Eight new cytotoxic annonaceous acetogenins from the seeds of Annona squamosa

Eight new annonaceous acetogenins, squamotin A-D ( 1-4 ), annosquatin IV-V ( 5 and 6 ), muricin O ( 7 ) and squamosten B ( 8 ), together with four known ones ( 9-12 ) were isolated from the seeds of Annona squamosa . Their structures were elucidated by chemical methods and spectral data. The inhibitory activities of compound 1-9 against three multidrug resistance cell lines were evaluated. All tested compounds showed strong cytotoxicity.