R. Gomez

Localization and ecological significance of oroidin and sceptrin in the Caribbean sponge Agelas conifera

The Caribbean sponge Agelas conifera was found to produce a mixture of previously described bromopyrrole alkaloids of which oroidin (1) and sceptrin (2) were predominant. This sponge harboured large populations of heterotrophic bacteria but no photosynthetic symbionts (cyanobacteria). However, 1 and 2 were not associated with the bacteria but with the sponge cells as shown by their distribution in enriched cell fractions obtained by differential centrifugation and Ficoll density gradients. Spherulous cells, found in great abundance in the sponge ectosome, were assumed to be involved in the production of 1 and 2. The target compounds were detected, although in small amounts, in short-term cultures of sponge cells, validating the possibility of a continuous cell culture source. Laboratory assays showed that organic sponge extracts affected the behaviour of the coral Madracis mirabilis in causing closure and retraction of the polyps at concentrations of the combined compounds 1 and 2 (1:3.3) as low as 0.7 mg/l (0.0125% of the concentration in whole sponges). At higher concentrations (1.4 mg/l) no recovery of the polyps occurred. The extracts, at almost natural concentrations of 1 and 2, deterred feeding by the predatory reef fish Stegastis partitus, supporting other reported research. In field experiments, wounding induced a sharp increase of 1 and 2 in the sponge tissues but prolonged predator exclusion by caging and forced confrontation with coral neighbours did not yield measurable changes in 1 and 2 concentrations. All sponges were found to release measurable amounts of bromopyrrole alkaloids in seawater conditioned for 30 min. Crude and fractionated sponge extracts and pure sceptrin (2) were active against bacteria, yeast and filamentous fungi. Taken together, these results support a role of oroidin (1) and sceptrin (2) in defence mechanisms against predators and possibly against space competitors and invading and fouling organisms.

Preliminary Ecological Studies on Sponges of the Genus Agelas Spp.

The influence of environmental factor, namely depth and sponge-coral interactions as well as the effects of infliction of standardized damages on the production of bromopyrrolic alkaloids isolated from the sponges Agelas dispar and Agelas conifera were analysed.

Preliminary Antifungal Activity of Some Sponges from Indonesia and Oman

80 methanolic extracts from sponges of Indonesia and Oman were screened for antifungal activity against ten strains fungi: Botrytis cinerea, Cladosporium cucumerinum, Fusarium oxysporum, Penicillium expansum, Rhizopus oryzae, Trichoderma harzianum, Aspergillus niger, Mucor pusillus, Absidia corymbifera and Absidia ramosa. The bromopyrrolic alkaloids hymenidin and sceptrin isolated from the sponges Agelas dispar and Agelas conifera, respectively, were also tested against the above fungi.