Abstract Marine algae have been the focus of important studies over the past fifty years, with a considerable number of components important to chemists and taxonomists having been isolated and characterized. The scientific data available on Sargassum polyceratium are extremely limited. The objective of the present study was to evaluate the antinociceptive activity of an ethanol extract of S. polyceratium and to isolate its components. Intraperitoneal treatment with ethanol extract of S. polyceratium reduced the number of acetic acid-induced writhes and the amount of time spent in paw-licking in the second phase of the formalin test. Ethanol extract of S. polyceratium also reduced the amount of time spent in paw-licking in the glutamate test; however, there was no difference in the reaction time in the hot plate test at any of the doses tested. The chemical components isolated from ethanol extract of S. polyceratium were identified using one- and two-dimensional spectroscopic methods such as infrared spectroscopy, mass spectrometry and 1H and 13C nuclear magnetic resonance spectroscopy. The analytical results were also compared with data obtained in the literature. The following porphyrin derivatives were isolated from S. polyceratium: 132-hydroxy-(132-R)-pheophytin-a, 132-hydroxy-(132-S)-pheophytin-a, pheophytin-a, and the steroid fucosterol. The present results indicate that the ethanol extract of S. polyceratium has antinociceptive activity. In addition, four new substances were isolated from the species evaluated.

The new dibromotyrosine derivative 3,5-dibromo-4-[3'dimethylamonium]propoxyphenyl]-N,N,N-trimethylethanamonium, here referred to as aplysfistularine (1), was isolated from the marine sponge Aplysina fistularis along with 2-(3,5-dibromo-4methoxyphenyl)-N,N,N-trimethylethanamonium (2), aplysterol (3) and 24,28-didehydroaplysterol (4). Their identification was performed by mass spectrometry, infrared, ¹H and 13C NMR, and by comparison with literature data. Compound 2 and the mixture of 3 and 4 were tested in vitro (inhibitory activity) with supercoiled DNA relaxation techniques, and showed inhibitory activity on human DNA topoisomerase II-α. Compound 1 was not tested due to paucity of the material.