Design, Synthesis And Antitumor Activities Of Artemisinin Derivatives

Artemisinin is isolated from Traditional Chinese Medicine Artemisia annua L,which contains a 1,2,4-trioxane moiety in its molecule,has become a potential lead compound in the development of antimalarial agent.Despite the clinical significance of artemisinin in treating malaria,numerous drawbacks,e.g.,poor solubility in water and oil,poor oral activity,and short plasma half life,have limited its usefulness.Attempts to develop highly effective antimalarial agents with less adverse reactions led to the synthesis of a large number of artemisinin derivatives,e.g.,artemether,arteether,and dihydroartemisinin（DHA）.In addition to its antimalarial activity,artemisinin had been reported to have cytotoxic effects against HL-60,P388 and MCF7 tumor cells,which would be a suitable leading compound for antitumor drugs.To improve the efficacy of artemisinin against tumor cell growth and investigate its antitumor mechanism in leukemia cells,DHA was taken as the leading compounds, structure modification was done,and eighty-five artemisinin derivatives were designed and synthesized.All the target compounds have never been reported in literatures.They were divided into four series according to their structures:artemisinin derivatives containing a substituted chalcone（Y-01-Y-33）,artemisinin derivatives containing a substituted dihydrochalcone or flavan（Y-34-Y-44）,artemisinin derivatives containing a substituted combretastatin A-4 analog（X-01 - X-18）,artemisinin derivatives containing a nitrogen-containing heterocyclic compound（L-01- L-23）,and the structures were confirmed by the application of ¹H-NMR,¹³C-NMR,IR and MS spectral data.Some characteristics about IR,¹H-NMR and ¹³C-NMR spectral data of the target compounds were summarized.In IR spectra,the character peak of 1,2,4-trioxane moiety was near 1028 cm^-1.In ¹H-NMR spectra,the stereochemistry of these compounds was determined by chemical shift of H-10 and coupling constant between H-9 and H-10.The DHA ethers are the P-isomer as indicated by a chemical shift（4.90 ppm） and a small coupling constant（J= 3.3 Hz）,while the DHA esters are theα-isomer（δ= 5.89 ppm and J = 9.9 Hz）.The geometrical configuration of chalcone and cinnamamide side chains is trans, which was determined by coupling constant betweenα-H andβ-H ofα,β-unsaturated ketones（J = 15.6 Hz）.The chemical shift of H-4 and H-9 was displayed at 2.36 ppm and 2.65 ppm for artemisinin,and protons at C₁₀ and C₁₂ of artemisinin appeared about 4.50-6.00 ppm.The ¹³C-NMR spectra of artemisinin derivatives indicated that the chemical shift of C-10,C-3,C-12 and C-12a was at about 104.1 ppm,102.2 ppm,87.9 ppm and 81.1 ppm respectively.The peaks of other carbon for artemisinin were at lower magnetic field, the 5 value was 55.0-10.0ppm.The antiproliferative effects of these artemisinin derivatives in human leukemia HL-60 cells were determined by direct cell counting,and all of these artemisinin derivatives showed preferable activity against HL-60 cells growth.Among them,compounds Y-01-Y-14,Y-17,Y-22-Y-26,Y-34-Y-40,Y-42-Y-44,X-01-X-18,L-02-L-04,L-07,L-08, L-12,L-13,L-15,L-18 possessed evidently improved antiproliferative effects(GI₅₀ < 0.1μmol/L) than the mother compound DHA with GI₅₀ value of 0.73μmol/L.In all the compounds,X-11 showed the strongest activity against HL-60 cells growth,GI50 = 0.0159μmol/L.The antiproliferative activities some target compounds in murine leukemia P388 cells and P388/Adr cells were determined compared with DHA and Adriamycin.All of these tested compounds showed preferable activity against these two tumor cells,but the majority of these artemisinin derivatives were more effective against P388 cells than P388/Adr cells. Compounds Y-34,Y-35,L-18 etc had similar activities against these two tumor cells,and compounds Y-13,X-01,L-13,L-23 etc were more effective against P388/Adr cells than P388 cells.The compound L-12 with phenyl on the N-4 position of piperazine evidently circumvented multidrug resistance mechanism（GI50 = 0.0449μmol/L）.From the primary structure-activity relationships of HL-60 cells growth inhibition,we can conclude that:①artemisinin ethers are more potent than artemisinin esters inhibiting cell growth,and artemisinin aromatic ethers are more potent artemisinin aliphatic ethers in some categories;②the type and position of substituted group could affect antiproliferative activities,but the a,P-unsaturated ketone was not an essential group to affect antiproliferative activities in the kind of Y;③the different substituted groups didn’t significantly increased antiproliferative effects,and the structure of CA-4 analog was the important to activities in the kind of X;④the compounds with phenyl on the N-4 position of piperazine showed a significantly increased antiproliferative effects in in the kind of L.The apoptosis-inducing activities of DHA,Y-17 and Y-23 with significant cell growth inhibition activity in were HL-60 cells evaluated using AO/EB double staining assay and fluorescence-activated cell sorting analysis..HL-60 cells were treated with y-17 or y-23 at 0.8μmol/L for 24h,the percentage of apoptosis cells was 80%...