# A Radish Root Ferment Filtrate for Cosmetic Preservation: A Study of Efficacy of Kopraphinol
## 1 Introduction  
According to EU Regulation 1223/2009, which establishes rules to be complied with by any cosmetic circulating on European territory, \"a cosmetic product made available on the market shall be safe for human health when used under normal or reasonably foreseeable conditions of use\" [1]. With regard to safety, the microbial contamination of cosmetics is of special concern for industry because microbial contaminants can not only alter products, making them useless, but also pose a potential risk to the health of consumers [2]. Considering the conditions of use and the sites where they are applied, cosmetics are not expected to be sterile, but they are required to exhibit a controlled microbial content; however, they can undergo microbial contamination both in the various phases of industrial production and during the use by the consumer, from their opening until they are discarded. The Scientific Committee on Consumer Safety [3] provides guidelines on the microbiological quality of the finished cosmetic products and defines two separate categories of cosmetic products on the basis of their use and of their non-pathogenic microbial load:  
Category 1: Products specifically intended for children under 3 years, to be used in the eye area and on mucous membranes (microbial limits \(1\times 10^{2}\) cfu per g or mL). Category 2: Other products (microbial limits \(1\times 10^{3}\) cfu per g or mL). To ensure that cosmetics and personal care products, especially those with a high content of water, are microbiologically safe and stable, microbial contamination must beprevented by combining different strategies; they include the application of good manufacturing practices (GMPs), the use of suitable primary packaging, and, most importantly, the introduction into the formulation of an appropriate antimicrobial preservative system, one of the critical components in cosmetic formulations [4]. Antimicrobial preservatives have a double function: (i) to prevent the proliferation of microorganisms leading to deterioration of the product, and (ii) to prevent the growth of pathogenic microorganisms that may pose a potential health risk to the user during their repeated use, often by multiple persons, over extended periods of time; meeting these two requirements ensures that cosmetics are safe to use, stable, and effective during shelf-life. The availability of a wide and safe range of preservatives is one of the key challenges of the cosmetic industry. At present, Regulation 1223/2009 regulates the use of preservatives in cosmetic products marketed in the European Union, ruling that the only substances allowed as preservatives in cosmetics are those listed in Annex V of the Regulation. Preservatives allowed by the Regulation include different types of chemicals, such as parabens, alcohols, acids, quaternary ammonium compounds, and isothiazolnones. Parabens have been the most popular preservatives for quite a long time because they are effective and cheap, but European regulators put restrictions on them due to their endocrine-disrupting potential, and their safety status remains controversial [5]; on the other hand, isothiazolnones, which in recent times have largely replaced parabens due to their broad spectrum and high efficacy, present a high risk of sensitization and have been recently banned in leave-on cosmetics [6]. Due to evidence or suspicion of adverse effects of synthetic preservatives, consumer demand for natural ingredients in cosmetics and personal care products is constantly growing. Consequently, cosmetic manufacturers are increasingly oriented to replace conventional synthetic preservatives with suitable alternatives. The replacement of conventional preservatives is very demanding, and current strategies include the use of nature identical synthetic preservatives (e.g., benzoic acid, sorbic acid, benzyl alcohol); the use of natural plant-based preservatives (plant extracts, essential oils); the use of auto-preservation techniques; and the use of multifunctional ingredients [7].