Design of Antibacterial and Sustainable Antioxidant Networks Based on Plant Phenolic Derivatives Used As Delivery System of Carvacrol or Tannic Acid

Biobased release networks embedding active phenolic moieties were prepared by photoinduced thiol-ene reaction. The originality of this work is to design UV-cured materials as the delivery system of two phenolic compounds i.e. carvacrol (presents in thyme essential oil) and tannic acid (plants extracted). The key point of this study is to elaborate the cross-linked network and, in the same step, trapping the active phenolic molecules thanks to a rapid photo induced process at room temperature, preserving active natural compounds. The photoactivated thiol-ene reaction was chosen to synthesize different eugenol-based networks since this process is nowadays mainly well-known as a fast and straightforward tool to prepare cross-linked materials by green chemistry. The mechanical and thermal properties of the networks were determined, and their antibacterial and antioxidant properties were investigated against two bacteria strains: Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The system based on 20 wt % of carvacrol worked as an effective diffusion controlled system since it allowed a complete inhibition of the bacteria growth and a reduction in bacterial adhesion of 100% and 98.4% for E. coli and S. aureus respectively. The introduction of 10 wt % of tannic acid in the eugenol-based network led to a reduction of 77.9% of the bacteria adhesion of the Gram-negative bacterium (E. coli), and there was no bacterium adhesion of Gram-positive bacteria (S. aureus). Moreover, these phenolic compounds provided a promising strong antioxidant activity as a radical scavenging activity of 88% and 92% for 20 wt % introducing of carvacrol and 10 wt % of tannic acid respectively were determined. Finally, these new active networks are particularly interesting since after 2 months, the antioxidant property of the carvacrol still remains equal at 68% and is fully preserved for the tannic acid thus, they could be used as sustained antibacterial and antioxidant phenolic delivery systems for packaging applications. The long time activity of the networks containing tannic acid is due to a physical entrapping induced by an oxidative coupling reaction between the molecules of tannic acid.