| Oxyresveratrol is a natural tyrosinase inhibitor,however,it is unstable in light and heat,especially in polar solvents.And it can be easily oxidized by prooxidant agents or transformed into a cis-structure with low biological activities.Coup led with its very low water solubility and bioavailability,the application of oxyresveratrol is greatly limited.In view of the above problems,this paper studied the solubilizing and stabilizing effects of cyclodextrin(CD)encapsulated oxyresveratrol and explored the encapsulation mechanism,properties of the inclusion complex and its anti-browning effect on apple slices for the purpose of providing a new way for the application of oxyresveratrol.The inclusion complexes of oxyresveratrol withβ-cyclodextrin(β-CD)and hydroxypropyl-β-cyclodextrin(HP-β-CD)were prepared and characterized by FT-IR,XRD,TG-DTG and SEM.Based on the optimal formulation,0.21 g and 0.20 g of oxyresveratrol was included in 1.00 g of the oxyresveratrol loadedβ-CD(oxyresveratrol-β-CD)and HP-β-CD(oxyresveratrol-HP-β-CD)dried powder with the water solubility up to 14.44mg/mL and 47.33 mg/mL,yielding about 30 and 100-fold increase in oxyresveratrol solubility,respectively.The dissolution rate study showed that oxyresveratrol-β-CD and oxyresveratrol-HP-β-CD inclusion complexes exhibited a significant higher dissolution rate and concentration of oxyresveratrol at each measurement point in 480 min than that for pure oxyresveratrol,which exhibited 100%and 94.8%dissolution respectively after 10 min of the dissolution process,demonstrating the improvement of dissolving capacity by forming inclusion complexes.The encapsulation mechanism of oxyresveratrol andβ-CD as well as HP-β-CD was studied.As results shown,oxyresveratro l and two CDs were able to form inclusion complexes in a 1:1 stoichiometry.However,the interaction with HP-β-CD was more efficient,showing up as higher encapsulation constant(K_F).The K_F values exhibited a strong dependence on temperature and pH,which decreased as them increased.From the thermodynamic parameters of the oxyresveratrol-β-CD and oxyresveratrol-HP-β-CD,it could be seen that the complexation process was spontaneous and exothermic,and the main driving forces between oxyresveratrol and CDs were hydrogen bonding as well as van der waals force.Besides,molecular docking combined with ~1H NMR were used to explain the most possible mode of combination between oxyresveratrol and CDs,and found that the oxyresveratrol molecule was not completely encapsulated in theβ-CD cavity,whereas it almost completely entered the cavity of HP-β-CD,the guest molecule was inclined in the cavity and was stabilized by three hydrogen bonds.The interaction among hydroxypropyl methylcellulose(HPMC),oxyresveratro l and CDs were investigated.It has been found that oxyresveratrol can form inclusion complexes withβ-CD and HP-β-CD in a ratio of 1:1 in the presence and absence of HPMC.And the addition of HPMC further improved the stability of the inclusion compound,showing as a higher K_F value.Moreover,it could interact with both oxyresveratrol and oxyresveratrol-CD,when they were dissolved in solution simultaneously,oxyresveratrol would enter the cavity of CD preferentially,while HPMC was wrapped on the outside of complex.Stability studies have shown the good light-thermal stability of CD inclusion complex powder,however,the CD inclusion compound only increased the thermal stability of about10%in the solution,and the stability was very poor under light,w here still existed intense isomerization.The addition of HPMC in solution showed good protective effect on oxidative degradation and isomerization of oxyresveratrol,and the stability of the three component complexes was best,which kept 75%retention rate at 50°C with light on after 30 days storage.The apple slices experiment also showed that the inclusion ofβ-CD and HP-β-CD did not affect the tyrosinase inhibition effect of oxyresveratrol,and the combination of oxyresveratrol with Vc and HPMC showed the best anti-browning effect on apple slices. |
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