Synthesis,biological Evaluation And Structure-Activity Relationship Study Of Camptothecin Analogues

Camptothecin is a kind of alkaloid containing five membered ring structure isolated from Chinese endemic plant Camptotheca acuminate,which has very remarkable antitumor activity and was concerned by people.In addition,camptothecin also has more obvious antifeedant,stomach poison,contact toxicityand other insecticidal activities and has the potential of developing new bio-pesticides.In this paper,7-ammonia methyl camptothecin derivatives wereused astrial reagents,its antiproliferative activitiesonSf9 cell were determined by MTT assay,and the structure-activity relationship were expounded by molecular docking method.Accordingly,we designed and synthesized a series of 7-amide camptothecinderivatives,and testedits cytotoxicity.In order to expound its structure-activity relationship,and to explore the mechanism,weused DS 2017 to build 3D-QSAR model.The specific research results are as follows.1.Antiproliferative activities of 7-methyl camptothecin derivatives and its molecular docking analysis.The parent drug CPT has demonstrated strong cytotoxicity to Sf9 cell line after 24h,the IC₅₀ was 6.6?mol/L.Compared with CPT,compounds A,1d,1f and 1i were showed stronger cytotoxicity,the IC₅₀were less than 1?mol/L,between 0.21 with 0.77?mol/L.Compounds 1a,1c and 1g were also exhibited better cellular toxicity,their IC₅₀were around 2?mol/L.In addition,compounds B,1b and 1hwere also exhibited cellular toxicity commensurate with CPT,its IC₅₀were 5.06⁹.57?mol/L.However,compounds C,1e and 2awere showed weakly activity,the value of inhibitory activity were around 20?mol/L,and other compounds?2b²e and 3a³c?were exhibited bad antiproliferative activities,the IC₅₀were greater than 30?mol/L.Subsequently,the molecular docking analysis results showed that two nitrogen-atomsof the urea-based/thiourea-based of7-ammonia methyl camptothecin derivatives were easy to form hydrogen bonds with amino acids Asn518,which had an important effect on stabilizing their ternary complexes.The fluorine atom of the compound 1f bond with the amino acid Lys915 and Asn886 to form hydrogen bonds,and other compounds containing halogen atoms substituted such as 1e,1g and 1h were not formed this interaction,indicating that the interaction has a certain role in improving its bioactivity.In addition,the volume of substituted in compounds 3a^cis too large to affect its cytotoxicity by combining with DNA-TOP 1 complexes.2.Antiproliferative activitiesof 7-amide camptothecin derivatives and its structure-activity relationship analysis.The Camptothecin?CPT?has a strong inhibitory effect on Sf9 cells,and its IC₅₀ was29.47?mol/L.After the introduction of carboxyl,the activity has a certain increase,and the IC₅₀ was 14.32?mol/L.Subsequently,most of compoundsafter introducing amino amide formation can significantly inhibit cell proliferation,in which the compound 4o is the best and its IC₅₀showed 1.71?mol/L.All of compounds 4b^j and 4n^v are exhibited significant cellular activity,which were less than7?mol/L.In addition,compound 4kwas also showed considerable cytotoxicity with camptothecin,the IC₅₀was 23.79?mol/L;and compound 4a,4w,4l and 4m were showed weak cytotoxicity,the IC₅₀were greater than 58?mol/L,especially the compound 4a and the IC₅₀ was reached to 292.2?mol/L.3D-QSAR results showed that the correlation coefficient r² of the predicted and the actual activity of the training set in the constructed QSAR model was reached 0.946.Accordingly,the R² of the test set was also reached 0.925,which was showed that the model had good activity prediction function.The electrostatic potential grids analysis showed that 7-bit substitution of camptothecin derivatives,the stronger the negative side of the left group was beneficial to the activity.The weaker the right group negatively may be more advantageous to the activity.In addition,the results of Van der Waals grids showed that the 7-bit substituted group size cannot be too large,otherwise unfavorable to its activity.The molecular docking results showed that the hydroxyl group on the carboxyl group in compound 3 would be formed hydrogen bonds with TGP941,and the H atoms on the amide in 7-amide camptothecin derivatives would be formed hydrogen bonds with TGP941.Whereas the substitution of dimethyl amine in compound 4b leads to the loss of H atom,resulting in a sharp decline in its activity.In compounds 4f^j,7-?4-fluoro-benzyl amide?-Camptothecin showed the best activity,and the fluorine atom on the benzene ring would be formed hydrogen bonds interacting with Lys602,while the benzene ring and Pro597 formed Pi-Alkyl interactions.The chlorine atom has not formed hydrogen bonds with amino acids,and the hydrogen bonds was formed in the compound 4h with Tyr592 have a certain effect on the stabilizing top 1-DNA complexes.Obvious the stuction of Compounds 4k-n,the Oxygen atom on the morpholine ring in compound 4n would found a hydrogen bonds interaction with Lys602.After the introduction of amino acid ester groups,most compounds can found hydrogen bonding with DN A or Asn518.In addition,the introduction of large group Benzyl on the side chain of amino acid methyl ester in compound 4w can cause its activity to decrease,the reason would be that the space of large groups is larger,and the oxygen atoms on the ester bonds can not form hydrogen bonds with amino acids on top 1 and thus lead to decreas activity.