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

The distribution of forests on Hainan Island in 2008.

<p>The distribution of forests on Hainan Island in 2008.</p

Estimations of carbon density in different layers of major forest ecosystems in 2008 with uncertainty analysis (Mean±SE).

<p>**hard wood (wood density >0.7); soft wood (wood density <0.7).</p><p>Estimations of carbon density in different layers of major forest ecosystems in 2008 with uncertainty analysis (Mean±SE).</p

The C storage in different layers of forest ecosystems on Hainan Island in 2008.

<p>Tree C includes C in above- and below-ground biomass. Values are means ± SE.</p

The conversion formulas used in previous studies for estimating the biomass of dominant tree species on Hainan Island.

<p>*: n is the number of trees used in developing the regression model.</p><p>**: R² is the coefficient of determination. All the regression models are significant (P<0.05).</p>#<p>: hard wood (wood density >0.7); soft wood (wood density <0.7).</p><p>The conversion formulas used in previous studies for estimating the biomass of dominant tree species on Hainan Island.</p

Total C storage of different forest ecosystems on Hainan Island during 1993–2008.

<p>CP: <i>Casuarina</i> plantation; NP (soft wood): Native broad-leaved species plantation (soft wood); EP: <i>Eucalyptus</i> plantation; TRF: Tropical rain forest (natural+secondary); PP: <i>Pinus</i> plantation; CLP: <i>Cunninghamia lanceolata</i> plantation; AP: <i>Acacia</i> plantation; NP (hard wood): Native broad-leaved species plantation (hard wood); MP: Mixed coniferous and broad-leaved tree species plantation; RP: Rubber plantation.</p

Carbon (C) density, forest area, and C storage of forest ecosystems on Hainan Island.

<p>*In 2008, rubber plantations, orchards, and mixed coniferous and broad-leaved tree species plantations were included in the statistics. The rubber plantation and orchard were first accounted, and some <i>Pinus</i> plantation developed into mixed coniferous and broad-leaved tree species plantation.</p><p>**hard wood (wood density >0.7); soft wood (wood density <0.7).</p><p>Carbon (C) density, forest area, and C storage of forest ecosystems on Hainan Island.</p

Total forest coverage and natural forest coverage on Hainan Island from 1940s to 2010s.

<p>Data are from the National Forest Resources Inventory.</p