Five new diarylbutyrolactones and sesquilignans (1A/1B: - 4: ), including one pair of enantiomers (1A/1B: ), together with 10 known analogues (5: - 14: ), were isolated from the whole plants of Saussurea medusa. Compound 1: was found to possess an unusual 7,8'-diarylbutyrolactone lignan structure. Separation by chiral HPLC analysis led to the isolation of one pair of enantiomers, (+)-1A: and (-)-1B: . The structures of the new compounds were elucidated by extensive spectroscopic data. All compounds, except compounds 5, 7: and 9: , were isolated from S. medusa for the first time. Moreover, compounds 1: - 4, 8: and 10: - 14: had never been obtained from the genus Saussurea previously. Compounds (+)- 1A, 2, 5, 7: , and 9: - 11: were found to inhibit the lipopolysaccharide (LPS)-induced release of NO by RAW264.7 cells with IC50 values ranging from 10.1 ± 1.8 to 41.7 ± 2.1 µM. Molecular docking and iNOS expression experiments were performed to examine the interactions between the active compounds and the iNOS enzyme.
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