•Eleven highly halogenated chamigrane sesquiterpenoids were isolated from Laurencia composita.•Compositacins B and D are the first examples of chamigranes bearing novel ether bridges.•Compositacins B and C represent the first chamigranes containing a C-10 carbonyl group.•Some isolates exhibited moderate antifungal activity against eight fungi.•Four of eighteen compounds showed marginal cytotoxicity against two human cancer cell lines.Eleven highly halogenated chamigrane sesquiterpenoids, compositacins A–K, including one unusual rearranged chamigrane sesquiterpenoid, compositacin A, were isolated from the red alga Laurencia composita Yamada, along with seven known structural analogues. Compositacins B and D are the first examples of chamigranes bearing an ether bridge involving C-5/C-9 and C-3/C-5, respectively, while compositacins B and C represent the first chamigranes with a C-10 carbonyl group. Their structures were elucidated on the basis of extensive spectroscopic analysis. The absolute configuration of compositacin B was determined by ECD calculation, whereas the absolute configurations of compositacins A and C–L were proposed on biosynthetic grounds by comparison to compositacin B and the related known sesquiterpenoids johnstonol and yicterpene A. We also suggest that the structure of the previously reported sesquiterpenoid laurokamin A should be revised. Cytotoxicity and antifungal activity of these isolates were also investigated. The results showed that compositacin G exhibited good antifungal activity against Microsporum gypseum (Cmccfmza) with a MIC80 value of 4 μg/mL relative to positive controls. Four of the chamigrane halosesquiterpenoids showed marginal cytotoxicity against the A-549 human lung adenocarcinoma cell line with IC50 values ranging from 48.6 to 85.2 μM.Download high-res image (335KB)Download full-size image

•A seco-laurane sesquiterpene and related laurane derivatives were isolated from Laurencia okamurai.•One compound possesses an unprecedented carbon skeleton named seco-laurokamurane.•Another compound represents the fourth example of a laurokamurane-type sesquiterpene in nature.•Some isolates exhibited moderate antifungal activity against four clinical fungi.•Two of eleven compounds showed moderate cytotoxicity against two human cancer cell lines.A ring-cleaved sesquiterpene, named seco-laurokamurone, four laurane-type sesquiterpenes, laurepoxyene, 3β-hydroperoxyaplysin, 3α-hydroperoxy-3-epiaplysin, and 8,10-dibromoisoaplysin, one laurokamurane-type sesquiterpene, laurokamurene D, and one bisabolane-type sesquiterpene, (5S)-5-acetoxy-β-bisabolene, have been isolated from a re-collection of the red alga Laurencia okamurai Yamada, together with six other known sesquiterpenes. Their structures, including relative configuration, were elucidated by detailed analysis of spectroscopic data, and by comparison with data for related known compounds. In addition, on the basis of chemical conversions, degradation results, and biogenetic considerations, the absolute configurations of several of these compounds were also tentatively proposed. seco-Laurokamurone possesses an unprecedented carbon skeleton, formed from an oxidative cleavage of the laurokamurane skeleton, and laurokamurene D represents the fourth example of a laurokamurane-type sesquiterpene from a natural source. The in vitro antifungal activity of many of these compounds was evaluated against four fungi (Cryptococcus neoformans, Candida glabrata, Trichophyton rubrum, and Aspergillus fumigatus), as well as assessing cytotoxicity against HL-60 and A-549 human cancer cell lines. The compounds studied displayed moderate activities, relative to controls.A ring-cleaved sesquiterpene named seco-laurokamurane (1) and six related derivatives (2–7) were isolated from red alga Laurencia okamurai Yamada, together with six known sesquiterpenes. Their structures were elucidated by detailed analysis of spectroscopic data. Compound 1 possesses an unprecedented carbon skeleton named seco-laurokamurane. Selected compounds had moderate antifungal activity and cytotoxicity.

Two new prenylated para-xylenes, named caulerprenylols A (1) and B (2), were isolated from the green alga Caulerpa racemosa, collected from the Zhanjiang coastline, China. The structures of the two metabolites were elucidated on the basis of detailed spectroscopic analysis. This is the first report of prenylated para-xylenes from marine algae and from marine organisms as well. Moreover, caulerprenylol B (2) is also characterized by an uncommon indane ring system. In in vitro bioassays, the new compounds exhibited a broad spectrum of antifungal activity against Candida glabrata (537), Trichophyton rubrum (Cmccftla), and Cryptococcus neoformans (32609) with MIC80 values between 4 and 64 μg/mL when compared to amphotericin B (MIC80 values of 2.0, 1.0, and 4.0 μg/mL, respectively) as a positive control and showed no growth inhibition activity against the tumor cells HL60 and A549.

•Six isomalabaricane triterpenes were isolated from the Hainan sponge Stelletta sp.•A new isomalabaricane triterpene, stellettin N (1), has been characterized.•Stellettin G (4) had a strong PTP1B inhibitory activity with IC50 value of 4.1 ± 0.9 μM.•Stellettin G (4) also exhibited weak cytotoxicity against A549 and HL-60 cells.•The occurrence of the six stellettins could partly provide the chemotaxonomic evidence.A new isomalabaricane triterpene, stellettin N (1), has been isolated together with five known analogues, stellettin H (2), rhabdastrellic acid A (3), stellettin G (4), stellettin D (5), and 22,23-dihydrostellettin D (6), from the Hainan sponge Stelletta sp. The structure of 1 was elucidated on the basis of detailed spectroscopic analysis of its methyl ester (7) and by comparison of NMR data of 7 with those of related known compounds. Compounds 3–8 were evaluated for their inhibitory activity against hPTP1B and the result showed compound 4 had a strong hPTP1B inhibitory activity with IC50 value of 4.1 ± 0.9 μM. Compound 4 also exhibited weak cytotoxicity against A549 and HL-60 cells at a concentration of 10 μM. Furthermore, the chemotaxonomic significance of these compounds was also summarized.