EVALUATION OF BIOLOGICAL ACTIVITY OF ENZYMATICALLY SYNTHESIZED PHLORIDZIN OLIGOMERS

Abstract

Dihydrochalcones are a class of flavonoids found in apple trees (Malus sp) generally present in high levels in young leaves and immature fruits. Phloridzin is a member of the dihydrochalcones which possess good antioxidant activity, as well as a protective role against UV radiation, hence it is a constituent of various commercial cosmetic preparations. These natural low-molecular weight phenolic compounds with diverse physicochemical characteristics are substrates for laccases, copper-containing polyphenol oxidases whose activity can yield compounds that vary in structure and biological activities. The positive effect of laccase-catalyzed polymerization of flavonoids on the functionality of produced oligomers or polymers has been already shown on some flavonoids’ representatives. In this work, fungal laccase from Trametes versicolor was applied as a biocatalyst in the reaction of phloridzin oligomerization. Synthesized phloridzin oligomers were separated from the reaction mixture and lyophilized in order to test their antioxidant and antimicrobial activity. Different antioxidant assays, such as ABTS (2,2’-azino-bis(3- ethylbenzenothiazoline-6-sulfonic acid) diammonium salt) and DPPH (2,2-diphenyl-1- picrylhydrazyl) showed that in comparison with the monomer, synthesized oligomers had the weaker ability to scavenge the free ABTS•+ and DPPH• radicals, since for both assays, examined IC50 values of phloridzin oligomers (0.46 mg/ml and 1.52 mg/ml, respectively) was higher than the values for parent molecule (0.13 mg/ml and 1.07 mg/ml, respectively). This could be ascribed to the fact that some of the functional groups responsible for the antioxidant activity probably participate in the formation of linkage between phloridzin units in the structure of oligomers. On the other hand, synthesized phloridzin oligomers demonstrated a significantly higher antimicrobial effect on the Gram-positive bacteria Staphylococcus aureus compared to the parent molecule phloridzin. Moreover, the greater inhibition of bacterial growth was achieved by increasing the oligomers’ concentration. Given the obtained results, synthesized compounds show potential to be further examined as dermal prebiotics.