Germacranolides from Mikania guaco

Fourteen novel sesquiterpene lactones of the germacranolide type have been isolated from the aerial parts of Mikania guaco: six costunolide, two melam polide and six germacra-4-trans, 10(14),11(13)-trien-12,6 alpha -olide deri vatives, Except for one compound all the others possess a carbonyl function at C-9. Eight were obtained in the form of four isomer pairs which were di fficult to separate. Structure elucidation was based on mass and 1D and 2D NMR measurements. Low energy conformations were obtained by quantum mechani cal calculations. Pyrrolizidine alkaloids could not be detected. (C) 2001 E lsevier Science Ltd. All rights reserved.