Two cyclopeptides from the seeds of Annona cherimola

The structures of cherimolacyclopeptides E and F were elucidated on the basis of their MS/MS spectra, chemical degradation and extensive 2D NMR experiments. Bioassay-guided fractionation of cytotoxic of methanol extract of the seeds of Annona cherimola provided two novel cyclic peptides, cherimolacyclopeptide E ( 1) and cherimolacyclopeptide F ( 2), which exhibited significant cytotoxic activity against the KB (human nasopharyngeal carcinoma) cell culture system. The peptide 1 and 2 were elucidated by MS/MS fragmentation experiments using a Q-TOF mass spectrometer equipped with an ESI source, extensive 2D NMR analyses and chemical degradation.