A new cyclic peptide from the fibrous root of Pseudostellaria heterophylla.

A new cyclic peptide, Pseudostellarin K (1), together with thirteen known compounds, including two cyclic peptides (2 and 3), one ß-carboline alkaloid (4), two amides (5 and 6), three phenylpropanoids (7-9) and other compounds (10-14), were isolated from the fibrous root of Pseudostellaria heterophylla. Their structures were elucidated by extensive spectroscopic analysis. Compounds 1, 4-6, 10 were isolated from the genus pseudostellaria for the first time. All compounds were evaluated for cytotoxic activities against MCF-7, A549, HCT-116 and SGC-7901 cell lines by MTT assay. Unfortunately, all these compounds displayed weak cytotoxic activities.