Cyclopurpuracin, a cyclopeptide from Annona purpurea seeds

From a 60% hydroalcoholic extract of the seeds of Annona purpurea, a novel cyclooctapeptide, cyclopurpuracin (1), or cyclo(-Pro(1)-Gly(2)-Phe(3)-ILe(4)-Gly(5)-Ser(6)-Pro(7)-Va(l)8-), has been isolated. The structure of cyclopurpuracin (1) was determined by de novo sequencing based on MS/ MS spectra and 1D and 2D NMR techniques (H-1, C-13, HSQC, HMBC, COSY and ROESY).