Three pairs of novel enantiomeric 8-O-4′ type neolignans (1a/1b−3a/3b), together with seven known analogues (4−10), were isolated from the whole plants of Saussurea medusa. Their structures were elucidated by extensive spectroscopic data analysis and electric circular dichroism (ECD) calculations after chiral separations. All compounds were obtained from S. medusa for the first time, and compounds 1−3 and 5−10 had never been obtained from the genus Saussurea previously. The anti-inflammatory activities of the compounds were evaluated by determining their inhibitory activities on the production of NO and inducible nitric oxide synthase (iNOS) expression in LPS-stimulated RAW 264.7 cells. Compounds (+)-1a, (−)-1b and 5−7 inhibited NO production and had IC50 values ranging from 14.3 ± 1.6 to 41.4 ± 3.1 μM. Compound 7 induced a dose-dependent reduction in the expression of iNOS in LPS-treated RAW 264.7 cells. Molecular docking experiments showed that all active compounds exhibited excellent docking scores (<−7.0 kcal/mol) with iNOS. Therefore, compounds (+)-1a, (−)-1b and 5−7 isolated from the whole plants of S. medusa may have therapeutic potential in inflammatory diseases.
Keywords: ECD calculation; Saussurea medusa; anti-inflammatory activity; iNOS protein; molecular docking; neolignans.