A xanthanolide diol and a dimeric xanthanolide from Xanthium species.

Extracts of the aerial parts of Xanthium strumarium and fruit of X. pungens afforded a new Xanthanolide diol derivative, 11alpha,13-dihydroxyxanthatin and a new dimeric xanthanolide sesquiterpene lactone, pungiolide C, in addition to some known compounds. The structures of the new compounds were determined by spectroscopic methods particularly high resolution (1)H-, (13)C-NMR and 2D (1)H- (1)H and (1)H- (13)C COSY NMR analysis.