New antitumor cyclic hexapeptides RA-IV, RA-III, RA-II and RA-I were isolated as minor constituents of Rubia cordifolia. Their structures were elucidated by means of various instrumental and chemical analyses. From a comparison of the antitumor activities of 7 products derived by oxidizing RA-V with 2, 3-dichloro-5, 6-dicyano-p-benzoquinone and 6 native cyclic hexapeptides isolated from R. cordifolia, it is surmised that the active site in the RA-series is present at the α-side of RA molecules.
作为茜草的次要成分,分离出了新的抗肿瘤环六肽 RA-IV、RA-III、RA-II 和 RA-I。通过各种仪器和化学分析,阐明了它们的结构。通过比较 RA-V 与 2,3-二氯-5,6-二氰基对苯醌氧化生成的 7 种产物和从茜草中分离出的 6 种原生环六肽的抗肿瘤活性,推测 RA 系列的活性位点位于 RA 分子的 α 侧。