| Icariin and Baohuoside I are the flavonoids in Epimedium.Both of them play an important role in anti osteoporosis,treatment of diseases of the cardiovascular system.However,their low solubility leads to low bioavailability,which limits the application in clinical.It is urgent to improve the solubility of Icariin and Baohuoside I and expand their clinical application.The current methods to solve the problem of poor solubility mainly include the preparation of solid dispersions,phospholipid complexes and cyclodextrin inclusion compounds,but each method has certain disadvantages.It is important to find a safer and more effective method.The polysaccharides from natural source not only have anti-tumor,anti-oxidation,and immunomodulatory effects,but also their role as a functional component to increase the solubility of insoluble components has gradually attracted attention.This discovery provides the possibility for further research and application of polysaccharides from traditional Chinese medicine.According to the component structure theory,the material basis of traditional Chinese medicine is an orderly whole,which is composed of functional components and effective components.And synergistic effects of the two parts can enhance the therapeutic action.As an important component of Epimedium,polysaccharides have unclear solubilization functions and mechanisms for Icariin and Baohuoside I.Therefore,this investigation takes Epimedium polysaccharide as a functional component to study the structural characteristics of Epimedium polysaccharide,analysis the effect of structure on its function,and discuss its mechanism of solubilization.It provides a reference basis for solving the problem of low bioavailability of insoluble compounds.The main research content and conclusions of this article are as follows:Firstly,the optimal extraction conditions were obtained by optimizing the best process parameters of the crude polysaccharide extract of Epimedium.The Epimedium neutral polysaccharide EPS-1-1 and acidic polysaccharide EPS-2-1 were finally obtained after protein removal,depigmentation,DEAE-52 cellulose column separation,and Sephadex G-100 purification.First,the Box-Benhnken central combination test and response surface analysis method were conducted to obtain the optimal extraction conditions for the crude Epimedium polysaccharide extract:extraction time 2.4 h,numbers 2 and ratio of solution and material 1:23.Three sets of experiments were carried out in parallel under this condition.The average yield of polysaccharides was 2.15%,and the theoretical prediction value of the yield of polysaccharides obtained by the regression equation was 2.18%,and the relative error between the two was 1.11%.It shows that the model optimized by the response surface method is reliable and the parameters are reasonable and credible.The crude polysaccharide extract was deproteinized by the papain method combined with the seveag reagent method,and the HP20 macroporous resin was selected to depigment to obtain the crude Epimedium polysaccharide.The crude polysaccharide was separated by DEAE-52 cellulose column to obtain EPS-1 and EPS-2,and both of them were further purified by Sephadex G-100 to obtain Epimedium neutral polysaccharides EPS-1-1 and acidic polysaccharide EPS-2-1.Secondly,the structures of the purified Epimedium polysaccharide EPS-1-1 and EPS-2-1 were characterized by chemical composition analysis,high-performance gel permeation chromatography(HPGPC),Fourier transform infrared spectrometry(FT-IR),PMP derivatization,scanning electron microscopy(SEM)and Congo red test.The results of high performance gel permeation chromatography show that both are single symmetrical peaks,indicating that they are homogeneous polysaccharides.According to the calculation of the standard curve,the molecular weight of EPS-1-1 is 9733 Da,and the molecular weight of EPS-2-1 is 204888 Da;The chemical composition analysis results show that the uronic acid content(41.67%)of EPS-2-1 is significantly higher than that of EPS-1-1,which is consistent with the characteristics of acidic polysaccharide.In addition,EPS-1-1 is composed of fructose,mannose,ribose,rhamnose,glucose,galactose,xylose,and arabinose in a molar ratio of 1.90:0.67:0.05:0.08:3.29:1.51:0.05:0.37.The monosaccharides contained in EPS-2-1 include fructose,mannose,rhamnose,glucuronic acid,galacturonic acid,glucose,galactose,xylose and arabinose in a molar ratio of 5.25:0.18:0.32:0.13:1.14:0.16:0.55:0.08:0.22.Infrared chromatogram results show that EPS-1-1 contains a characteristic absorption peak of 848 cm-1 with α-glycosidic bonds in addition to the characteristic absorption peak of polysaccharides;and the characteristic peak of EPS-2-1 at 917 cm-1 indicates that the β-glycosidic bond exists in EPS-2-1,and the characteristic absorption peak of-COOH can be found in EPS-2-1.The Congo Red experiment shows that EPS-1-1 and EPS-2-1 do not have a triple helix structure,but they exist in the form of random coils.Scanning electron microscopy images show that EPS-1-1 contains a spherical structure with sheet-like structures stacked around it,and both surfaces are distributed with large and dense honeycomb-like holes.EPS-2-1 is mainly in the form of flakes,with rough surface and depressions of different sizes.Finally,the solubilization function and possible mechanism of Epimedium polysaccharide were preliminary explored through evaluating the effect of Epimedium polysaccharide solution on the solubility of Icariin and Baohuoside I.The results showed that the solubilizing effect of Epimedium crude polysaccharide on Icariin and Baohuoside I was dose-dependent in the concentration range of 0-20 mg/mL.The solubilizing effect of crude Epimedium polysaccharide on Icariin and Baohuoside I increased with the increase of the concentration.The solubilization effect of EPS-2-1 on Icariin and Baohuoside I is stronger than EPS-1-1.It is speculated that the solubilization function of Epimedium polysaccharide may be related to its structure.It is inferred that the solubilization mechanism of Epimedium polysaccharides may be the interaction of polysaccharides with Icariin and Baohuoside I to form a new complex through differential scanning calorimetry,the determination of critical micelle concentration and the analysis of particle size and zeta potential.The new complex exists in the form of micelles,and the complex formed with EPS-2-1 is more stable.In this investigation,the structural characteristics of two homogenous Epimedium polysaccharides EPS-1-1 and EPS-2-1 were analyzed,and the solubilization of two polysaccharides with different structural characteristics on Icariin and Baohuoside I was compared.The possible mechanism was also explored.It not only provides the possibility to improve the poor solubility and low bioavailability of insoluble ingredients,but also further expands the application of polysaccharides in traditional Chinese medicine. |
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