| Cholic acid(CA)is a kind of steroids existing in the bile of human and vertebrates.CA is not only the raw material for the preparation of bezoar drugs but also it is used to synthesis chenodeoxycholic acid(CDCA),which is the medicine for treatment of hepatobiliary drugs.Due to the lack of recognition and attention to animal drugs and bile in China,the vast majority of animal bile is wasted.The output of CA at home and abroad is generally insufficient,but the demand is strong.The domestic export quantity of CA is increasing year by year and the market price is higher.At present,the process of synthesizing CDCA from CA is still deficient in industrial application.In order to find a more suitable production process for industrialization,this paper carried out a study on the process of extracting CA from ox-gall cream and synthesizing CDCA with CA as raw material.The specific work and experimental results are as follows:1.Extraction of CA from ox-gall cream by crystallization method.Five factors affecting the extraction rate of CA were studied by experiments including the type of extraction solvent,the liquid-solid ratio of ethanol to ox-gall cream,the feed ratio of ox-gall cream to hydrogen peroxide,the extraction time and the concentration liquid-solid ratio.From the single factor experiment and response surface experiment,when the extraction solvent was anhydrous ethanol,the liquid-solid ratio was 6:1(mL/g),the feed ratio was 0.75:1(g/mL),the extraction time was 1 h,and the concentration liquid-solid ratio was 3.5:1(mL/g),the extraction rate of CA was 80.2%.2.Purification of crude CA.CA was purified by recrystallization method.The effects of four factors,such as solvent type,solvent dosage,reflux time and crystallization temperature on the recrystallization efficiency of CA were studied by single factor experiment.The optimal purification conditions were obtained as follows:absolute ethanol as solvent,liquid-solid ratio of 10:1(mL/g),reflux time of 1 h,recrystallization temperature of 0℃,under which the comprehensive value of CA purification was 92.5%.3.Synthesis of CDCA with CA as raw material.Using NBS as oxidant,the sequence of oxidation reaction of three hydroxyl groups on cholesteric skeleton was determined as C7-OH>C3-OH>C12-OH.CDCA was synthesized by the following four steps:a.Esterification to protect carboxyl;b.Selective acylation of hydroxyl groups on C3 and C7;c.NBS to oxidize the hydroxyl group of C12 to carbonyl;d.Removal of ketone group at C12 position by Huang-Minlon method and removal of protective group by hydrolysis to obtain CDCA.In the esterification reaction,the effects of different kinds of catalyst,the ratio of CA to PTS and reaction time on the yield were studied.The optimum conditions were as follows:PTS as catalyst,the ratio was 1:0.05(g/g),reaction time was 4 h,yield was 97.8%.In the acylation reaction,the effect of protective group type,feeding ratio of methyl cholic acid to protective group and reaction time on the product was studied.The optimum conditions were as follows:acetic anhydride as protecting group,feed ratio was 1:1.5(g/g),reaction time was 8 h,yield was 92.4%.In the NBS oxidation reaction,the effects of the ratio of water to acetone and the reaction time on the yield were studied.The optimal conditions were as follows:the ratio of water to acetone was 1:3(mL/mL),the reaction time was 3 h,and the yield was 89.1%.The effects of the ratio of sodium hydroxide to hydrazine hydrate and the ratio of solid to liquid on the yield were studied in the alkaline hydrolysis and reduction reactions.The optimum conditions were as follows:the ratio of sodium hydroxide to hydrazine hydrate was 1:3(g/g),the ratio of solid to liquid was 1:15(g/mL),and the yield was 87.3%.4.The products were characterized by IR and 1HNMR.The purity of CA and CDCA were 97.1%and 96.8%respectively by HPLC. |
PDF Full Text Request