Mallotumides A–C: Potent Cytotoxic Cycloheptapeptides from the Roots of Mallotus spodocarpus

The structures of potent cytotoxic cycloheptapeptides, mallotumides A-C (1-3, respectively) isolated from the roots of Mallotus spodocarpus Airy Shaw, were elucidated by extensive spectroscopic analysis. The absolute configuration of 1 was determined by single-crystal X-ray crystallographic data. All three cycloheptapeptides exhibited potent cytotoxicity against various cancer cell lines with IC50 values ranging from 0.60 to 4.02 nM.