Abstract: AIM:To study the chemical constituents and bioactivity of the seeds of Crataegus pinnatifida.METHODS:The chemical constituents were isolated and purified by macroporous adsorptive resin D101,silica gel,and ODS column chromatography,and preparative HPLC.Their structures were elucidated on the basis of spectroscopic methods.In addition,the cytotoxic activities of compounds 1-4 were investigated on OPM2 and RPMI-8226 cells.RESULTS:Four compounds were obtained and their structures were identified as(7S,8S)-4-2-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-1-(hydroxymethyl) ethoxy-3,5-dimethoxybenzaldehyde(1),(+)-balanophonin(2),erythro-guaiacylglycerol--coniferyl aldehyde ether(3),buddlenol A(4).CONCLUSION:Compound 1 is a novel norlignan,while compounds 1-4 exhibited marginal inhibition on the proliferation of OPM2 and RPMI-8226 cells.