Browsing by Author "Gerwick, William H."
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- Antitumor activity of hierridin B, a cyanobacterial secondary metabolite found in both filamentous and unicellular marine strainsPublication . Leão, Pedro N.; Costa, Margarida; Ramos, Vitor; Pereira, Alban R.; Fernandes, Virgínia C.; Domingues, Valentina F.; Gerwick, William H.; Vasconcelos, Vítor; Martins, RosárioCyanobacteria are widely recognized as a valuable source of bioactive metabolites. The majority of such compounds have been isolated from so-called complex cyanobacteria, such as filamentous or colonial forms, which usually display a larger number of biosynthetic gene clusters in their genomes, when compared to free-living unicellular forms. Nevertheless, picocyanobacteria are also known to have potential to produce bioactive natural products. Here, we report the isolation of hierridin B from the marine picocyanobacterium Cyanobium sp. LEGE 06113. This compound had previously been isolated from the filamentous epiphytic cyanobacterium Phormidium ectocarpi SAG 60.90, and had been shown to possess antiplasmodial activity. A phylogenetic analysis of the 16S rRNA gene from both strains confirmed that these cyanobacteria derive from different evolutionary lineages. We further investigated the biological activity of hierridin B, and tested its cytotoxicity towards a panel of human cancer cell lines; it showed selective cytotoxicity towards HT-29 colon adenocarcinoma cells.
- Biosynthesis-assisted structural elucidation of the bartolosides, chlorinated aromatic glycolipids from cyanobacteriaPublication . Leão, Pedro N.; Nakamura, Hitomi; Costa, Margarida; Pereira, Alban R.; Martins, Rosario; Vasconcelos, Vítor; Gerwick, William H.; Balskus, Emily P.The isolation of the bartolosides, unprecedented cyanobacterial glycolipids featuring aliphatic chains with chlorine substituents and C-glycosyl moieties, is reported. Their chlorinated dialkylresorcinol (DAR) core presented a major structural-elucidation challenge. To overcome this, we discovered the bartoloside (brt) biosynthetic gene cluster and linked it to the natural products through in vitro characterization of the DAR-forming ketosynthase and aromatase. Bioinformatic analysis also revealed a novel potential halogenase. Knowledge of the bartoloside biosynthesis constrained the DAR core structure by defining key pathway intermediates, ultimately allowing us to determine the full structures of the bartolosides. This work illustrates the power of genomics to enable the use of biosynthetic information for structure elucidation.
- Isolation of Hierridin B from a culturable Cyanobium sp. strain isolated from the Portuguese coastPublication . Leão, Pedro N.; Pereira, Alban R.; Costa, Margarida; Ramos, Vítor; Martins, Rosário; Gerwick, William H.; Vasconcelos, VitorCyanobacteria are a genetically diverse group of phototrophic prokaryotes. On a secondary metabolite perspective, however, filamentous and benthic forms have been the major sources of compounds isolated from these organisms. Nevertheless, unicellular free-living, planktonic cyanobacteria also contain enzymatic machinery for secondary metabolite biosynthesis.