Study On The Anti-proliferative Activity Of Four Schizoterpenoids From Oleaceae

Cancer incidence and mortality are rising rapidly worldwide.While great strides have been made in the treatment of cancer in recent decades,we still face many open challenges to existing cancer therapies,such as adaptive resistance.Natural products,as the main drug source library,play a vital role in the development of anti-tumor drugs.Secoiridoids,isolated from Oleaceae family,which are now widely used in the fields of food and medicine,have been extensively investigated in recent years and have been shown to possess a variety of pharmacological effects.Antitumor activity is one of their main biological activities.The aim of this work was to study the in vitro anti-cancer activities of four 10-oxyderivatives of oleoside secoiridoids including 10hydroxyoleoside 11-methyl ester(1),10-hydroxyoleoside dimethyl ester(2),10hydroxyligustroside(3)and multifloroside(4)isolated from species in the Oleaceae.1.Antitumor cell proliferation and structure-activity relationshipA431 and A549 cells were selected as the research object,and the effects of the above four compounds on the proliferation of these two tumor cells were detected by MTT method.Our results indicate that these four compounds differ in potency in their ability to inhibit the proliferation of human cancer cell linse A431 and A549,and multifloroside(4)displayed the highest inhibitory activity against A431 cells.Structureactivity relationships suggest that the o-hydroxy-p-hydroxy-phenylethyl group may contribute to the anti-proliferative activity against A431 cells.2.Multifloroside anti-proliferative mechanism of human epidermal squamous cell carcinoma A431 cellsFirst,a colony formation assay was performed to detect the inhibitory effect of multifloroside on the proliferative ability of A431 cells.The plating efficiencies were 84%,46%and 24%for the control,and the 25 μM and 50 μM multifloroside treatments,respectively,and were 0 for the other groups.And the size of the colonies in the multifloroside(50 and 25 μM)treated groups was smaller than that in the control group.These results all illustrate that multifloroside can significantly inhibit the growth of A431 cells.Second,the effect of multifloroside on apoptosis and cell cycle in A432 cancer cells was assessed by flow cytometry.The apoptotic assay suggested multifloroside at high concentration(200 μM)induced cell apoptosis.Cell-cycle analyses indicated the cellcycle distribution was significantly changed,the number of A431 cells in S phase were significantly increased(p<0.001),from 28.55%to 31.78%,49.29%and 55.30%.Third,the effect of multifloroside on ROS and MMP in A432 cancer cells was assessed by flow cytometry.ROS levels were significantly increased in a dose-dependent manner,from 59.34%,74.44%,to 85.59%.Similarly,the MMP was increased when cells were treated with multifloroside at the tested concentrations compared with the control group.Further,Western Blot was used to detect the effects of multiflorosid on cyclin A2,cyclinD1 and p21 of A431 cells.The results showed that the expression levels of cyclin A2 and p21 in A431 treated with multifloroside(25,50,100,and 250 μM)groups increased,but the expression of cyclin D1 decreased.3.These results all suggest that multifloroside may exert its anti-tumor effect through cell-cycle arrest and an increase in the ROS in A431 cells,and further investigations are ongoing in our laboratory.