Study On The Factors Affecting The Cyclization Of Catecholamines During Electrochemical Oxidation

In recent decades,researchers at home and abroad have been increasingly interested in the study of catecholamines.The reason is that catecholamines,as a kind of very important neurotransmitters in human body,play a pivotal role in the normal operation of the body.It is composed of catecholamine nucleus(benzene ring with two ortho-hydroxyl groups)and a side chain amino group.Catecholamine substances mainly include dopamine(DA),L-DOPA(L-Dopa),epinephrine(AD or E),norepinephrine(NA or NE)and related derivatives and other bioactive substances.Catecholamine in the human body mainly acts as the role of nerve substances,mainly plays the role of regulating physiological functions and transmitting physiological signals.Many studies have shown that the increasing incidence of Parkinson’s disease is closely related to the level of dopamine neurotransmitters in the body.The main pathogenic cause of Parkinson’s disease is the deformational death of dopaminergic neurons,which is mainly related to the formation of neuromelanin.In human body,dopamine will undergo oxidative cyclization reaction to form 5,6-dihydroxyindole,and then undergo oxidative polymerization and other reactions to form neuromelanin.Therefore,in-depth research on the cyclization reaction of catecholamines is conducive to revealing the formation mechanism of neuromelanin and thus contributing to the pathogenesis of Parkinson’s disease.It is also of great significance for its follow-up treatment and prevention.At present,many scholars have adopted spectral and chromatographic methods to study catecholamine.However,because the absorption wavelength of catecholamine and cyclization products will appear in different bands,it is not conducive to the development of related studies.All catecholamines have electrochemical activity,and the corresponding cyclization products also have electrochemical activity.Therefore,electrochemical method is very efficient and easy to operate.To sum up,this study focuses on using cyclic voltammetry technology to study the behavior of catecholamine and three catecholamines.By setting different pH conditions,it was observed that the peak current of cyclization peak was larger under neutral and alkaline conditions,that is,a larger pH was more conducive to the occurrence of cyclization reaction,because at this time,it was more conducive to the deprotonation of the amino group of the side chain of obenzoquinone.After that,the concentration of buffer was changed,and it was found that the strong buffer capacity of buffer would promote cyclization.Buffering capacity had the greatest effect on epinephrine of the three catecholamines.According to the conclusion,the cyclization can be affected by controlling the buffer substances in vivo,and then affect the synthesis of neuromelanin,so as to provide guidance for the prevention and treatment of Parkinson’s disease.In addition,the scanning speed during the experiment will also affect the degree of cyclization.When the scanning speed is high,the cyclization time is short,which is not conducive to cyclization.Therefore,we should pay more attention to the influence of sweep speed on the results of cyclic voltammetry in the future.At the same time,in view of the influence of sweep speed,experimental conditions can be flexibly changed to achieve the control of experimental results.In addition to the above factors,some physiologically active substances also affect the degree of cyclization of catecholamines.Like cysteine and ascorbic acid.It was observed that the original cyclization peak decreased with the addition of cysteine and ascorbic acid.Although the presence of both substances inhibits cyclization,they intervene and affect the cyclization process through two different mechanisms.Cysteine acts as a nucleophile to attack the quinones containing electron-deficient rings,and thus the intermolecular nucleophilic addition occurs.This reaction competes with the intramolecular cyclization reaction,so the cyclization reaction is inhibited to some extent.Ascorbic acid,on the other hand,is reductive,and its reduction potential is lower than that of quinone,so it can reduce the corresponding quinone,so the cyclization reactants are consumed,and the cyclization reaction cannot be carried out.In summary,the influence mechanism of different factors on cyclization reaction was explored through a series of experiments.The above conclusions can provide guidance for the synthesis of neuromelanin and provide basis for the prevention and treatment of neurodegenerative diseases in the future.