Intestinal Absorption Study Of Baicalein Based On Traditional Chinese Medicine Biopharmaceutics Classification System And PBPK Model

Objective:Biopharmaceutics classification system(BCS)and biopharmaceutics classification system of Chinese materia medica(CMMBCS)can both analyze the absorption properties of drugs by studies about BCS classification properties.BCS not only can indirectly reflect the physicochemical properties and in vivo absorption properties of drugs,but also can establish in vitro and in vivo association predictions,which can lay a foundation for the subsequent studies of transportation of drugs.Based on BCS researches,CMMBCS can not only obtain the trend and advantages of single-component' BCS classification in multi-component environment,but also can gain the CMMBCS properties of Chinese medicines to illustrate the scientific nature of compound prescriptions.However,the human absorption prediction based on BCS concept and technology,although convenient,low-cost,and referential,should be classified as in vitro prediction since the lack of drug disposal parameters and the complex process of absorption,metabolism and transport in the body.The physiologically based pharmacokinetic(PBPK)models,simplifies complex process of drugs'ADME in human being to atrioventricular structures that based on physiological facts,should be classified as in vivo prediction,as the mathematical models composed of a series of physiologically significant tissue chambers which could simulate drug disposal in the body.The experimental data of BCS is also one of the core parameters of the establishment of PBPK model,PBPK models can predict all the key indicators of BCS and they differ in the basis for the classification of drug BCS attributes.Thus,it would be more realistic and effective to combine these two methods to predict the absorption of drugs in the human body from in vitro and in vivo and study the BCS classification of drugs.This study used baicalein as the research object.After model validation of single-pass intestinal perfusion methods and evaluating the applicability of aglycon components by SPIP,an essential technology of BCS permeability test,present study combined PBPK model and CMMBCS concept to predict intestinal absorption and BCS classification of baicalein,which can enrich CMMBCS.Methods:An analysis method for the content of markers,aglycons and baicalein were established.Fluorescein(FLU)and metoprolol(METO)were utilized as low/high-permeability class boundary standard to verify the applicability of the in situ perfusion model simultaneously.Literature survey of various permeability test methods and comparative analysis of SPIP,discussed the advantages and limitations of SPIP model.Methods of shake flask method in Chinese Pharmacopoeia,intrinsic dissolution rate(IDR),SPIPS and intestinal perfusion with venous sampling(IPVS)were used to determine BCS classification of baicalein and intestinal absorption mechanism.GastroPlusTM software's disposal model PBPK PlusTm module was used to establish and optimize the e in vivo PBPK model of baicalein in rats and beagle dogs,and the species was extrapolated to humans to predict the plasma concentration-time curve of baicalein in the adult population and the distribution of absorption in the gastrointestinal tract.Results:(1)Baicalein perfusate has good solubility,stability during the experimental period,and the material used in the experiment has no adsorption.Thus,the experimental results will not be interfered by these factors.(2)The effective permeability coefficient(Peff)values of metoprolol(METO)and fluorescein(FLU)were 5.42×10-5 cm/s and 0.19×10-5 cm/s,which means the model of SPIP was verified successfully.Through literature survey,SPIP model was proved more suitable for assessing the permeability of drugs.The Peff results of aglycones(Quercetin,Glycyrrhetinic acid,Formononetin,Genistein and Daidzein)were 2.89×10-5 cm/s,3.80×10-5 cm/s,2.56x10-5 cm/s,14.82×10-5 cm/s and 6.84×10-5 cm/s respectively,which refers that quercetin,glycyrrhetinic acid and formononetin are low permeability substances,while genistein and daidzein are high permeability substances.And the aglycones have the high correlation(r2=0.8528)between Fa predicted using Peff results from rats and Fa predicted by GastroPlusTM v9.0.Thus,selecting the rat jejunum as an intestinal absorption vector is a good choice for drugs with good absorption properties,and the use of SPIP in rats was found to be applicable in investigating herbal ingredients absorption and indirectly predicting fraction absorbed and permeability in humans.(3)The results of IDR(0.0157 mg/min/cm2)and the Peff values of main absorptive segments duodenum,jejunum and ileum(>5×10-5 cm/s)could classify baicalein as class II drug of the BCS.The PBPK model predicted the key indicators of BCS(dose number,absorption number and dissolution number),which could classify it to BCS-II again.The results of IP VS Pblood was 0.002×10-5 cm/s,which is much lower than the Peff value(6.39×10-5 cm/s)obtained,indicating that baicalein has intestinal metabolism and other behaviors.The Cmax and AUC predicted by the PBPK model are within two times of the error of the measured results,so the model can provide better prediction of absorption of baicalein in rats,beagle dogs and humans.The regional absorption fraction predicted by GastroPlusTM suggested that the majority of baicalein was absorbed in the duodenum and jejunum to be 117.5%,115.0%and 129.9%in rat,beagle dog and human,respectively.Surprisingly,the net%absorded to be above 100%when the simulation ends.And baicalein was absorbed in the ileum in human resulted in 38.7%.(4)The calculated D0 of baicalein in the compound prescription was less than 0.013,so it is classified as high solubility drug.While according to the same algorithm,the D0 range of the single baicalein was between 0.210 and 0.077,still less than 1,which is contrary to the low solubility result of the baicalein in IDR experiment and PBPK model.It is inferred that human dose of baicalein M0 calculated from classic prescription is too low,and this phenomenon can provide reference for determination of the best human oral dose of baicalein.Additionally,the Petr values of baicalein in high,medium and low concentration compound prescription were 13.94×10-5 cm/s,10.08×10-5 cm/s and 7.41×10-5 cm/s,and the results have been improved compared with the corresponding single components,which is still classified as high permeability.Conclusion:SPIP model in rats is a good method in investigating herbal ingredients absorption and indirectly predicting fraction absorbed and permeability in humans.The permeability results of intestinal segments gradually decreased from duodenum to colon,and the rate and extent of absorption of intestinal regions were determined:duodenum>jejunum>ileum>colon,and the absorption of baicalein in different intestinal areas might exhibit passive transport mechanism and extensive metabolism.Quite low amount of baicalein was discovered in the mesenteric blood,which suggested that comprehensive glucuronidation might occur in intestinal segments during the absorption process of baicalein.The combination of baicalein BCS properties and GastroPlusTM software can successfully predict the plasma concentration-time curve of baicalein in the adult population and its absorption distribution in the gastrointestinal tract.Additionally,PBPK models could establish in vitro and in vivo relevance and provide an excellent prediction for BCS class ? drug.The single baicalein is classified as BCS-II drug by BCS methods and PBPK models.And it may belong to CMMBCS-I in the GegenQilian complex environment.