Enzymatic Modification And Bioactivity Of Phloridzin

Phloridzin is one of the by-products of apple processing.It was reported that phloridzin possessed the anti-hyperglycemia,antihypertensive,antioxidant,antibacterial,antitumor,antiosteoporosis and antiaging activities.But its poor solubility in water and lipid limited its application range.The traditional chemical modification method has the disadvantages such poor regioselectivity,toxic residue,raw material loss,low yield and pollution,etc..In view of the requirements of modern food industry,it is not suitable for the modification of Phloridzin.In this study,tyrosinase,Candida antarctica lipase B and laccase were applied to modify phloridzin.The corresponding enzymatic reaction processes were investigated.The chemical structures of the obtained phloridzin were clarified based on the spectral analysis.Their antioxidant,?-glucosidase inhibitory and antiproliferative activity against HepG2 cancer cells were measured.The obtained results were as following:Tyrosinase from mushroom could catalyze the oxidation of phloridzin to produce the yellow pigment.In the experimental range,the enzymatic reaction could reach the equilibrium at 12 h.With the increase of enzyme concentration,the conversion rate of phloridzin at 36 h could rise from 34.07%?enzyme concentration of 0.5?g/mL?to 100%?enzyme concentration of 4.0?g/mL?.The obtained yellow pigment was identified as POPj based on the analysis of UV,IR,MS and NMR.In the peroxyl radical scavenging assay,the PSC values of POPj and phloridzin were 467.53±11.04 and 38.57±3.71?mol Vit.C/g sample,respectively,which suggested that the peroxyl radical scavenging activity of POPj was superior to that of phloridzin.For the cellular antioxidant assay,the CAA values of POPj and phloridzin were 960.14±100.45and 209.5±12.24?mol quercetin/100g sample,respectively.The antioxidant of POPj was higher than that of phloridzin.With vinyl acetate as a solvent and an acyl donor,Candida antarctica lipase B could catalyze the acetylation of phloridzin.It was found that the effects of enzyme dosage and reaction on the conversion of phloridzin and composition of the product were significant.At the enzyme dosage of 300 mg and reaction time of 24 h,the final acetylated derivative of phloridzin could be obtained,which was identified as 4,3?,6?-3-O-acetyl-phloridzin by UV,IR,MS and NMR.The antiproliferative activity of the tri-acetylated phloridzin against HepG2 cancer cells was superior to that of phloridzin.The tri-acetylated phloridzin could retard cell growth,induce cell apoptosis,lower mitochondrial membrane potential and scavenge intracellular ROS.It could be concluded that the antiproliferative activity of tri-acetylated phloridzin attributes to its capacity inducing HepG2 apoptosis and dysfunction MMP.The polymerization of phloridzin could be catalyzed by laccase.According to the analysis of UV,IR and NMR,the phloridzin polymer could form by the condensation between the hydroxyl group and hydrogen of rings B of the adjacent molecules.The DPPH radical scavenging activity of the phloridzin polymer(IC₅₀,0.49 mg/mL)was higher than that of phloridzin?IC50,>0.7 mg/mL?.But its ABTS radical scavenging activity(IC₅₀,0.48 mg/mL)was inferior to that of phloridzin(IC₅₀,<0.2 mg/mL).The?-glucosidase inhibitory activity of the phloridzin polymer(IC₅₀,0.12 mg/mL)was significantly higher than that of phloridzin(IC₅₀,0.21 mg/mL).The fluorescence analysis suggested that the phloridzin polymer played the inhibitory activity by binding ?-glucosidase.