New cyclic peroxides from the Philippine sponge Plakinastrella sp

Area of Science:

• Marine Natural Products Chemistry
• Organic Chemistry
• Pharmacognosy

Background:

• Marine sponges, particularly from unexplored regions like the Philippines, are rich sources of novel bioactive compounds.
• Plakinastrella species are known to produce diverse secondary metabolites with potential biological activities.
• Previous studies on related sponges indicated antifungal properties, prompting further investigation into their chemical constituents.

Purpose of the Study:

• To isolate and characterize new chemical entities from a Plakinastrella sponge species collected in the Philippines.
• To determine the structures and absolute stereochemistry of the isolated compounds.
• To evaluate the biological activity of the novel metabolites, particularly their antifungal potential.

Main Methods:

• Hexane extraction of the sponge biomass.
• Chromatographic separation techniques (e.g., column chromatography) for isolating compounds.
• Spectroscopic analyses (NMR, MS) for structure elucidation.
• Chemical interconversion and Mosher's method for stereochemical determination.

Main Results:

• Isolation of three new cyclic peroxides (compounds 5-7) and one new carboxylic acid ester (compound 8).
• Complete structural elucidation of compounds 5-8 using comprehensive spectral data interpretation.
• Determination of the absolute stereochemistry of peroxide 6.
• Assessment of antifungal activity against Candida albicans revealed that minor metabolites 5-8 are essentially inactive.

Conclusions:

• The hexane extract of the studied Plakinastrella sponge yielded novel cyclic peroxides and a carboxylic acid ester.
• While major compounds from this sponge exhibited antifungal activity, the newly isolated minor metabolites lack significant bioactivity.
• This study expands the knowledge of chemical diversity within the Plakinastrella genus and highlights the importance of exploring minor constituents for unique structures.