Croargoids A-G, Eudesmane Sesquiterpenes from the Bark of Croton argyratus

Seven new sesquiterpenes, named croargoid A-G (1-7), were isolated from the bark of Croton argyratus. Compounds 1-4 were the first examples of eudesmane sesquiterpene lactones containing C-5-OH group. Compound 7 was a highly degraded eudesmane sesquiterpene possessing a rare eleven-carbon skeleton. Their structures with stereochemistry were mainly elucidated by NMR analyses in combination with MS and ECD data. Cytotoxicities and NO inhibitions of all isolates were evaluated and only compound 5 showed moderate NO inhibitory activity.