosmetic products provides a list of substances, which can be added to cosmetic products with the intention to preserve the composition from microbial contamination [3]
Aldehydes and formaldehyde releaser, isothiazolinones, sulfur dioxide releasing sulfites, and substances based on heavy metals were excluded from analysis, since their mechanisms-of-action are irrelevant for future developments

Summary

Introduction

Microbial contamination of cosmetic products is limiting shelf life and can pose a significant health risk for consumers [1]. To prevent spoilage by contamination with microorganisms, preservatives are typically added to ensure that the cosmetic composition remains free of microbial contamination for an adequately long period. Thereby, antimicrobial activity should be effective over a broad-spectrum of microorganisms and should persist longer than expected shelf-life plus the usage time. Rapid Alert System (RAPEX) of the European Commission (EC), 61 cosmetic products were recalled during 2016 and 2020, as they present a serious risk due to microbiological contamination [2]. In the EU, Annex V of the Regulation (EC) No 1223/2009 on cosmetic products provides a list of substances, which can be added to cosmetic products with the intention to preserve the composition from microbial contamination [3]. Many ingredients negatively impact odor or color of the cosmetic formulation, and disturbance of the emulsifying system can lead to significant change of viscosity or even ‘breaking’

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