Cytotoxicity-guided fractionation of the methanol soluble part of the dichloromethane extract of the leaves of Warionia saharae led to the isolation of the two new guaianolide-type sesquiterpene lactones, 5 alpha H-3 beta,4 beta-epoxy-14-oxo-guaia-1(10),11(13)-dien-6 alpha,12-olide (1), 5 alpha H-2