The Micronesian sponge Oceanapia sp. afforded three pyridoacridine alkaloids: the known compounds kuanoniamine C (1) and kuanoniamine D (2), as well as the new N-deacyl derivative (3) of the kuanoniamines. Compounds 1 and 2 exhibited insecticidal activity toward neonate larvae of the polyphagous pest insect Spodoptera littoralis (LC50 of 156 and 59 ppm, respectively), when incorporated into artificial diet. Both compounds also showed toxicity in the brine shrimp lethality test with a LC50 of 37 micrograms/mL (compound 1) and 19 micrograms/mL (compound 2), respectively. The N-deacyl derivative did not show any remarkable effect in both bioassays. Cytotoxcity of the alkaloids was studied in vitro, using two human cell lines. The new derivative (3) appeared to be active in the same range of concentrations as kuanoniamine C (1) and D (2). The IC50 of 3 was 1.2 micrograms/mL toward HeLa cells and 2.0 micrograms/mL toward MONO-MAC 6 cells. In receptor binding assays compound 2 showed affinity to A1- and A2A-adenosine receptors with Ki values of 2.94 and 13.7 microM, respectively. Compound 1 was less active than compound 2, whereas compound 3 showed no affinity toward adenosine receptors. In addition, compounds 1-3 exhibited moderate affinity to benzodiazepine binding sites of GABAA receptors.
Two new dimeric bromopyrrole alkaloids, nakamuric acid (1) and its corresponding methyl ester (2), have been isolated from the Indopacific sponge Agelas nakamurai along with the known metabolites sceptrin (3), debromosceptrin (4), and ageliferin (5). Their structures were identified by analysis of spectral data. All compounds inhibited the growth of several Gram-positive and Gram-negative bacteria in the agar plate diffusion assay.
Two samples of the marine sponge Stylissa carteri collected in Indonesia yielded two new bromopyrrole alkaloids: debromostevensine (1) and debromohymenin (2), as well as nine other known congeners (3-11). The structures of the new compounds were unambiguously established on the basis of their NMR and mass spectra.
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