Abstract
The sponge Fascaplysinopsis sp. (order Dictyoceratida, Family Thorectidae) from the west coast of Madagascar (Indian Ocean) is a particularly rich source of bioactive nitrogenous macrolides. The previous studies on this organism led to the suggestion that the latter should originate from associated microsymbionts. In order to evaluate the influence of microsymbionts on lipid content, 10 samples of Fascaplysinopsis sp. were investigated for their sterol composition. Contrary to the secondary metabolites, the sterol patterns established were qualitatively and quantitatively stable: 14 sterols with different unsaturated nuclei, Δ5, Δ7 and Δ5,7, were identified; the last ones being the main sterols of the investigated sponges. The chemotaxonomic significance of these results for the order Dictyoceratida is also discussed in the context of the literature. The conjugated diene system in Δ5,7 sterols is known to be unstable and easily photo-oxidized during storage and/or experiments to produce 5α,8α-epidioxy sterols. However, in this study, no 5α,8α-epidioxysterols (or only trace amounts) were observed. Thus, it was supposed that photo-oxidation was avoided thanks to the natural antioxidants detected in Fascaplysinopsis sp. by both the DPPH and β-caroten bleaching assays.
Highlights
In continuation of our long-standing interest in the chemistry of marine sponges, we have investigated the Madagascar Fascaplysinopsis sp. sponge
We report the isolation of the free sterol fraction from the 10 studied specimens and the investigation of the sterol content by high-performance liquid chromatography coupled to ultraviolet diode array detection (HPLC-UV), gas chromatography coupled with flame ionization detection (GC-FID) and gas chromatography coupled to mass spectrometry (GC-MS) methods to elucidate their chemical composition
The sterol profiles obtained by GC-MS and GC-FID were exactly identical for all 10 studied specimens of Fascaplysinopsis sp
Summary
In continuation of our long-standing interest in the chemistry of marine sponges, we have investigated the Madagascar Fascaplysinopsis sp. sponge (order Dictyoceratida, family Thorectidae).Previous studies on different batches of this sponge, resulted in the isolation and identification of four unprecedented groups of cytotoxic sponge nitrogenous macrolides, i.e., salarins A–J [1,2,3], tulearinsA–C [1,4], taumycins A and B [5], and a fourth group, combining taumycin and salarin, designated tausalarin C [6]. In continuation of our long-standing interest in the chemistry of marine sponges, we have investigated the Madagascar Fascaplysinopsis sp. The structural similarity of the various sponge metabolites of the four groups to microorganism and fungal metabolites (e.g., the cyanobacteria Lyngbia bouillonii metabolites madangolide and laingolide A) [7,8] suggested that these compounds originate from guest microorganisms rather than from the host sponge itself. This notion is supported by the chemical content variations from one collection to the other; Fascaplysinopsis sp. Based on bacterial community studies employing molecular methods such as Denaturing Gradient Gel
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