Lindenane-Based Sesquiterpenoid Hetero-Oligomers with Diverse Skeletons and Extracellular Regulated Protein Kinases Inhibitory Activity from Sarcandra glabra

Sarcglabtenes A–G (1–7), seven lindenane-based sesquiterpenoid hetero-oligomers with six unprecedented skeletons, along with five new biosynthetic analogues sarcglabtenes H–L (8–12), were isolated from Sarcandra glabra. Their structures including absolute configurations were comprehensively elucidated using HR-MS, NMR, ECD, and single crystal X-ray diffraction. Structurally, sarcglabtenes A–G are lindenane hetero-oligomers including a geranyl homogentisic acid (1/2), geranylgeranyl p-toluquinone (3/4), germarane (5), campholenal (6/7) derivatives, for which plausible biosynthesis pathways are also proposed. In bioassays, 1–4 exhibited cytotoxic activity against five cancer cell lines, and in particular, 4 acted as extracellular-regulated protein kinase (Erk) inhibitor of the MAPK signaling pathway involved in apoptosis.