Chloraserrtone A, a Sesquiterpenoid Dimer from Chloranthus serratus

Chloraserrtone A (1), a new sesquiterpenoid dimer with two lindenane-type sesquiterpenoid monomers bridged by two six-membered rings, was obtained from Chloranthus serratus. A combination of UV, IR, NMR, HRESIMS, and X-ray diffraction data were used to elucidate the structure of 1. Compound 1 represents the first lindenane-type sesquiterpenoid dimer with extremely unique C-15–C-15′, C-4–C-6′, and C-6–C-11′ linkages to form two six-membered rings between the monomeric units. A plausible biosynthesis toward chloraserrtone A is proposed. This new compound (1), together with the known lindenane dimers (2–11), were assessed for their inhibitory effects on lipopolysaccharide-induced NO production in RAW264.7 cells. Compound 6 showed activity with an IC₅₀ value of 3.7 μM.