Marine natural products extracted from sponges represent a new source for drug discovery. Here we describe a simple method for preparing aqueous extracts from 7 Mediterranean demosponges, which allowed the extraction of water-soluble compounds, such as proteins by homogenization of sponge tissue in phosphate buffered saline (PBS).The comparative analysis by SDS-PAGE showed differences in number of bands, bandwidth and intensity among the sponges analyzed. The PAS/silver staining revealed a substantial and different glycoprotein assortment among the demosponges studied.To further study the biological activities present in the sponge extracts, we determined the non-cytotoxic doses on four different mammalian cell types demonstrating that the optimal non-cytotoxic doses were cell type- and extract-dependent.In conclusion, the extraction method described in this paper represents a fast and efficient procedure for the extraction of water-soluble proteins from marine sponges. Furthermore, the cell viability data suggest the feasibility of this method for the direct in vitro cell-based assays.