Protocol to isolate sponge-associated fungi from tropical waters and an examination of their cardioprotective potential

Fungi represent an essential component of biodiversity not only because of their high species richness at multiple scales, but also because of their ecological, evolutionary and socio-economic significance. Despite poorly understood natural history and uncertain estimates of diversity, marine fungi have been identified as a major source of new natural products with pharmacological applications. The aims of this study were (1) to characterize fungi associated with marine sponges in protected areas of the Pacific and Caribbean coasts of Panama, and (2) to examine their effects through radioligand binding assays on endothelin ET_A (ET_A) and neuropeptide Y Y₁ (Y₁) receptors, which provide an indication of cardioprotective potential. A total of 369 marine sponges were collected in areas of high biodiversity along the Panamanian coasts, including 156 from the western Caribbean and 213 from the eastern Pacific. From these, 2,747 and 2,263 fungal isolates were recovered, respectively, with variable isolation frequencies when sponge fragments were cultivated on five media. After determining the seasonality, geographic stucture, and taxonomic diversity of these fungal assemblages, we identified five strains that inhibited by > 50% the binding of [3H] BQ-123 and one the binding of [³H] neuropeptide Y to the ET_A and Y₁ receptors, respectively, at 100 μg/ml. Further studies are required to determine whether these interactions are agonistic or antagonistic. Drawing from our methods for isolating and screening these fungi we propose a general protocol for capturing, cataloguing, and assessing the pharmacological potential of previously undiscovered fungi associated with marine sponges.