Lamellarin Sulfates from the Pacific Tunicate Didemnum ternerratum

Six new lamellarin sulfates (1–6) were isolated from the methanolic extract of the Pacific tunicate Didemnum ternerratum, collected from the Kingdom of Tonga. Mass spectrometric molecular networking through the GNPS platform was used to target the isolation of 1–6. Planar structures were elucidated through a combination of NMR and MS experiments. Through comparison of experimental and calculated ECD spectra, the absolute configurations of atropisomers 2–5 were determined, with their energetic barriers to racemization also determined computationally. The cytotoxicity of the compounds was tested against the human colon carcinoma cell line HCT-116, where lamellarin D-8-sulfate (5) exhibited moderate activity with an IC50 of 9.7 μM.