Laccase-mediated synthesis of phloridzin oligomers: An insight into the influence of reaction conditions and evaluation of oligomers’ biological activity

The effect of key experimental factors on phloridzin oligomerization catalyzed by Trametes versicolor laccase was investigated, and biological activity of synthesized oligomers was evaluated. Mass spectrometry analysis of the obtained reaction mixture showed the presence of oligomers with the degrees of polymerization two and three with dimer as the major product. The detected masses of the formed oligomers indicated the repetition of phloridzin units in their structure and the loss of two hydrogen atoms during the linkage formation, while NMR analysis of the major dimer confirmed the presence of two phloridzin molecules linked via a C5-C5 bond. The effect of temperature, substrate, and enzyme concentration on phloridzin conversion and products’ yield was examined, and for achieving the highest products yield (4.1 mg/ml), optimal factors were 40 °C temperature, 5 mg/ml phloridzin concentration and 0.5 mg/ml laccase concentration. Synthesized oligomers showed good antioxidant activity compared to phloridzin and very good potential to be used as skin prebiotics since they exhibited inhibitory effect on opportunistic pathogen Staphylococcus aureus and stimulating effect on commensal bacteria Staphylococcus epidermidis in a broad range of tested concentrations. The highest prebiotic capacity was demonstrated at a concentration of 0.0195 mg/ml in S. epidermidis and S. aureus co-culture.