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Natural product dimers have intriguing structural features and often have remarkable pharmacological activities. We report here two uncommon marine gorgonian-derived symmetric dimers, weizhouochrones A (

Two novel rearranged Diels-Alder adducts, morunigrines A (1) and B (2), and four new prenylated flavonoids, morunigrols A-D (3-6), were isolated from the twigs of Morus nigra, together with four known prenylated phenolic compounds, including two flavonoids (7 and 8) and two 2-arylbenzofurans (9 and 10). Morunigrines A (1) and B (2) are a novel class of Diels-Alder adducts with unprecedented carbon skeletons featuring a rearranged chalcone-stilbene/2-arylbenzofuran core decorated with a unique methylbiphenyl moiety. The structures of the new compounds were assigned by analysis of spectroscopic data. The absolute configuration of compound 6 was determined by the measurement of specific rotation. A plausible biogenetic pathway for 1 and 2 is also proposed. Compounds 1 and 2 exhibited more potent protein tyrosine phosphatase 1B inhibitory activity with IC50 values of 1.8 ± 0.2 and 1.3 ± 0.3 μM, respectively, than that of the positive control oleanolic acid (IC50, 2.5 ± 0.1 μM).

Nine new isomalabaricane terpenoids (

Two novel rearranged Diels-Alder adducts, morunigrines A (

A new diacylguanidine, actinofide (1), has been isolated from the marine mollusk Actinocyclus papillatus. The structure, exhibiting a guanidine moiety acylated by two terpenoid acid units, has been established by spectroscopic methods and secured by synthesis. Following this, a series of structural analogues have been synthesized using the same procedure. All of the compounds have been evaluated in vitro for the growth inhibitory activity against a variety of cancer cell lines.

Two new prenylgermacrane-type diterpenoids, lobophytumins A and B (1 and 2), two new prenyleudesmane-type diterpenoids, lobophytumins C and D (3 and 4), and two new spatane-type diterpenoids, lobophytumins E and F (5 and 6), were isolated from the Hainan soft coral Lobophytum crista turn Tixier-Durivault. Their structures, including relative configuration, were elucidated by detailed analysis of spectroscopic data and by comparison with related known compounds. In addition, the absolute configuration of lobophytumin C (3) was tentatively assigned by comparing its specific rotation with that of the closely related model compound (-)-beta-selinene (8). On the basis of biogenetic considerations, the absolute configurations of lobophytumins A, B, and D F were also tentatively suggested. This is the first report of spatane-type diterpenoids from a soft coral source. The present work supports Faulkner's proposal of prenylgermacrene as the precursor of many diterpenes. In a bioassay, lobophytumins C and D (3 and 4) showed weak in vitro cytotoxicities against the tumor cell lines A-549 and HCT-116.

Eight new marine steroids, characterized by either the presence of an aromatic ring or a cross-conjugated dienone system in ring A, were isolated from the Hainan soft coral Dendronephthya studeri Ridley. Their structures were elucidated on the basis of detailed spectroscopic analysis and by comparison of their NMR data with those reported in the literature.

Five new sesquiterpenes, named lingshuiolides A (1) and B (2), lingshuiperoxide (6), isodysetherin (10), and spirolingshuiolide (12), along with several known related analogues (7- 9, 11, and 13- 15), were isolated from the Hainan marine sponge Dysidea septosa. The structures of new compounds 1, 2, 6, 10, and 12 were determined by detailed analysis of 1D and 2D NMR spectra and by comparison with related model compounds. The absolute configuration of lingshuiolide B (2) was established by using the modified Mosher's method. Spirolingshuiolide (12) represents the first example of a sesquiterpene with a rearranged drimane skeleton. Compounds 7- 9 and 15 exhibited significant inhibitory activity against human protein tyrosine phosphatase 1B (hPTP1B), an enzyme involved in the regulation of insulin signaling. In particular, 15 showed the most potent effect, with an IC 50 value of 1.9 microg/mL.

One new laurane sesquiterpenoid, 3beta-hydroxyaplysin (2), and two novel rearranged sesquiterpenes, laurokamurenes A (3) and B (4), together with three known related compounds, 3alpha-hydroxydebromoaplysin (1), debromoaplysin (6), and laurinterol (7), have been isolated from the Chinese red alga Laurencia okamurai. Their structures, including relative stereochemistry, were determined on the basis of detailed interpretation of 2D NMR spectra and comparison with related known compounds.

Petroformynes are unusual metabolites contained in the Mediterranean sponge Petrosia ficiformis. The structure and absolute stereochemistry of the most abundant of these compounds, which display long unbranched alkyl chains, have only recently been rigorously proven. The structures of twelve minor compounds are now reported, providing a better understanding of the chemistry of P. ficiformis. In addition, complete spectroscopic characterization of eleven partial structures (a-k) frequently contained in P. ficiformis metabolites is provided as an aid to future structure elucidation among compounds of this type.

Three new polyoxygenated steroids, nanjiol A (1), B (2), and C (3), were isolated from an East China Sea soft coral Nephthea bayeri, and their structures were characterized by spectroscopic methods and comparison with known compounds. The new molecules were structurally related to (20S)-cholesta-1,4-diene-18,20-diol-3-one (4), a typical metabolite from the black coral Antipathes subpinnata.

Four diterpenes, tritoniopsins A-D (1-4), have been isolated from the South China Sea nudibranch Tritoniopsis elegans and its prey, the soft coral Cladiella krempfi. They display an unprecedented pyran ring in the cladiellane framework, thus representing a novel cladiellane-based diterpene family. Their structures have been mainly characterized by NMR and mass spectrometric techniques, whereas the relative configuration of compound 1 was secured by X-ray analysis. Antiproliferative assays on tumor and nontumor cell lines have been carried out for the main metabolite, tritoniopsin B (2).

A series of nine casbane diterpenes, compounds 5-13, exhibiting either cis or trans ring junctions were isolated from the Hainan soft coral Sinularia depressa. The structures of this group of compounds, the basic member of which was named depressin (5), were established by detailed spectroscopic analysis. In addition, the absolute configuration of the main metabolite, 10-hydroxydepressin (7), and of its epimer, 1-epi-10-hydroxydepressin (8), was determined by a combination of conformational analysis and the modified Mosher's method. A stereochemical relationship between all isolated molecules was investigated by analyzing their circular dichroism profiles. Antiproliferative and antibacterial activities of the depressins were also evaluated.

A series of isocyanides, compounds 4-11, including diterpenes never before found in Phyllidiid nudibranchs, have been isolated from a Chinese population of the nudibranch Phyllidiella pustulosa. Three new sesquiterpenes (8, 10, and 11), with eudesmane, guaiane, and bisabolane skeletons, respectively, have been characterized by spectral methods and chemical comparison with known related molecules. The absolute stereochemistry of the major metabolite, the isocyanide 8, an enantiomer of the known sponge metabolite stylotelline (12), has also been determined.