Preparation And Characterization Of Rhoifolin And Its Complexes With Cyclodextrins

In recent years,natural flavonoids,due to their good biological activity and medicinal value,have attracted the attention of many researchers and have been widely used in the fields of medicine and food.Although flavonoids are widely found in the mosaics of plants,their content in plants and the bioavailability is very low.And flavonoids of different structures have different biological activity.Therefore,the development of novel flavonoids with higher biological activity are currently the main focus of research.It is an efficient and feasible method to synthesize a novel active flavonoid by using chemical semi synthesis to realize the transformation between the structure of flavonoids.Meanwhile,the poor water-solubility and thermal stability of the flavonoids greatly limit their application range.How to improve the water solubility and thermal stability of flavonoids is important for improving the bioavailability of flavonoids.In this thesis,we use naringin as raw material to synthesize rhoifolin by chemical semi synthesis method.The chemical structure was identified by means of ultraviolet,infrared,nuclear magnetic resonance,mass spectrometry.The antioxidant capacity was evaluated by in vitro antioxidant model?DPPH radical scavenging,ABTS radical scavenging,oxygen free radical absorptive capacity ORAC and peroxisome scavenging capacity PSC?.Then the preparation process conditions are optimized by the response surface method and the orthogonal test.Finally the rhoifolin/HP-?-CD complex was prepared by cyclodextrin complex method.The physical and chemical propitraerties of the compound was analyzed by ultraviolet-visible spectrometry?UV?,infrared spectrometry?IR?,scanning electron microscopy?SEM?,X-ray diffractometry?XRD?,thermogravimetry?TG?and differential scanning calorimetry?DSC?.Finally,the three-dimensional structure-activity relationship of the complex was studied by molecular docking.The main contents and results are as follows:?1?A naringin derivative,spectroscopic analysis indicated that the compound is rhophyllin,was prepared by semi-synthetic one-step synthesis of iodine and pyridine.The results of spectral analysis showed that the compound was rhoifolin.Antioxidant test results showed that compared with Trolox standard curve,the IC₅₀ value for DPPH radical scavenging capacity of was 100.35±7.25?mol TE/g DW,the IC₅₀ value for ABTS radical scavenging capacity was 187.26±6.14?mol TE/g DW,and the ORAC value was 3642.92±150.64?mol TE/g DW;compared with the standard curve of vitamin C,The PSC value of the rhoifolin was determined to be 7.73±0.51?mol vit C equiv./g DW.?2?The most suitable process conditions for the determination of rhoifolin by single factor and response surface methodology are:The molar ratio of naringin to iodine 1:1.1,reaction time 6.02 h,reaction temperature 87.65°C,pH value 3.50.Under these conditions,the average conversion rate of naringin is 76.57%,which is close to the theoretical design value of the response surface model of 77.26%.The optimum process conditions for the recrystallization purification step are determined by orthogonal experimental design.The ethanol concentration was 40%,the crystallization time was 6h,and the crystallization temperature was 10°C.The average crystallization rate of the rhodanin was 76.81%under the experimental conditions.?3?Phase-solubility experiments showed that the ability of HP-?-CD to contain rhoxin was stronger than?-CD,and the binding was carried out in a 1:1 ratio.Preparation of rhoifolin/HP-?-CD complex by aqueous-lyophilization.The X-ray diffraction and spectral analysis showed that the phase state of rhoifolin has changed,and did not disperse in the complex as an independent crystalline state.In the compounding process,no breakage and generation of covalent bonds occurredn the middle.Water solubility and DSC analysis showed that the water-solubility and thermal stability of the complexes were improved;Water solubility increased from less than40?g/mL to 240.42?g/mL at 25?.The results of molecular simulation docking showed the rhoifolin enters its internal hydrophobic cavity along the big mouth of HP-?-CD,while it's A-ring and glucosyl group are located at the big-end,and the supramolecular structure is mainly maintained by hydrogen bonds.The above results indicate that rhoifolin can be successfully prepared by using iodide/pyridine method from a wide range of sources of naringin.Preparation of rhoifolin/HP-?-CD complex has significantly improved its water solubility and thermal stability.It provides a reference for the deep utilization and research of naringin and rhoifolin,and expands the application scope of rhoifolin in medicine and health food.