Cycloleonuripeptides E and F, cyclic nonapeptides from Leonurus heterophyllus.

Two new cyclic nonapeptides, cycloleonuripeptide E, cyclo (-Ala-Pro-Ile-Val-Ala-Ala-Phe-Thr-Pro-), and cycloleonuripeptide F, cyclo (-Gly-Tyr-Pro-Leu-Pro-Phe-Tyr-Pro-Pro-), have been isolated from the fruits of Leonurus heterophyllus, and their structures were elucidated by 2D NMR analysis and chemical degradation. Cycloleonuripeptides E (1) and F (2) showed moderate vasorelaxant effects on rat aorta.