Two new cyclooctapeptides, cherimolacyclopeptide A, cyclo(Pro¹ -Gln² -Thr³ -Gly⁴ -Met⁵ -Leu⁶ -Pro⁷ -Ile⁸ -) (1) and the related cherimolacyclopeptide B, cyclo(Pro¹ -Gln² -Thr³ -Gly⁴ -Mso⁵ -Leu⁶ -Pro⁷ -Ile⁸ -) (2), have been isolated from the methanol extract of the seeds of Annona cherimola Miller. The sequences 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-heteronuclear NMR. The three-dimensional solution structure of cherimolacyclopeptide A (1) determined by ¹H NMR data and molecular modelling is characterised by the presence of two β turns and a new type of β-bulge.