Synthesis Of Lipo-Aconitine Derivatives And Its Structure-Effect On Toxicity To Breast Cancer Cells

Diterpene alkaloids are a class of natural products with significant chemical properties and biological activity,which are mainly distributed in plants of the genus Aconitium,Delphinium and Spirea.Modern pharmacological studies have found that such alkaloids have a wide range of physiological activities such as anti-inflammatory,analgesic,anti-arrhythmic,and anti-tumor.Aconitine,as one of the oldest toxic components in nature,has gradually attracted much attention,for its significant anti-tumor activity than other C₁₉-diterpene alkaloids,as well as its reversal effect on multidrug resistance tumor cells.However,as the main toxic component from the Chinese herbal medicine Aconitum,aconitine has obvious toxicity on the nervous system,circulatory system,digestive system,etc.Thus,its clinical application is limited.It has very important theoretical value and practical significance to improve its anti-tumor activity while reducing toxicity,and enhancing the targeting for tumor tissue.Based on our previous research,in order to investigate the effect of group diversity-oriented synthesis on its anti-tumor activity,series of aconitine derivatives on C3,C8,C13,C14,C15,N atoms have been designed and synthesized,guiding by the results of molecular docking as well as the principle of minimum modification.Furthermore,the in vitro inhibitory activities on breast cancer cell line MCF-7 have been investigated.The main findings are as follows:1.21 compounds have been designed and docked.And the molecular docking find the N atom,C3 hydroxyl group,C13 hydroxyl group,C14 and C8 positions all contribute to the interaction with the receptor protein residues.2.Taking aconitine,meconeine,homoconeline,and chrysoconine A as raw materials,a total of 21 compounds were synthesized,which were a 3-acetylated derivative one 15-acetylated derivative,five 14-modified derivatives,five N-atom modified derivatives,three salts,and two other diterpene alkaloids.Except X16,all the derivatives were synthesized for the first time,and none of them have been reported in the literature.3.The results of in vitro cytotoxicity tests found that 13 of the 21 compounds（X2-6,X9,X11,X13,X16-19,X21）showed good anti-proliferative activities on the breast cancer cells(IC₅₀<20μM),about 4.5-1.1 times stronger than the positive drug Etoposide.Compared with the lead compound 19,the five compounds X4-5,X9,X16 and X18 have increased anti-proliferative activity than 19.Among them,the IC₅₀ value of X4（8-（9,13-difluorooctadecanoyl）oxy）-aconitine),X9（15-acetyl-14-（4′-OCH₃）-benzoyl-8-linoleate aconitine）,X16（8-linoleate mesaconitine）reached 4.00±0.3μM,6.21±0.14μM,6.17±0.19μM,respectively,showing excellent tumor cell proliferation inhibition active.The most active compound 4(IC₅₀=4.00±0.3μM),is slightly lower than Adriamycin(IC₅₀=1.22±0.43μM),but about 4.5 times stronger than Etoposide(IC₅₀=18.01±1.64μM),which is expected to become a new antitumor candidate compound.4.The structure-activity relationship analysis shows that 3-OH,8-lipo,14-benzene ring and N atom in the aconitine molecular are the key factors to determine whether the aconitine long-chain fatty acid esters have antitumor activities,or not.On this basis,after the addition of the 8-position fatty acid halogen,the fluorine atom will increase the antitumor activity,but the introduction of bromine atom reduces the activity,and the double substitution of halogen is better than the single substitution;the introduction of electron-donating groups on the 14-benzene ring has conducive to the enhancement of activity;the presence of 13-OH and 15-OH is not the key to whether the compounds have anti-tumor activity,but the presence of 15-OH is conducive to the maintenance of activity,acetylation or lack of 13-OH will lead to decreased cytotoxicity.In addition,the hydrochloride salts can enhance its solubility,greatly improving its activity.In conclusion,the anti-tumor structure-activity relationship of long-chain fatty acid diterpene alkaloids esters have been laid a foundation.It is expected to search more lead compounds with high activity and low toxicity,as well as enriching the chemical research of diterpene alkaloid compounds.