Three　new　lignans,　Pronaphthalide　A　(1),　Procumbiene　(2),　and　Procumbenoside　(3),　along　with　a　novel　natural　product　Juspurpudin　(4),　and　twelve　other　known　lignans　were　isolated　from　justicia　procumbens.　The　structures　of　the　new　compounds　were　elucidated　by　extensive　spectroscopic　analyses　and　the　data　of　3　provided　insight　into　the　conformational　equilibria　existing　in　it.　All　compounds　were　evaluated　for　their　in　vitro　cytotoxic　activity　against　Human　LoVo　and　BGC-823　cell　lines　except　for　compound　2,　and　eight　of　them　were　found　to　possess　potent　cytotoxicity.　The　structure-activity　relationship　(SAR)　analysis　revealed　that　(i)　the　parent　structure　of　2-carbonyl　arylnaphthalide　lactone　attached　with　6　and　7-OMe　was　the　essential　element;　(ii)　the　polarity　of　substituents　on　C-4　might　significantly　affect　the　activity;　(iii)　a　proper　cyclic　lipophilic　group　at　the　C-3　＇＇　and　C-5　＇＇　of　apiofuranose　on　C-4　might　enhance　the　activity,　which　could　optimize　the　application　of　3　similar　to　VP-16.　(C)　2014　Elsevier　B.V.　All　rights　reserved.