Study On Preparation And Pharmacokinetic Of Baicalin-Polyvinylpyrrolidone Coprecipitate Capsule

Baicalin, a single active ingredient extracted from the dried roots ofScutellaria baicalensis of the Labiate family, is a flavonoid used to treatacute icteric, acute non-icteric and chronic hepatitis. Current studies haveshown that baicalin is able to inhibit multiple cancer cells from growing ormultiplying and protect the liver from drug-induced injuries. Poorsolubility of the currently marketed oral preparations including tablets andcapsules has resulted in poor dissolution and bioavailability. The absolutebioavailability of baicalin has been found to be only2.2±0.2%in rats afteroral administration.Solid dispersion technology is a new technology used to improvedissolution rates of insoluble drugs within solid dispersions into carriers inmicrocrystallite, amorphous and molecular phases that are called simpleeutectic mixtures, coprecipitates (also called vitreous state solid solutions)and solid solutions, respectively. Drug dispersity in a given carrier directlyaffects its dissolution rate and places molecular, amorphous and microcrystalline phases in a descending order of sequence in terms ofdissolution rate. In addition, different carriers also have a direct impact ondrug dispersion morphology.In this study, baicalin-PVP coprecipitate were prepared using solventmethod of solid dispersion technology to increase the dissolution rate andstability of baicalin in its carrier, and its preparation process, dissolution,prescription process, stability and pharmacokinetics were studied. The aimof this study was solving the shortcomings of baicalin, improvig the plasmaconcentration of baicalin after oral administration, and expanding itsapplication of anticancer action in clinical practice.The whole work of this paper have been completed, therefore, we candraw the conclusions as follows:1. The UV method was established to determine of content ofBaicalin-Polyvinylpyrrolidone (PVP)coprecipitate capsule and itsdissolution rate in four different solutions, to provide the basis forscreening prescription and quality control. In278nm wavelength, thecontent of Baicalin-PVP coprecipitate capsule and its dissolution rate in0.1mol·L^-1HCl solution, distilled water, pH4.5solution and pH6.8solution were determinated by SHIMADZU UV-3150. During thedetermination of the content, the calibration curves was linear in theconcentration range of3.473～9.261μg·m L^-1, r=0.9998(n=6), therecovery rate was99.06%～99.48%, RSD＜1%(n=3). During determining the dissolution rate in0.1mol·L^-1HCl solution, linearity wasgood within the concentration range of1.158～15.049μg·m L^-1, r=0.9998(n=7), the recovery rate was99.15%～99.58%, RSD≤0.70%(n＝3); in distilled water, linearity was good within the concentration rangeof1.158～12.734μg·m L^-1, r=0.9999(n=6), the recovery rate was98.25%～101.56%, RSD≤0.71%(n＝3); in pH4.5solution, linearity wasgood within the concentration range of1.158～12.734μg·m L^-1, r=0.9999(n=6), the recovery rate was98.25%～101.56%, RSD≤0.61%(n＝3); in pH6.8solution, linearity was good within the concentration rangeof1.158～12.734μg·m L^-1, r=0.9999(n=6), the recovery rate was98.37%～99.14%, RSD≤0.58%(n＝3). The method is simple and rapid,and the results is accurate, reliable, and reproducible. It can be used tocontrol the quality of Baicalin-PVP coprecipitate capsule with satisfactoryresults.2.The preparation technology of baicalin-PVP coprecipitate wasimproved, the production costs were reducd and the dissolution andproportion of drug and accessories of high-insoluble drug baicalin werefurther improved. The baicalin-PVP coprecipitate with drug and accessoriesproportion of1:2,1:3,1:4were prepared respectively by improvedtechnology of coprecipitation method and made stomach capsule. UVspectroscopy was used to determine its drug content and dissolution in0.1mol·L^-1HCl solution, distilled water, pH4.5solutions, pH6.8solution and compared with the bulk drug capsules. The characterization ofbaicalin-PVP coprecipitate was determined by X-ray powder diffraction.RESULTS The dissolution of baicalin-PVP coprecipitate capsules withdrug and accessories proportion of1:2,1:3,1:4was4.8times,21.5times,30.4times of bulk drug capsules respectively in0.1mol·L^-1HClsolution;was1.7times,3.3times,3.4times respectively in distilled water;was2.06times,2.02times and2.09times respectively in pH4.5solution;was similar with bulk drug capsules in pH6.8solution. X-ray powderdiffraction indicated that baicalin crystal peak disappeared in baicalin-PVPcoprecipitate with drug and accessories proportion of1:2,1:3,1:4.therefore, the improved preparation technology of baicalin-PVPcoprecipitate can effectively reduce the production cost; can significantlyimprove the dissolution and proportion of drug and accessories. Theincreased times are much higher than that reported in literature.3.Baicalin-polyvinylpyrrolidone (PVP) coprecipitate with drug andaccessories proportion of1:3was prepared by the improved solvent methodof solid dispersion technology and attempt to prepare more each time. Now28.00g baicalin-PVP coprecipitate could be prepared each time through theappropriate adjustments of preparation conditions. dissolution tests showedthat the dissolution of baicalin-PVP precipitate capsule could be matchedthe capsule dissolution requirements of Chinese Pharmacopoeia2010, hedissolution up to70percent in45min.The coprecipitate was characterized using X-ray powder diffraction (XRD), differential scanning calorimetry(DSC), infrared spectrometry (IR) and dissolution testing. Furthermore,AFM·IPC-208B high-resolution atomic force microscopy (AFM) wasutilized to characterize the molecular morphology of baicalin within itscarrier and the interaction between baicalin and its carrier. The results ofXRD and DSC indicated that baicalin resided in PVP polymers in anamorphous or molecular phase, dissolution test results demonstrated thatthe dissolution rate of the coprecipitate was3.6times that of the activepharmaceutical ingredient (API). The results of IR indicated the possibilityof the formation of intermolecular hydrogen bonds. The AFM·IPC-208Bfindings revealed that baicalin was dispersed in PVP polymers with amolecular size of2nm and either wrapped or surrounded by approximately0.4nm of a five-membered ring of PVP arranged along the carbon chainsequentially. An intermolecular hydrogen bond was formed between the4-OH of the glucuronide of baicalin and the O of the carbonyl group fromPVP in addition to the formation of intramolecular hydrogen bonds withinbaicalin. The AFM·IPC-208B technique was able to characterize the spatialconformation and interaction between the drug and carrier intuitively at themolecular level and confirmed the possible formation of hydrogen bondsbetween the drug and carrier speculated by IR; it can even distinguish thebinding-OH of the interaction, overcoming many of the disadvantages oftraditional methods. Therefore, AFM·IPC-208B can be used as a new characterization technique for coprecipitates in the future.4. The stability of baicalin-PVP precipitate was investigated. Theresults of influencing factor showed that high temperature (60°C or40°C), high humidity (25°C, RH90%±5%, or25°C, the R H75%±5%),strong light significantly influence the content, dissolution, traits andweight of baicalin-PVP precipitation capsule, and high humidity is thegreatest influencing factor. Long-term tests shows that, baicalin-PVPprecipitate capsule was stability in condition of25℃±2℃, R H60%±5%with commercial packaging (a pairs of aluminum foil sealed package)one year. The content, dissolution, traits and weight of baicalin-PVPprecipitate capsule did not change, which suggest that the validity of theproduct be tempertarily scheduled as1year.5. A high performance liquid chromatography method wasestablished to determine the content of baicalin in beagle dog plasma.Chromatographic conditions were, column: A Hypersil ODS250mm x4.6mm5μm guard column: Hypersil ODS4.0mm x3.0mm5μm, mobilephase: methanol:0.1%H3PO4,45:55(v/v) internal standard: daidzein,flow rate:0.8mL/min, UV detection wavelength:278nm, injectionvolume:50μL, column temperature:30℃. Liquid-liquid extraction,solidphase extraction and concentration were used to extract and separate thebaicalin from plasma samples in very low level. The results showed thatthe impurities in the plasma did not interfere with the determination of main drug and internal standard, a good linear relationship was obtained inrange of3.648-364.8ng/mL, R=0.998(n=6). The extraction recoverieswere80%-90%, and RSD were less than10%. The stability of baicalin inplasma samples at room temperature, freeze-thaw conditions andlong-term conditions were good. It shows that the method is accurate,reliable, and can be used for the quantitative detection of baicalin in theplasma of beagle dogs.6The pharmacokinetics of baicalin-PVP coprecipitate capsules inbeagle dogs were investigated. Self-control cross-administration was usedto do pharmacokinetic experiment in six beagle dogs. As compared withbaicalin bulk drugs capsules, the results of concentration--time curve andpharmacokinetic parameters showed that baicalin-PVP precipitatecapsules could improve drug absorption in stomach and colon significantly,and relative bioavailability was338.2%±93.2%. The results confirmedthe assumption that the more particle size of baicalin in the carrier wasreduced, the more dissolution rate and bioavailability would be increased.