Study On Quality Standard And Structural Modification Of Schizonepetin

Quality standard is crucial for innovation of pharmaceutical agents in different stages of drugdevelopment.To assure the quality of drugs,impurities must be monitored carefully.It is important to understand what constitutes an impurity and to identify potential sources of such impurities.Selective analytical methods need to be developed to monitor them.It is generally desirable to profile impurities to provide a yardstick for comparative purposes.New impurities may be observed as changes are made in the synthesis,formulation,or production procedures,albeit for improving them.At times it is necessary to isolate and characterize an impurity when hyphenated methods do not yield the structure or when confirmation is necessary with an authentic material.Availability of an authentic material can also allow toxicological studies and provide a standard for routine monitoring of the drug product.Schizonepetin,a new natural monoterpene,was first isolated from the essential oil of Schizonepeta tenuifolia in our laboratory in 1998.It had been reported to have antiviral,anti-inflammatoryk,analgesic,antipyretic and analgesic activities.Based on wide application and pharmacological research,the acute,subacute and genetic toxicity of schizonepetin was investigated.And we also studied the pharmacokinetic pro files of schizonepetin after oral and intravenous administrations in rats.However,no information is available in the literature on the quality standard for schizonepetin.This dissertation is divided five major chapters.The first part was a detailed review about the recent technique which was applied for determination of drug impurities.The second chapter gave a detailed study on the quality standards of schizonepetin.The solubility,the hygroscopicity,the loss on drying and the melting point were investigated to provide evidences for the establishing of the quality standard.The accelerated testing and the long-term testing were carried out to determine the period of validity.In the third chapter,three unknown related impurities were observed in analysis of schizonepetin bulk drug.A semi-preparative liquid chromatography was used for isolation of the three impurities.Based on MS and nuclear magnetic resonance(NMR)spectra,they were characterized as(-)-Mintlactone(Impurity I),(R)-(+)-Pule gone(Impurity ?)and(+)-Menthofuran(Impurity ?)respectively.A possible biosynthetic pathway of the three impurities was proposed and will likely contribute to the prediction of their toxicity.Moreover,a reversed-phase liquid chromatography method was developed for quantification of both the major impurities and the main constituent.The chromatographic separation was achieved on a Kromasill C-18 column(200 mm×4.6 mm,5?m.Jiangsu Hanbon,China).Methanol—water(68:32,v/v)was used as mobile phase.Flow rate was 1.0 ml/min and the column temperature was 30?.The injection volume was 10?L.The proposed method was validated and applied during impurity studies and quality control analysis of the bulk drug.In the fourth chapter,the structural modification of schizonepetin was studied.The water soluble functional group was introduced to schizonepetin,and several water soluble derivatives were synthesized.In the last chaper,we tested the antiviral activities against H3N2 and HSV-1 in vitro of target compounds.