Preparation And Evaluation Of Bufadienolides-loaded Solid Dispersion Pellets

Toad venom,a traditional Chinese medicine,has been widely used in China as a cardiotic,blood pressure stimulating,anodyne,antineoplastic,and antimicrobial agent for thousands of years.The major biologically active constituents of toad venom are bufadienolides,principally bufalin(B),cinobufagin(C),and resibufogenin(R),which all have the characteristics of strong biological activity,high efficiency and low toxicity.In current,commercially marketable products of bufadienolides are prepared only from raw materials or a single active ingredient with a very low purity,consequently producing a variety of adverse reactions and poor efficacy.Additionally,bufadienolides were shown to be poorly water-soluble and exhibit acid instability,which makes the formulation of bufadienolides rather challenging.Therefore,the aim of this study is to isolate and obtain the high purity mixture and then loaded BUs into solid dispersion to ensure both high solubility and stability of the drug.Firstly,the thin layer chromatography(TLC)and high-performance liquid chromatography(HPLC)methods were developed to assay raw material and the final separated products in qualitatively and quantitatively,respectively.The raw material were separated by ethanol(80%)reflux extraction,ethyl acetate extraction and loaded on silica gel column chromatography separation with the content and the transfer rate of bufadienolides as response.The final separated products contained mainly B,C and R(purity ? 93%)with a transfer rate above 80%.Preformulation study showed that the solubilities of bufadienolides in water were very low and its' stability are poor.Spray congealing(SC)was employed to prepare BUs-loaded solid dispersion.The optimized carrier was F127 and theoretical drug loading was 10%(w/w).The SD was evaluated in term of SEM,XRD,DSC,FTIR and dissolution.It was found that all drugs were molecularly dispersed within matrix and had a significant enhancement(~4-fold higher)of dissolution rate.Furthermore,synchronized release(?2?50)of different drugs from a single carrier was achieved due to the the highly molecular dispersibility and the excellent solubilisation properties of F127.SEM revealed that SD was generally spherical,discrete and of smooth surface appearance.In addition,the physical stability of SD exposed to different temperature and relative humidity were evaluated with DSC,XRD,FTIR and dissolution,it was found that the SD was physically stable for at least 4 weeks at controlled conditions.Bufadienolides enteric solid dispersions were prepared with Solventspray congealing technique using HPMC-AS as matrix.Dissolution study revealed that the D120 of each components is less than 7%.Stability test showed that the drug content and dissolution behavior has not changed under accelerated experiment condition for 4 weeks.In addition,the ability of HPMC AS to stabilize the supersaturated sate of BUs is good for the absorption in vivo.The BUs-loaded solid dispersion pellets were prepared by extrusionspheronization method.The process parameters were optimized with the yield,brittleness and sphericity as response.The optimized preparation process is feasible and repeatable.A novel sensitive,accurate and reproducible HPLC/MS/MS method was developed to determine the three bufadienolides in rat plasma simultaneously.After oral administration,compared with bufadienolides aqueous solution(BU-S),the relative bioavailability of B and R were enhanced.In conclusion,BUs-loaded solid dispersion immediate release and enteric pellets with good physical stability were able to improve the in vitro dissolution behavior,presumably giving reliable scientific basis for the development of new formulation.