Cis-trans Isomerization And Solubilization Of Trans-N-p-coumaroyltyramine

Trans-N-p-coumaroyltyramine(N-p-t-CT)which was firstly isolated from Dioscorea opposita.in our previous study,it has been attacted much attention due of its many biological activities such as antiviral,anti-inflammatory,anti-oxidation and ?-glucosidase inhibitory activity.Among them,?-glucosidase inhibitory activity is particularly significant.Further research has shown that it's poor water soluble and easy cis-trans isomerization which greatly reduces the inhibitory activity of ?-glucosidase.In this work,an HPLC method is established for the determination of N-p-t-CT in Dioscorea opposita Thunb,Later the cis-trans isomerization phenomenon was studied.Moreover,the water solubility of N-p-t-CT is increased by chemical modification and physical encapsulation.The main contents are as follows:1.Determination and cis-trans isomerization of N-p-t-CT in Dioscorea opposita ThunbAn HPLC method was established to study the effects of different drying methods on the content of N-p-t-CT in different parts of Dioscorea opposita Thunb(peeled rhizomatous tubers,peel).The results indicate that the content of N-p-t-CT in the peel is higher than that in the peeled rhizomatous tuber.The different dry methods have no obvious effect on the content of N-p-t-GT in samples.The N-p-t-CT in extract of Dioscorea opposita Thunb can occure cis-trans isomerization under light to generate the N-p-c-CT.2.Synthesis of N-p-t-CTChemical synthesis method was used for the preparation of N-p-t-CT.The p-hydroxycinnamic acid was prepared from 4-hydroxybenzaldehyde and propanedioic acid as a raw material.Then N-p-t-CT was prepared from p-hydroxycinnamic acid and 2-(4-hydroxyphenyl)ethylamine,and its purity was over 99%.The all compounds were characterized by UV-vis,HPLC,1H NMR and MS spectrum.3.Study on the cis-trans isomerization of N-p-t-CTHPLC method was established to separating N-p-t-CT and N-p-c-CT,The effects of light with different wavelength,solvent,temperature,concentration and pH value of the solution werel investigated on the cis-trans isomerization for N-p-t-CT.The results show that the UV light is the main factor to induce the cis-trans isomerization.With the decrease of solvent polarity,the degree of isomerization decreases.It was observed that,the degree of isomerization decreases with the increas of concentration and pH value.At the same time temperature has no effect on isomerization.It was revealed that,N-p-t-CT is relatively stable under the conditions without illuminate,in small polar and alkaline solvents with high concentration.4.Study on the solubilization of N-p-t-CTPolyethylene glycol mPEG4OO was added to the 4'-hydroxyl group of N-p-t-CT to increase its water solubility through chemical modification.Firstly,mPEGylated sulfonic acid esterification reacts with 2-(4-hydroxyphenyl)ethylamine modified by di-tert-butyl dicarbonate(BOC).Then,trifluoroacetic acid was used for deamination to produce mPEGylated hydroxyphenyl ethylamine.At last,mPEGylated hydroxyphenyl ethylamine reacts with p-hydroxycinnamic acid and mPEGylated N-p-t-CT was obtained.The water solubility of N-p-t-CT increases 238 times due to the introduction of mPEG400.N-p-t-CT/Hp-?-CD inclusion complex was prepared by freeze drying method.The drug loading was 2.8%and encapsulation efficiency was 18.2%.The inclusion complex was characterized by UV-vis,IR,XRD and1HNMR.The water solubility of N-p-t-CT increases 1641 times due to the formation of inclusion complex.The inhibitory activity of a-glucosidase showed that the IC50 values before and after inclusion were 1.72±0.2 and 2.73±0.2 ?M,respectively.The formation of inclusion complex can increase the water solubility of N-p-t-CT and simultaneously inhibit the activity of ?-glucosidase.