Design And Synthesis Of Tetrahydro-β-carboline Analogues In Food And Their In Vitro Antitumor Activity

Tetrahydro-β-carboline compounds are indole alkaloids widely found in nature,mainly in plants and marine organisms,but also widely distributed in foodstuffs,such as chocolate,cocoa beans,maca,sweet potato,black garlic,codonopsis fruits and fruit derivatives.However,the low content and difficulty in purification of this class of compounds isolated from foodstuffs have limited their applications in food,chemical products and pharmaceuticals.The tetrahydro-β-carboline parent nucleus is the basic parent nucleus showing biological activities,and this class of compounds has a variety of biological activities,including antitumor,antibacterial,antiviral,antioxidant activities and anti-hypertensive activities.Therefore,the chemical synthesis and biological activities of tetrahydro-β-carboline analogs have attracted much attention from researchers.The methods for the synthesis of tetrahydro-β-carboline analogues are becoming more and more sophisticated.In this study,tetrahydro-β-carboline compounds were designed,synthesized and investigated for their antitumor activity based on their physiological activity and"advantageous structure".Based on the structural characteristics of the compounds and the available literature,the possible targets of their antitumor activity were speculated and preliminary molecular docking simulations were performed.This study will provide a scientific basis for the research and application of tetrahydro-β-carboline compounds in food.In this study,the construction of tetrahydro-β-carboline parent nuclei in compou nds was accomplished by Pictet-Spengler cyclization reaction.Firstly,two tetrahydro-β-carboline intermediates were synthesized by Pictet-Spengler cyclization reaction us ing tryptamine hydrochloride（5-methoxytryptamine hydrochloride）and ethyl pyruvate as raw materials,and then by two different synthetic routes.Structural modificatio ns were performed on these 2 intermediates,and then 36 compounds were synthesi zed.The target compounds were structurally characterized by NMR hydrogen spectr oscopy,carbon spectroscopy and mass spectrometry.In summary,in this study,two intermediates and 34 target compounds were synthesized by chemical synthesis,of which 33 compounds were not reported.The anti-tumor activity of 36 target compounds was tested by MTT method,and the activity was screened by using human lung cancer cells A549,human liver cancer cells He PG2,human colon cancer cells HCT116,cervical cancer Hela cells,and breast cancer MDA-MB-231 cells.The results showed that most of the compounds were cytotoxic to all five tumor cells,and nine of them inhibited tumor cells by more than 50%at a drug concentration of 40μM;these nine compounds were subjected to concentration gradient re-screening,the half-inhibitory concentrations(i.e.IC₅₀ values)of compound Z3 on lung cancer A549 cells,liver cancer He PG2 cells,colon cancer HCT116 cells and breast cancer MDA-MB-321 cells were 25.59μM,23.85μM,21.66μM and 13.35μM,respectively;the IC₅₀values of compound Z7 on lung cancer A549 cells,colon cancer HCT116 cells and breast cancer MDA-MB-321 cells were 5.43μM,31.40μM and 16.79μM,respectively;the IC₅₀ values of compound Z10 for lung cancer A549 cells were 11.57μM;the IC₅₀value of compound Z11 for breast cancer MDA-MB-321 cells was 28.63μM;the IC₅₀ values of compound Z15 for lung cancer A549 cells,colon cancer HCT116 cells and breast cancer MDA-MB-321 cells were 6.58μM,24.05μM and 23.62μM;the IC₅₀values of compound Z18 were 13.22μM for lung cancer A549 cells and 9.80μM for compound Z21;the IC₅₀values of compound Z27 for lung cancer A549 cells,liver cancer He PG2 cells and breast cancer MDA-MB-321 cells were 25.94μM,22.56μM,and 35.65μM;the IC₅₀values of compound Z28 were 18.24μM,38.99μM,and 39.78μM for lung cancer A549 cells,liver cancer He PG2 cells,and breast cancer MDA-MB-321 cells.Among them,compound Z7showed the best antitumor activity against A549 cells.The six compounds with relatively good antitumor activity obtained from the screening were subjected to molecular docking simulations,and the results showed that the six compounds Z3,Z7,Z10,Z15,Z18 and Z21 could enter the active pocket of kinesin Eg5（Eg5 protein is highly expressed in a variety of tumor cells and is closely related to tumorigenesis,development and prognosis）and form hydrophobic force interaction and hydrogen bonding with the major amino residues therein,and the binding to Eg5 protein is more stable.It is speculated that the antitumor activity of these tetrahydro-β-carboline compounds is related to the interaction of kinesin Eg5 in tumor cells.