New antitumor bicyclic hexapeptides, ra-xi, -xii, -xiii and -xiv from rubia cordifolia

Abstract

Four new bicyclic hexapeptides, named as RA-XI, -XII, XIII and -XIV were isolated from Rubia cordifolia and showed potent antitumor activities against P-388. The structures were elucidated from spectroscopic and chemical evidences. RA-XII, XIII and -XIV were proved to be unique bicyclic hexapeptidic glucosides. © 1992, The Pharmaceutical Society of Japan. All rights reserved.