Tetrasargltones A and B, Fully Helically Polymerized Lindenane Sesquiterpenoid Tetramers from <i>Sarcandra glabra</i>

Tetrasargltones A and B (<b>1</b> and <b>2</b>, respectively), representing the first examples of lindenane sesquiterpenoid (LS) tetramers, were isolated from <i>Sarcandra glabra</i>. Their structures were fully elucidated via HR-MS and NMR, with their authenticity further confirmed by X-ray diffraction. Structurally, <b>1</b> and <b>2</b> possess two unprecedented fully helically polymerized carbon skeletons, which are formed through plausible sequential Diels-Alder cycloadditions at different sites of the triene LS precursor. Biologically, <b>1</b> and <b>2</b> exhibit cytotoxic activity against five cancer cell lines, with <b>2</b> showing the best activity in HCT116 cells (IC₅₀ = 2.51 ± 0.13 μM) and exerting its cytotoxic effects through NF-κB pathway inhibition.