# A Radish Root Ferment Filtrate for Cosmetic Preservation: A Study of Efficacy of Kopraphinol
## 4 Discussion  
Recent trends in cosmetic antimicrobial preservation include the use of compounds of natural origin (e.g., essential oils, herbal extracts, and ferment filtrates) and the use of multifunctional ingredients (substances that offer preservation alongside other benefits, such as anti-aging or moisturizing effects). Kopraphinol fits perfectly into these trends for a number of reasons. First of all, our in vitro experiments confirmed the good broad spectrum antimicrobial activity of Kopraphinol, with a stronger inhibitory effect against the _E. coli_ and _Candida_ strains; moreover, challenge tests, performed on an O/W emulsion deliberately contaminated with high microbial loads, demonstrated the good conservative properties of Kopraphinol, complying with the requirements of current legislation and comparable with the efficacy of methylparaben, and sometimes better. It is also relevant that Kopraphinol is a natural ingredient obtained through a fermentation process. Fermentation is a process currently used to produce a wide range of cosmetic ingredients, such as emollients, surfactants, humectants, thickeners, and, indeed, preservatives [17]. Bioferments are innovative cosmetic ingredients, whose advantages include better biocompatibility, bioavailability, sustainability, and an increased efficacy compared to conventional ingredients [18]. Different cosmetic ingredients obtained by the _Lactobacillus_ fermentation of different substrates are classified as multifunctional ingredients with moisturizing properties and a strong preservative efficacy due to bacteriocins and organic acids of bacterial origin [17]; Kopraphinol belongs to this category, and like all multifunctional ingredients, it would allow formulators to develop products that are less expensive, easier to manufacture, and better-performing [19]. Other arguments in favor of Kopraphinol are its ease of use and safety. As an aqueous liquid, Kopraphinol can be precisely dosed by volume, and due to itstemperature resistance, it can also be easily incorporated in hot aqueous formulations, in which it will be perfectly dispersed. However, an important limit to the use of Kopraphinol emerged during our investigation: the incompatibility of the preservative with polymeric emulsifiers (e.g., Sepigel(r)) and gels (e.g., Carbomer), which results in a drastic reduction in the viscosity of the formulations; therefore, any use of this preservative should be preceded by studies of physical compatibility. Regarding safety, the use of Kopraphinol does not seem to pose a significant problem. The Expert Panel for Cosmetic Ingredient Safety (CIR) [20] assessed the safety of seven radish root-derived ingredients, most of which are reported to function as hair- and skin-conditioning agents in cosmetic products. The Panel reviewed the available data and concluded that these ingredients are safe in cosmetics in the present practices of use and concentration described in that safety assessment when formulated to be non-sensitizing. However, as recently highlighted, the application of cosmetics on the skin can affect the resident microflora [21]; in this context, it should be verified that the antimicrobial activity of Kopraphinol does not constitute a problem for the skin microbiome, which could result from a lack of selectivity of the preservative. In conclusion, the good antimicrobial activity, the natural origin, and the easy handling, together with the safety of use, make Kopraphinol a promising and effective candidate for the antimicrobial preservation of cosmetics, capable of successfully complementing or even replacing conventional preservatives. Conceptualization, C.C.A.J. and G.A.M. ; investigation, C.C.A.J. and G.A.M. ; writing, C.C.A.J. All authors have read and agreed to the published version of the manuscript. This research was funded by FAR2020 Juliano (University of Sassari, Italy). Not applicable. The raw data supporting the conclusions of this article will be made available by the authors on reasonable request. The authors declare no conflicts of interest.