dicarabrol a new dimeric sesquiterpene from carpesium abrotanoides l a new dimeric sesquiterpene dicarabrol 1 together with three known sesquiterpenes carabrol 2 1113dehydroivaxillin 3 and 2desoxy4epipulchellin 4 were isolated from the whole plant of carpesium abrotanoides l their structures were elucidated on the basis of spectroscopic analysis and single crystal xray diffraction analysis compound 1 possessed a dimeric sesquiterpene core featured with a cyclopentane ring connecting two sesquiterpene lactone units rarely discovered in nature dicarabrol 1 as well as three known sesquiterpenes 24 had potent in vitro cytotoxicities against the k562 mcf7 hela du145 u937 h1975 sgc7901 a549 molt4 and hl60 cell lines with ic50 values ranging from 010 to 467 m while they showed significant antiviral h1n1 and h3n2 activities furthermore compounds 1 3 and 4 displayed significant antimycobacterial activity ic50 37 60 and 76 m respectively