Endophytic fungi are those fungi that colonizes the inner tissues of a host which could be a plant or an animal, exhibiting mutual benefits, where the host organism provides a proper medium for the growth of the fungi and in turn the growing fungal species would provide the host with bioactive compounds enabling it to withstand unfavorable conditions and mediating the different ecological interactions. Endophytic fungi derived from marine ecosystems had received much attention in the last two decades with more than one thousand fungal species isolated from marine habitats. Cephalosporin C was the first bioactive molecule isolated from a marine-derived fungus Cephalosporium sp. since then they had proven to be a fabulous source of bioactive secondary metabolites.

The fungal strain Aspergillus sp. AV-2 was isolated from the inner healthy leaves of mangrove plant Avicennia marina collected at Hurghada, Egypt. Then, a pure isolate was cultivated on solid rice medium to find out its specific secondary metabolites. A new phenyl pyridazine derivative (1) and a new prenylated benzaldehyde derivative (2) were isolated together with fourteen known compounds.