New Antimitotic Bicyclic Peptides, Celogentins D—H, and J, from the Seeds of Celosia argentea.

Abstract

Abstract Six new bicyclic peptides, celogentins D–H ( 1–5 ) and J ( 6 ) have been isolated from the seeds of Celosia argentea, and the structures including its absolute stereochemistry were determined by using extensive NMR methods and chemical means. Celogentins E–H ( 2–5 ) and J ( 6 ) showed potent inhibition of tubulin polymerization, while the inhibitory activity of celogentin D ( 1 ) was modest. Structure–activity relationship study indicates that ring size of the bicyclic ring system including unusual βs-Leu, Trp, and His residues would be important for their biological activity.