Anthocyanins as novel sustainable antimicrobial preservatives

Preservation is an important process that prevents products from undesirable change or decomposition by bacterial growth. As the currently available chemical preservatives are associated with severe health threats and negative environmental impact, they do not meet the ‘safe-by-design’ and ‘biodegradability’ criteria in the European Green Deal. To meet these European goals, it is important to make the preservative market more sustainable, for instance by the use of natural molecules. In this project, we focused on the extraction, fractionation and characterization of natural, plant-based preservatives. Preliminary studies of the Hanze University of Applied Science have demonstrated the antimicrobial efficacy of crude flower anthocyanin extracts against an array of microbial species. Therefore, these molecules have the potential to serve as novel, sustainable chemical plant-based preservatives.

In this project, we focused on the development of a strategy for fractionation and characterization of crude flower-anthocyanin extracts in individual molecules, followed by in vitro screening of the antimicrobial efficacy against different microbial model-organisms. This method was optimized using crude anthocyanin extracts from tulips, on lab-scale (microliter to milliliter-scale) and lab- to semi-pilot-scale (milliliter to centi-/deciliter scale). Additionally, we were able to synthesize pure cyanidin-3-rutinoside from rutinoside (quercetine-3-rutinoside) derived from buckwheat.

In-depth analysis of the antimicrobial efficacy against E. coli, S. aureus, and K. pneumoniae was performed using crude extracts and single molecules under different pH conditions. Crude extracts demonstrated potent growth inhibition, especially against S. aureus and K. pneumoniae. This inhibition was most pronounced under pH7.4, as compared to more acidic conditions. Several pure anthocyanin-molecules demonstrated antimicrobial activity, whereas others did not.

This is the first attempt that combines in-depth chemical characterization of individual anthocyanins in relation to their antimicrobial efficacy. Our approach is the first step towards the targeted development of anthocyanin molecules as novel, circular and biodegradable non-toxic plant-based preservatives.

Chemical preservation is an important process that prevents foods, personal care products, woods and household products, such as paints and coatings, from undesirable change or decomposition by microbial growth. To date, many different chemical preservatives are commercially available, but they are also associated with health threats and severe negative environmental impact. The demand for novel, safe, and green chemical preservatives is growing, and this process is further accelerated by the European Green Deal. It is expected that by the year of 2050 (or even as soon as 2035), all preservatives that do not meet the ‘safe-by-design’ and ‘biodegradability’ criteria are banned from production and use. To meet these European goals, there is a large need for the development of green, circular, and bio-degradable antimicrobial compounds that can serve as alternatives for the currently available biocidals/ preservatives.
Anthocyanins, derived from fruits and flowers, meet these sustainability goals. Furthermore, preliminary research at the Hanze University of Applied Science has confirmed the antimicrobial efficacy of rose and tulip anthocyanin extracts against an array of microbial species. Therefore, these molecules have the potential to serve as novel, sustainable chemical preservatives.
In the current project we develop a strategy consisting of fractionation and state-of-the-art characterization methods of individual anthocyanins and subsequent in vitro screening to identify anthocyanin-molecules with potent antimicrobial efficacy for application in paints, coatings and other products. To our knowledge this is the first attempt that combines in-depth chemical characterization of individual anthocyanins in relation to their antimicrobial efficacy. Once developed, this strategy will allow us to single out anthocyanin molecules with antimicrobial properties and give us insight in structure-activity relations of individual anthocyanins. Our approach is the first step towards the development of anthocyanin molecules as novel, circular and biodegradable non-toxic plant-based preservatives.