Euphorbia kansui is a commonly used traditional Chinese medicine for the treatment of edema,pleural effusion,and asthma,etc.According to the previous researches,terpenoids in E.kansui possess various biological activities,e.g.,anti-virus,anti-allergy,antitumor effects.In this work,twenty five terpenoids were isolated from E.kansui,including thirteen ingenane-and eight jatrophane-type diterpenoids(with two new compounds,kansuinin P and Q)and four triterpenoids.Eighteen of them were analyzed by MTS assay for in vitro anticancer activity in five human cancer cell lines.Structure-activity relationship for 12 ingenane-type diterpenoids in colorectal cancer Colo205 cells were preliminary studied.Significant anti-proliferation activities were observed in human melanoma cells breast cancer MDA-MB-435 cells and Colo205 cells.More than half of the isolated ingenane-type diterpenoids showed inhibitory activities in MDA-MB-435 cells.Eight ingenane-and one jatrophane-type diterpenoids possessed much lower IC_(50) values in MDA-MB-435 cells than positive control staurosporine.Preliminary structure-activity relationship analysis showed that substituent on position 20 was important for the activity of ingenane-type diterpenoids in Colo205 cells and substituent on position 3 contributed more significant biological activity of the compounds than that on position 5 in both MDA-MB-435 and Colo205 cells. Euphorbia kansui is a commonly used traditional Chinese medicine for the treatment of edema, pleural effusion, and asthma, etc.According to the previous researches,terpenoids in E.kansui containing various biological activities,eg,anti-virus,anti-allergy,antitumor effects.In this work,twenty five terpenoids were isolated from E.kansui,including thirteen ingenane-and eight jatrophane-type diterpenoids(with two new compounds,kansuinin P and Q)and four triterpenoids.Eighteen of them were analyzed by MTS assay for In vitro anticancer activity in five human cancer cell lines.Structure-activity relationship for 12 ingenane-type diterpenoids in colorectal cancer Colo205 cells were next studied.Significant anti-proliferation activities were observed in human melanoma cells breast cancer MDA-MB-435 cells and Colo205 cells.More than half of the isolated ingenane-type diterpenoids inhibitory activities in MDA-MB-435 cells.Eight ingenane-and one jatrophane-type diterpenoids possessed muc h lower IC_(50) values ​​in MDA-MB-435 cells than positive control staurosporine.Preliminary structure-activity relationship analysis revealed that substituent-position 20 was important for the activity of ingenane-type diterpenoids in Colo205 cells and substituent on position 3 More significant biological activity of the compounds than that on position 5 in both MDA-MB-435 and Colo205 cells.