| Polydatin is a main effective component in Polygonum cuspidatum, and its functions contain restraining cardiac muscle cell, moderating platelet aggregation, diminishing blood fat, resisting lipid oxidation and preventing shock. Thus, polydatin, with high development potential, is widely applied in clinical, medical and healthy areas, as well as fortified in food additives and cosmetics. However, due to its low solubility in water and isomerization tendency under ultraviolet radiation, polydatin is comparatively unstable, which declines its bioavailability and restricts its utilization. As a consequence, exploring polydatin and its products-enhancing its solubility and stability is very beneficial for its application and marketing, and also shows great significance for improving exploitation of Chinese herbal resources, increasing their added value and modernizing Chinese herbal medicine industry.The present study remarkably raised water-solubility of polydatin by manufacturing its cyclodextrin (β-CD and HP-β-CD) inclusion complexes, and advanced its stability to some extent.(1) The polydatin cyclodextrin (β-CD and HP-β-CD) inclusion complexes were prepared by freeze-drying method. Meanwhile, the inclusion complexes were identified by UV-visible spectra (UV-vis), infrared spectrometry (IR), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR), respectively. It was identified that the polydatin cyclodextrin (β-CD and HP-β-CD) inclusion complexes were formed.(2) The intermolecular reaction between the host and the guest agents, soluble effects of cyclodextrins (β-CD and HP-β-CD) on polydatin in aqueous solution and changes of thermodynamic parameters in the complexation were determined by phase solubility method. The results indicated: the significant reactions between the host and the guest molecules in aqueous solution were confirmed, and polydatin could form inclusion compounds (1:1) with the two cyclodextrins derivates (β-CD and HP-β-CD). The solubility of polydatin in aqueous solution was linearly escalated with the increased concentration ofβ-CD and HP-β-CD, showing a plot of the typical AL type phase solubility. All three thermodynamic parametersΔG,ΔH andΔS in the complexation gave negative values.(3) Inclusion ratios of polydatin cyclodextrin inclusion complexes were analyzed by equimolar series method. The results revealed that polydatin included by both of the two cyclodextrins (β-CD and HP-β-CD) at the ratio of 1:1(molar/molar), which was in consistent with the results of phase solubility method tests.(4) DPPH and FRAP were employed to evaluate the antioxidant activities of polydatin and its inclusion complexes. Through the data, we discovered that polydatin-β-cyclodextrin, polydatin-hydroxypropyl-β-cyclodextrin and polydatin all showed some ability of eliminating DPPH·free radical and reducing TPTZ. Observed by DPPH, the above 3 compounds did not display much difference in antioxidation capability, as their IC50 were 346.09mg/L, 337.40mg/L and 363.46mg/L, separately. And FRAP determined EC1 values of polydatin-β-cyclodextrin, polydatin-hydroxypropyl-β-cyclodextrin and polydatin as 431.15 mg/L, 405.07 mg/L and 463.88 mg/L; hence, reducing capacity of the 3 compounds did not present much distinction either, which accorded with results from DPPH method.(5) Stability of polydatin in inclusion complexes under ultraviolet radiation was investigated. Among the results, polydatin-β-cyclodextrin and polydatin-hydroxypropyl-β-cyclodextrin altered similarly, which indicated the 2 compounds had similar stability under UV condition; however, polydatin which had not been included by cyclodextrin was unsteady, the loss ratio was 20% higher under ultraviolet radiation, illustrating stability of polydatin was elevated in cyclodextrin inclusion complexes. |
