Isolation and antitumor activity of cyclic hexapeptides isolated from Rubiae radix

The details of the isolation and antitumor activity of cyclic hexapeptides (RA-VII, RA-V, RA-IV and RA-III) isolated from Rubia cordifolia are reported. Studies on a spectrum of experimental tumors in mice revealed that the peptides exhibited significant activity against leukemias and ascites tumors, P-388, L1210, B-16 melanoma and solid tumors, colon 38, Lewis lung carcinoma and Ehrlich carcinoma. RA-V had an especially potent effect on MM2 mammary carcinoma in mice. The effective dose range of RA-IV against P-388 leukemia was different from those of the other cyclic hexapeptides.