Isolation and structure of cyclosenegalins A and B, novel cyclopeptides from the seeds of Annona senegalensis

Two new cyclopeptides, cyclosenegalin A, cyclo(Pro1-Gly2-Leu3-Ser4-Ala5-Val6-Thr7-) (1) and cyclosenegalin B, cyclo(Pro1-Gly2-Tyr3-Val4-Tyr5-Pro6-Pro7-Val8-) (2), have been isolated from the methanol extract of the seeds of Annona senegalensis Pers., along with the known cyclic peptide, glabrin A. The structures were elucidated on the basis of the MS/MS fragmentation, using a Q-TOF mass spectrometer equipped with an ESI source, chemical degradation and extensive 2D-NMR.