Laccase Catalyzed Oxidative Polymerization of Phloridzin: Polymer Characterization, Antioxidant Capacity and α-Glucosidase Inhibitory Activity

Abstract

Phloridzin is a naturally occurring dihydrochalcone with various therapeutic properties. However, its low aqueous solubility and poor enzyme inhibitory capacity have limited its application in functional foods and medicines. Inspections of the properties of natural polymeric flavonoids suggest that these limitations could be mitigated by the polymerization of phloridzin, although to date, no relevant studies have been conducted. Here, oxidative polymerization was used to prepare polymeric phloridzin using laccase as the catalyst, and its structure, antioxidant capacity and α-glucosidase inhibitory activity were characterized. The results showed that laccase catalyzed polymerization via oxidative generation of phenolic radicals in the B ring of phloridzin to achieve the polymerization. The 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging capacity of the polymer (IC50, 0.48 mg/mL) was inferior to that of phloridzin (IC50, 0.20 mg/mL), but the α-glucosidase inhibitory activity of the polymer (IC50, 0.12 mg/mL) was significantly higher than that of phloridzin (IC50, 0.21 mg/mL). These effects could be attributed to the reduction of available phenolic groups and binding of the polymer to the enzyme, respectively.