Design,synthesis And Biological Activity Of Novel Compounds With Synephrine As Nucleus

Synephrine is an alkaloid found in citrus plants in the rutaceae family.Its structure is similar to epinephrine and ephedrine and it similar biological activity.Synephrine is mainly expressed as an adrenergic alpha receptor stimulant,and also has a certain excitatory effect on the cardiac beta receptor,which can promote vasoconstriction,increase cardiac output,increase blood pressure,expand bronchial tubes and trachea;can promote metabolism and combustion fat,which has the effect on weight loss.In traditional Chinese medicine,synephrine is mainly used for the treatment of bronchial asthma and hypotension,collapse,shock,orthostatic hypotension,as well as the treatment of uneatable food,phlegm and stomach ptosis,etc.Also used to treat for various shocks,heart failure patients,and treatment of gastric and duodenal ulcers and other diseases;in the treatment of moderate and mild depression,blood sugar regulation,etc.,Synephrine has also achieved good results.Due to toxic and side effects,ephedrine has been banned in some countries in recent years,but synephrine has little side effects and can be used as a substitute for ephedrine,so the market prospects are promising.Limited by the low extraction efficiency of synephrine and the complex and difficult control sites,the current researches on synephrine are mainly based on chemical synthesis methods,improvement of extraction methods and analysis and testing.There are few studies on synthesis of synphrine derivatives and biological activity,which affects the development prospects of synephrine.As a large citrus producing country,China produces more than 10 million tons of citrus peel residue each year and contains more than 55,000 tons of synephrine,but most of the resources are wasted,so research and development of derivatives and their derivatives using synephrine as the core biological activity have important theoretical significance and significant economic value.1.Design and Theoretical Calculation of Targets with SynephrineThis topic is based on the design concept of multi-target drugs,using synephrine as the core,and designing connected multi-target drugs through the coupling pharmacophore method.Based on the laboratory’s many years of experience in medicinal chemistry,highly active pharmacophores are used as linking fragments,such as azole-containing fragments,sulfonamide groups or marketed drugs fluoroquinolones（FQs）,dihydroartemisinin（DHA）fragments,etc.Using drug design theoretical design of the connection structure,the reasonable derivation of the core structure of synephrine,to obtain the molecular structure type of this study.Based on the characteristics of amino groups,alcoholic hydroxyl groups and phenolic hydroxyl groups,on the basis of preliminary experiments,a method for introducing high-yield,highly selective active fragments at the reaction site of synephrine was found,and then 10 new designs of synephrine were developed derivative.Through the calculation of physical parameters,some target molecules are eliminated,and the final target molecules are selected.2.Synthesis of target compoundsIn view of the structure of the target compound,multiple synthetic routes were designed;starting with synephrine,starting from the amino group,and then using the difference between the alcohol hydroxyl group and the phenolic hydroxyl group,using different synthesis conditions and other fragments to link;or using the amino group the modified synephrine is fragment-coupled with other fragment intermediates.Through exploration of experimental conditions,combined with column chromatography and thin plate chromatography,10 series and 106 target compounds were finally synthesized;the structures of the synthesized target compounds were confirmed by ¹HNMR,¹³CNMR and HRMS.3.Test and result of target compound biological activityThere are few derivatives of synephrine,and its biological activity is difficult to predict.In order to grasp the possible activity of the molecule,the author introduced azole ring,dihydroartemisinin,and fluoroquinolone structures into the target molecule.Therefore,priority is given to the antibacterial activity test of the target molecule,and six sensitive pathogenic strains and the fungus Pichia Pastoris are selected.Subsequently,their inhibitory activity against Mycobacterium smegmatis and two types of tumor cells were measured to study the anti-tuberculosis ability and anti-cancer activity of the target molecule,and then to investigate the multi-target properties of the hybrid molecule.Anti-sensitive strain activity:Six common strains belonging to Gram-positive and negative bacteria were selected for the activity test.The test results show that,in addition to its weak ability to inhibit acinetobacter baumannii,the target compounds also shows good antibacterial activity against the other five strains.For Staphylococcus aureus,the MIC values of compounds TM8-1,TM8-3,TM8-4,TM9-15,TM9-17reached 0.2μg/m L,and the activity was stronger than the antibacterial drugs vancomycin,cephalosporin,chlorine amycin,florfenicol,lomefloxacin,enoxacin,ciprofloxacin,norfloxacin;the MIC values of compounds TM2-6 and TM4-3 against E.coli were 0.4μg/m L and 0.8μg/m L,surpassing the marketed antibacterial drugs vancomycin,ampicillin,florfenicol,chloramphenicol;the optimal MIC value for the other three strains is 1.6μg/m L,which is still a certain gap from the positive control,indicating that such the molecule has a certain selectivity for different bacteria（Figure3）.The structure-activity relationship analysis found that the antibacterial activity of the compound was not only related to the structure of the active fragment,but also to the type and length of linker.The effects of different linkers on antibacterial activity are:pyrimidine linker>2-C linker>4-C linker.Compared with active fragments,the antibacterial activity of molecules containing FQs fragments is superior to other active fragments.Among them,the corresponding molecules of gatifloxacin,clinfloxacin,sarafloxacin and ciprofloxacin fragments have better antibacterial activity.We also found that the amino protecting group on synephrine also has an effect on antibacterial activity and broad-spectrum antibacterial activity.When there is no protecting group or acetyl group,the antibacterial activity is better.These results indicate for the first time that synephrine derivatives have antibacterial activity.Anti-mycobacterium smegmatis activity:This activity test was completed at the Institute of Modern Biomedicine,School of Student Science,Southwest University.The measurement results of the activity against Mycobacterium smegmatis show that the target molecule TM2-4 is the molecule with the best activity among the tested molecules,and the MIC value is as low as 0.097μg/m L,which is stronger than the 12listed control drugs.The MIC values of compounds TM2-1,TM2-5,TM4-1,TM4-3,TM4-4,TM8-4 are all less than 0.8μg/m L,which has the value of further research.Molecular structure-activity relationship analysis found that the molecular activity of FQs fragments was stronger than that of DHA,azoles and sulfonyl fragments,and the activities of ciprofloxacin,clinfloxacin and gatifloxacin in FQs fragments were relatively stronger;for linker,flexible aliphatic chain hydrocarbon linker is stronger than rigid pyrimidine ring linker,2-C linker with smaller molecular weight and shorter chain is stronger than 4-C linker.This study found for the first time that some molecules derived from synephrine show strong anti-tuberculosis ability and have the potential for further development.Antifungal activity:The target compounds and some intermediates were tested against Pichia pastoris.Molecules containing azole fragments or FQs fragments basically exhibit antibacterial activity at a concentration of 0.256 mg/m L,and most molecules have MIC values ranging from 0.064 to 0.256 mg/m L.Although the antifungal activity of the tested compounds did not exceed the positive control drug fluconazole（MIC=0.032 mg/m L）,but under the premise that most of the molecular weights increased,there was not much difference from fluconazole activity.Such molecules still have the prospect of further restructuring and modification.This study also found for the first time that synephrine derivatives have antifungal activity.Anti-cancer activity:Some target compounds and some intermediates were tested for anti-cancer activity at the New Drug Creation Center of Chongqing University of Arts and Sciences.The results showed that the tested molecules did not show high activity against the tested cancer cells.Antiulcer activity of citrus:Some compounds were tested for the inhibitory activities of Colletotrichum gloeosporioides Co.3,Alternaria alternata Al.6,and citrus ulcerative pathogen at citrus research institute,Southwest University.The results showed that the tested molecules showed certain inhibitory activity against Colletotrichum gloeosporioides Co.3.There were four target compounds that had an inhibition rate of more than 40%at 4μg/m L.Among them,compounds TM3-12 and TM3-15 showed good inhibitory activity against Alternaria alternata Al.6,which was close to the positive control imidine.But they did not show high activity to citrus ulcer pathogen.This topic is the first to synthesize a part of synephrine derivatives.There are 10series and 106 target compounds,all of which are new compounds.At the tested concentration,some molecules showed very good antibacterial activity,and some molecules were stronger than the marketed fluoroquinolone drugs.Most of the molecules showed certain antibacterial activity against Pichia pastoris,but did not surpass the marketed drug fluconazole.In the determination of anti-mycobacterium smegmatis,the molecules containing fluoroquinolone fragments showed higher activity,and some of them had inhibitory activity much stronger than the first-line antituberculosis drugs rifampicin and isoniazid.The target molecule’s weaker ability to inhibit cancer cells also indicates that such molecules are selective.The physical parameters of all the synthesized target molecules were calculated,except for the molecular weight,which basically conformed to the five principles of drug design.Therefore,the highly active molecules obtained in this study can be used as lead molecules for further research.This subject is the preliminary attempt of the laboratory to conduct molecular hybridization of the active fragments and pharmacodynamic fragments FQs,DHA,azoles and aromatic sulfonamides based on the idea of drug hybridization.The activity measurement shows that some molecules are stronger than monomer molecules,and the ability of synergistic synergistic effect of the medicinal fragments is achieved.Therefore,the research results have not only found highly active molecules that can be further studied,but also verified the design ideas of the molecules,broadened the synthetic route,new activity and structure-activity relationship of the synephrine derivatives.It has laid a good foundation for the subsequent design and research of synephrine derivatives.Other molecular activities designed on this theme are still under study.