Two new chlorinated sesquiterpenes from Sigesbeckia orientalis.

Two new chlorinated guaianane-type sesquiterpenes (named chlosigesolides A and B) together with eight known compounds were isolated from the leaves and twigs of Sigesbeckia orientalis. Their structures were determined by analysis of HR-ESI-MS, 1D- and 2D-NMR spectral data as well as comparison with the literature. Absolute configurations of new compounds were elucidated by NOESY and ECD methods. Chlosigesolide A inhibited NO production in LPS-stimulated RAW264.7 macrophages with IC₅₀ value of 10.9 ± 0.8 μM. Other compounds exhibited inhibitory activity at IC₅₀ in range of 26.5 to 49.7 μM. [ABSTRACT FROM AUTHOR]