•Isolation and structure elucidation of sponge natural products.•Nucleosides from marine invertebrates.•Unusual isoguanosine derivatives.After a chemical screening of subtidal sponges from the Northeastern Atlantic, Clathria (Microciona) strepsitoxa (Poecilosclerida: Microcionidae) was selected for deeper investigation. This first chemical study led to the identification of two new 8-oxoisoguanosine derivatives. The structure elucidation was performed after extensive analyses of spectroscopic (1D and 2D NMR) and HR-ESIMS data and no significant antimicrobial or cytotoxic activity was detected.Download high-res image (144KB)Download full-size image

Three new diterpenes named gersemiols A–C (1–3) and a new eunicellane diterpene, eunicellol A (4), have been isolated together with the known sesquiterpene (+)-α-muurolene (5) from the Arctic soft coral Gersemia fruticosa. The name gersemiane was assigned to the rare and unnamed diterpene skeleton of compounds 1–3 corresponding to 4-isopropyl-1,5,8a-trimethyltetradecahydrophenanthrene. The chemical structures were elucidated on the basis of extensive spectroscopic analysis (HR-ESIMS, 1D and 2D NMR) as well as coupling constant calculations for the determination of the relative configurations. All compounds were tested for their antimicrobial activity against several bacteria and fungi and eunicellol A was found to exhibit moderate and selective antibacterial activity.

Previous works with autumnalamide reported that Store Operated Calcium (SOC) channels were blocked through mitochondrial modulation. In the present paper we studied the effect of autumnalamide on ionomycin Ca2+ fluxes. Thus, autumnalamide did not modify ionomycin-sensitive intracellular pools while the ionomycin-induced Ca2+ influx was blocked with similar potency whether the incubation was done before or after ionomycin-sensitive pools depletion. Nevertheless, autumnalamide was not able to inhibit ionomycin-induced Ca2+ influx once the membrane channels were activated. Moreover, the compound efficiently inhibited flufenamic acid (FFA) Ca2+ release induced in this organelle but no the next influx. Since in previous work the effect of autumnalamide was inhibited by cyclosporine A (CsA), structures that target this drug were studied. Therefore, the affinity of autumnalamide for cyclophilin D (Cyp D) was examined. The KD obtained for Cyp D- autumnalamide was 1.51 ± 1.399. Moreover, the KD for Cyp A- autumnalamide was calculated. The peptide had a similar order of Cyp A binding affinity than CsA (8.08 ± 1.23 and 6.85 ± 1.1 μM respectively). After testing autumnalamide-binding capacity for Cyp A, the activity of this compound on Cyp A pathway was tested. Thus, the effect on interleukin (IL)-2 release on activated T-lymphocytes was checked. Autumnalamide was able to reduce IL-2 levels near to T cells in resting conditions. Next, the effect over calcineurin and NFATc1 was also evaluated. While CsA inhibits both calcineurin and NFATc1, autumnalamide did not produce any effect. From these results we can conclude that, autumnalamide targeted mitochondrion and prevent T-cells from IL-2 production through the modulation of SOC Ca2+ channels.