Marine sponges (Porifera) have been the central focus of the research for the discovery of biologically-active secondary metabolites. The sponges of the genus Petrosia inhabit various regions and contain a variety of biologically active natural products such as polyacetylenes, sterols, meroterpenoids, and alkaloids. The work envisaged concerns the sponges of the genus Petrosia resulting from the order of Haplosclerida. Indeed, this taxonomic group reveals families of very particular molecules. They are the source of acetylenic compounds, fatty acids, sterols, quinolizidine derivatives and pyridoacridines widely used in the marine environment. Linear acetylenic derivatives very diverse in this genus are known for their interesting biological activities. They are considered as chemotaxonomic markers of the order Haplosclerida which is at the origin of one hundred identified acetylenic derivatives. Their biological functions would be to protect sponges against fungi, bacteria, larval fixation and fish. In addition, several other biological properties have been demonstrated for these molecules: anti-HIV by inhibition of proteases and reverse transcriptase, inhibition of H+, K+ - ATPases, immunosuppressive and anti-cancer activities. The studies conducted during this work have involved various methods and techniques such as extraction, fractionation and purification methods. The crude aqueous extract of freeze-dried Petrosia ficiformis was used to evaluate in vitro antifungal activity on an agar medium by measuring the growth of the radial diameter of the Penicillium digitatum colony, Aspergillus fumigatus and Rhizopus stolonifer. This represents an alternative for controlling phytopathogens and could be used as an antagonist for other pathogens or as a source of biofungicides.