Antimicrobial and cytotoxic effects of the most active betulin derivatives at 50 µM concentration (thresholds: antimicrobial activity >70%, cytotoxicity >50%).

<p>Values represent the mean ± SD of 3–6 replicates. Inhibitory effects of the most active samples are in bold. Primary screening results for all tested compounds are available in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102696#pone.0102696.s002" target="_blank">Tables S1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102696#pone.0102696.s003" target="_blank">S2</a>.</p

Antimicrobial activity in host-pathogen co-culture assay.

<p>The assay was based on <i>S. aureus</i> infected HL cell line. Dose-response results for a) ciprofloxacin) and b) 28-<i>O</i>-(<i>N</i>-acetylanthraniloyl)betulin (<b>5</b>).</p

Chemical structures of betulin and the most active betulin derivatives.

<p>Betulin (<b>1</b>), betulinyl 28-carboxymethoxycarvacrolate (<b>4</b>), 28-<i>O</i>-(<i>N</i>-acetylanthraniloyl)betulin (<b>5</b>), betulinic aldehyde (<b>18</b>), betulonic acid (<b>23</b>), betulin-28-oxime (<b>31</b>), and heterocyclic derivatives with 1,3-dioxol-5-yl (<b>35</b>), 3-nitrophenyl (<b>38</b>) and ethyl (<b>43</b>) attached to the nitrogen atom in the triazolo ring.</p

Cytotoxic effect of selected betulins on mammalian cells (Huh-7) after 24 h exposure at different concentrations.

<p>A) betulinic aldehyde (<b>18</b>), B) betulin-28-oxime (<b>31</b>) and C) hetero cycloadduct (<b>43</b>).</p

Baltic cyanobacteria – a source of biologically active compounds

<div><p>Cyanobacteria are effective producers of bioactive metabolites, including both acute toxins and potential pharmaceuticals. In the current work, the biological activity of 27 strains of Baltic cyanobacteria representing different taxonomic groups and chemotypes were tested in a wide variety of assays. The cyanobacteria showed strain-specific differences in the induced effects. The extracts from <i>Nodularia spumigena</i> CCNP1401 were active in the highest number of tests, including protease and phosphatase inhibition assays. Four strains from Nostocales and four from Oscillatoriales increased proliferation of mitogen-stimulated human T cells. In antimicrobial assays, <i>Phormidium</i> sp. CCNP1317 (Oscillatoriales) strongly inhibited the growth of six fouling Gammaproteobacteria. The growth of monocotyl <i>Sorghum saccharatum</i> was inhibited by both toxin-producing and ‘non-toxic’ strains. The Baltic cyanobacteria were also found to be a rich source of commercially important enzymes. Among the 19 enzymatic activities tested, alkaline phosphatase, acid phosphatase, esterase (C4 and C8), and naphthol-AS-BI-phosphohydrolase were particularly common. In the cyanobacterial extracts, different peptides which may have been responsible for the observed effects were identified using LC-MS/MS. Their structures were classified to microcystins, nodularins, anabaenopeptins, cyanopeptolins, aeruginosins, spumigins and nostocyclopeptides.</p></div