Suberitine A–D, Four New Cytotoxic Dimeric Aaptamine Alkaloids from the Marine Sponge <i>Aaptos suberitoides</i>

Suberitine A–D (<b>1</b>–<b>4</b>), four new bis-aaptamine alkaloids with two aaptamine skeleton units, 8,9,9-trimethoxy-9<i>H</i>-benzo[<i>de</i>][1,6]-naphthyridine and demethyl(oxy)-aaptamine, linked through a rare C-3–C-3′ or C-3–C-6′ <b>σ</b>-bond between the 1,6-naphthyridine rings, together with two known monomers <b>5</b> and <b>6</b>, were isolated from the marine sponge <i>Aaptos suberitoides</i>. Their structures were elucidated using NMR spectroscopy. Compounds <b>2</b> and <b>4</b> showed potent cytotoxicity against P388 cell lines, with IC₅₀ values of 1.8 and 3.5 μM, respectively

(+)- and (−)-Spiroreticulatine, A Pair of Unusual Spiro Bisheterocyclic Quinoline-imidazole Alkaloids from the South China Sea Sponge <i>Fascaplysinopsis reticulata</i>

A pair of novel bisheterocyclic quinoline-imidazole alkaloids, (+)- and (−)-spiroreticulatine (<b>1</b>), were isolated from the South China Sea sponge <i>Fascaplysinopsis reticulata</i>. The structures and absolute configurations were elucidated by comprehensive spectroscopic analysis, single-crystal X-ray diffraction, and quantum chemical calculation methods. Spiroreticulatine is the first example of a sponge-derived natural spiro quinoline-imidazole alkaloid that may derive from tryptophan and 1,3-dimethylurea. Compound <b>1</b> showed inhibitory activity on IL-2 production but inactive against normal tumor cell lines

Cytotoxic Polyketide Derivatives from the South China Sea Sponge <i>Plakortis simplex</i>

Five new polyketides, plakortoxides A (<b>1</b>) and B (<b>2</b>), simplextones C (<b>3</b>) and D (<b>4</b>), and plakorsin D (<b>5</b>), together with six known analogues (<b>6</b>–<b>11</b>) were isolated from the South China Sea sponge <i>Plakortis simplex</i>. Their structures were identified by spectroscopic and chemical methods, including NMR, MS, and IR. Experimental and calculated ECD spectra and the modified Mosher’s method were used to determine the absolute configurations. Structurally, both plakortoxides A and B feature a butenolide coupled to an epoxide moiety, while simplextones C and D consist of γ-butyrolactone and cyclopentane moieties, and plakorsin D is a furan acetic acid polyketide. The cytotoxic activities of the isolates were tested, and compounds <b>8</b>, <b>10</b>, and <b>11</b> showed potent cytotoxicity against both K562 and HeLa tumor cell lines with IC₅₀ values ranging from 0.8 to 5.3 μM. Compound <b>3</b> showed significant inhibitory activity against c-Met kinase

Samholides, Swinholide-Related Metabolites from a Marine Cyanobacterium cf. <i>Phormidium</i> sp.

Cancer cell cytotoxicity was used to guide the isolation of nine new swinholide-related compounds, named samholides A–I (<b>1</b>–<b>9</b>), from an American Samoan marine cyanobacterium cf. <i>Phormidium</i> sp. Their structures were determined by extensive analysis of 1D and 2D NMR spectroscopic data. The new compounds share an unusual 20-demethyl 44-membered lactone ring composed of two monomers, and they demonstrate structural diversity arising from geometric isomerization of double bonds, sugar units with unique glyceryl moieties and varied methylation patterns. All of the new samholides were potently active against the H-460 human lung cancer cell line with IC₅₀ values ranging from 170 to 910 nM. The isolation of these new swinholide-related compounds from a marine cyanobacterium reinvigorates questions concerning the evolution and biosynthetic origin of these natural products