Cycloleonuripeptides A, B and C, three new proline-rich cyclic nonapeptides from Leonurus heterophyllus

Three new proline-rich cyclic nonapeptides, cycloleonuripeptides A: cyclo (-Gly-Pro-Pro-Pro-Tyr-Pro-Pro-Met-Ile-), B: cyclo (-Gly-Pro-Pro-Pro-Tyr-Pro-Pro-Met(O)-Ile-), and C: cyclo (-Gly-Pro-Pro-Pro-Tyr-Pro-Pro-Met(O)-Ile-), have been isolated from the fruits of Leonurus heterophyllus and their structures were elucidated by extensive 2D NMR methods, chemical degradation and transformation. Cycloleonuripeptides B and C, both of which are epimer, showed cell growth inhibitory activity.