New cyclic peptides from the seeds of Annona squamosa L. and their anti-inflammatory activities.

Two new cyclic peptides, cyclosquamosin H ( 1) and I ( 2), together with six known cyclic peptides, squamin A ( 3), squamin B ( 4), cyclosquamosin A ( 6), cyclosquamosin D ( 7), cyclosquamosin E ( 8), and cherimolacyclopeptide B ( 9), were isolated from the seeds of Annona squamosa. All structures were confirmed by 2D nuclear magnetic resonance, chemical evidence, and electrospray ionization-mass spectromotry/mass spectrometry (ESI-MS/MS). Compound 9 was isolated from this plant for the first time. In the anti-inflammatory assay, compound 7 showed an inhibitory effect on the production of pro-inflammatory cytokines within lipopolysaccharide and Pam3Cys-stimulated J774A.1 macrophages.