New bromopyrrole alkaloids from a Dictyonella sp. sponge

The recent investigation of new bromopyrrole alkaloids by a former MSc. student, Renata Torres, resulted in the discovery of 4-debromooroidin (1), 4-debromougibohlin (2), 5-debromougibohlin (3) and 5-bromopalau’amine (4) from the MeOH extract of the sponge Dictyonella sp. These new alkaloids were isolated along with the known hymenidin (5) and (+)-monobromoisophakellin (6). Curiously, the bromination pattern of compounds 1–4 is rather unusual for the marine sponge brominated pyrrole alkaloids. Usually, bromination at C-3 is more frequently observed for these compounds. The alkaloids were tested as proteasome inhibitors by the group of Dr. Daniela Trivella, researcher at the LNBio Laboratory at CNPEM. Results showed that 5-bromopalau’amine (4) was the most active alkaloid, in agreement with previous results observed for these metabolites when tested as proteasome inhibitors. Samples of the sponge were made available by a group of researchers of the Rio de Janeiro Botanical Garden and Federal University of Rio de Janeiro, who collected the animal during an expedition at the mouth of the Amazon river. Spectroscopic data collection and analyses were performed collaboratively with Prof. Antonio G. Ferreira at the Federal University of São Carlos and with Dr. David E. Williams and Prof. Raymond J. Andersen at the University of British Columbia. This investigation was published in the Journal of Natural Products, and corresponds to the MSc dissertation project of Renata Torres.