Clausenlanins A and B, Two Leucine-Rich Cyclic Nonapeptides from Clausena lansium

Abstract Two new cyclic nonapeptides, named clausenlanins A (1) and B (2), were isolated from the roots and rhizomes of Clausena lansium. Their structures were elucidated as cyclo-(Gly1-l-Leu2-l-Ile3-l-Leu4-l-Leu5-l-Leu6-l-Leu7-l-Leu8-l-Leu9) (1) and cyclo-(Gly1-l-Leu2-l-Val3-l-Leu4-l-Leu5-l-Leu6-l-Leu7-l-Leu8-l-Leu9) (2) respectively on the basis of extensive spectroscopic analysis, particularly 2D NMR spectra taken at the temperature of 338 or 303 K and MS. Graphical Abstrac